EP4469651A1

EP4469651A1 - Projectile resistant wall assembly

Info

Publication number: EP4469651A1
Application number: EP22703833.8A
Authority: EP
Inventors: Camilla LIDGREN
Original assignee: Knauf Gips KG
Current assignee: Knauf Gips KG
Priority date: 2022-01-28
Filing date: 2022-01-28
Publication date: 2024-12-04
Also published as: MX2024007548A; WO2023143691A1; IL314339A; JP2025507229A; JP7844798B2

Abstract

The invention relates to a wall assembly that is resistant to bullet projectiles. The assembly is useful for partitions as well as for exterior walls. The wall assembly comprises a sub-structure made of framing members with building boards attached to two opposing sides of the sub-structure to form a first side of a wall and a second side of a wall, wherein - the first side of the wall comprises at least one layer S1LF of at least one gypsum fiberboard, wherein the at least one layer S1LF has a total thickness of at least 25 mm - the first side of the wall further comprises at least one layer S1LG of at least one gypsum board, wherein any of the gypsum boards of layer S1LG comprises 1 wt.-% to 5 wt.-% polyvinyl acetate based on its solids content, relative to the weight of the gypsum and - the second side of the wall comprises at least one layer S2LF of at least one gypsum fiberboard, wherein the at least one layer S2LF has a thickness of at least 25 mm and a cavity is present between the first side and the second side, wherein the cavity has a thickness of at least 40 mm and is filled with air or an insulation material.

Description

Projectile resistant wall assembly

The invention relates to a wall assembly that is resistant to bullet projectiles. Particularly, the wall assembly is laid out to resist perforation by ammunition classed FB4 to FB7 according to EN 1522:1998. The assembly is useful for partitions as well as for exterior walls.

Bullet projectile resistant structures are made with many materials. A brick wall of a thickness of 24 cm, for example, is projectile resistant. However, the brick wall has many disadvantages compared to a drywall construction. Herein, the term drylining or drywall structure or drylining or drywall construction denotes any structure or building construction with a frame substructure with building panels or boards mounted thereto. A drylining wall has the advantage that it built faster and weighs less compared to a brick wall. Particularly non-load bearing walls can be built as drylining construction. Load-bearing walls typically require special framing members. A typical drylining construction comprises timber or metal framing with building boards such as plasterboard, gypsum fiberboard, oriented strand board etc. attached to two opposing sides of the framing member.

Handgun bullet projectile resistant drylining (drywall) structures are known in the state of the art. A conventional handgun bullet projectile resistant wall structure comprises a substructure of drylining studs (metal studs). The upright studs are fixed to metal rails which are mounted horizontally on the floor and ceiling. The upright studs comprise parallel extending flange portions having an outer surface capable of attaching boards (building panels) thereto. Both parallel extending flanges are connected via a web portion. The parallel extending flanges and the base portion can be arranged in a C-shape or a U-shape, for example.

To achieve the handgun or rifle bullet projectile resistance of a partition wall, EP1807583B1 and EP 3283714B1 disclose arranging gypsum fiberboards inside the substructure, i.e. in the space between adjacent studs. This means that the gypsum fiberboards are positioned such that their edges contact the web region of a metal stud, which would typically correspond to a wide face of a non-square timber stud. It is uncommon to fix gypsum fiberboards to the flange portions of a metal stud because of their high weight compared to a regular gypsum board, also known as a plasterboard. In

CONFIRMATION COPY previous constructions, gypsum fiberboards were attached to the flanges of the studs by adhesive or screws. Screwing was only possible, if the gypsum fiberboards were predrilled. Arranging gypsum fiberboards inside the substructure is a tricky and timeconsuming process, because it is extremely difficult to place the heavy boards accurately between the studs.

Additionally, known drylining structures with resistance to rifle bullets typically rely on a metal sheet arranged between gypsum-based building boards on both sides of the substructure. Metal sheets are not only more costly than gypsum boards or gypsum fiberboards, but they are also difficult to handle and integrate into the drylining assembly.

The bullet resistance of structures is rated by EN 1522. Known structures provide projectile resistance performance of class FB4 and FB5 according to DIN EN 1522:1998. FB4 is the highest class of protection against handguns and FB5 is the lowest class of protection for larger caliber rifles. FB4 (BR4) resists 3 shots of a handgun .44 Magnum FJ (Full Metal Jacket) I FN (Flat Nose) I SC (Soft Core) of the weight 15.6 ± 0.1 g from a range of 5.00 ± 0.5 m having a velocity of 440 ± 10 m/s and an impact energy of 1510 J. FB5, which is the first class for the resistance against rifle bullets. FB5 structures resist three shots from a rifle in caliber 5.56 x 45 mm NATO FJ (Full Metal Jacket - copper alloy jacket) I PB (Pointed Bullet) /SCP (Soft Core (lead) & Steel Penetrator) of the weight 4.0 ± 0.1 g from a range 10.00 ± 0.5 m having a velocity of 950 ± 10 m/s.

Thus far no drylining constructions were able to achieve FB6 or FB7. FB6 structures resist three shots from a rifle in caliber 5.56 x 45 mm NATO FJ (Full Metal Jacket - copper alloy jacket) I PB (Pointed Bullet) /SCP (Soft Core (lead) & Steel Penetrator) of the weight 4.0 ± 0.1 g from a range 10.00 ± 0.5 m having a velocity of 950 ± 10 m/s. As well as three shots from a rifle in caliber 7.62x51 mm NATO FJ (Full Metal Jacket full steel jacket, plated) I PB (Pointed Bullet) /SCP (Soft Core (lead)) of the weight 9.5 ± 0.1 g from a range 10.00 ± 0.5 m having a velocity of 830 ± 10 m/s. FB7 structures resist three shots from a rifle in caliber 7.62 x 51 mm NATO FJ (Full Metal Jacket - copper alloy jacket) I PB (Pointed Bullet) I steel hard core (mass 3.7 ± 0.1 g, hardness more than 63 HRC)) of the weight 9.8 ± 0.1 g from a range 10.00 ± 0.5 m having a velocity of 820 ± 10 m/s.

There is a need to simplify the construction of bullet resistance drylining structures to make them more economical. There is also a strong need for drylining constructions with increased bullet resistance compared to the state of the art. Rifles of various calibers play a significant role in killing sprees and terrorizing assaults. Hence, an improved projectile resistance for load-bearing and non-loadbearing, interior and exterior walls is desirable, particularly for public buildings (schools, police stations, court buildings, prisons, embassies, shops etc.) as well as private housing, which frequently has high security requirements to protect individuals and/or property. It is therefore the object of the invention to provide a wall assembly, which can resist handgun and/or rifle bullets and is more economical compared to structures mentioned in the prior art. It is further the object of the invention to provide a wall assembly, which is easier to assemble than those mentioned in the prior art. Additionally, less costly material is desirable. It is a further object of the invention to provide a wall assembly with projectile resistant properties, which renders itself to decorative coating such as a layer of plaster, render or wallpaper. Most importantly, it is the object of the invention to provide a wall assembly, which has a bullet resistance performance for rifle bullets (of a higher class, higher caliber than disclosed in the prior art), with all the advantages of drylining constructions.

The problem is solved by a wall structure with the features of claim 1. These features provide a projectile resistance with which the demands of EN 1522:1998 can be met. Preferred aspects form the subject matter of the dependent claims.

Specifically, the problem is solved by a wall assembly comprising a sub-structure made of framing members with building boards attached to two opposing sides of the substructure to form a first side of a wall and a second side of a wall, wherein

- the first side of the wall comprises at least one layer S1 LF of at least one gypsum fiberboard, wherein the at least one layer S1 LF has a total thickness of at least 25 mm

- the first side of the wall further comprises at least one layer S1 LG of at least one gypsum board, wherein any of the gypsum boards of layer S1 LG comprises 1 wt.-% to 5 wt.-% polyvinyl acetate based on its solids content, relative to the weight of the gypsum and

- the second side of the wall comprises at least one layer S2LF of at least one gypsum fiberboard, wherein the at least one layer S2LF has a thickness of at least 25 mm and

- a cavity is present between the first side and the second side, wherein the cavity has a thickness of at least 40 mm and is filled with air or an insulation material.

In the context of this invention, “at least one” can mean one, two, three, four or even more than four.

Optionally, the second side may further comprise at least one layer S2LG of at least one gypsum board.

A wall typically has two main surfaces or two main sides. The inventive wall assembly also comprises two sides, a first side and a second side. The first side and the second side can be essentially parallel to one another. The sub-structure or support frame is made of framing members. These framing members can be made of metal or timber. Vertical framing members are typically referred to as studs and horizontal framing members are typically referred to as rails, tracks or beams. A metal framing member typically comprises two parallel flanges connected by a web, wherein there is roughly a 90° angle between each flange and the web. The building boards are attached to a flange of the framing member. While U-shaped studs could be used as vertical framing members, C-shaped studs are preferred as they offer more stability. The vertical (metal) framing members are typically positioned in horizontal framing members such as U-shaped tracks or rails.

Timber framing members typically have four faces, all at right angles to one another. The building boards are attached to two opposing faces of the framing member. Typically, the two adjacent faces of a framing member have a different width. The building boards are generally attached to the face/s with the smaller width.

The vertical framing members (metal or timber) are frequently positioned 450 mm or 600 mm or 625 mm apart. However, other distances between the vertical framing members are also possible.

A gypsum fiberboard is a type of building board with a gypsum core and typically comprises > 70 wt.-%, preferably 75 wt.-% to 98 wt.-% calcium sulfate dihydrate based on the weight of the board. In contrast to gypsum boards, the gypsum fiberboards have a higher fiber content, mainly cellulose fibers. Generally, a gypsum fiberboard contains 6 wt.-% to 25 wt.-% fibers, preferably 8 wt.-% to 16 wt.-% fibers based on the gypsum in the board. A standard production line for gypsum boards cannot process this high fiber content, which is one of the reasons why gypsum fiberboards are manufactured by different processes. The cellulose fibers in the gypsum fiberboard usually stem from recycled paper, which is mixed with water and added to the gypsum slurry as paper pulp. In addition to calcium sulfate dihydrate and cellulose fibers, it can contain other additives, such as glass fibers, setting additives or rheology modifiers. The additives are generally dosed in relation to the stucco (calcium sulfate hemihydrate) and given as weight percent based on the weight of the stucco. In the finished board, the relative amount of additive(s) is based on the weight of the gypsum (calcium sulfate dihydrate). Since calcium dihydrate contains more water of crystallization, its molecular weight differs by a factor of approximately 1 .2. As a consequence, the relative amounts of additives shift slightly, i.e. they diminish marginally, compared to the original relative amounts based on the stucco. Gypsum fiberboards do not require liners. They are generally manufactured without any liners. Typical dimensions of gypsum fiberboards are 600 mm by 1200 mm or 600 mm by 600 mm for boards with a thickness of 25 mm to 30 mm. Thinner gypsum fiberboards (e.g. thickness 10 mm to 15 mm) can be sized 1200 mm by 2400 mm. A gypsum board (frequently also referred to as plasterboard) is another type of building board. Gypsum boards comprise a gypsum core, which typically comprises > 70 wt.-%, preferably 75 wt.-% to 98 wt.-% calcium sulfate dihydrate based on the weight of the board. In addition to calcium sulfate dihydrate, it can contain other additives, such as glass fibers or cellulose fibers, setting additives or rheology modifiers. If fibers are present, they are typically present in at most 3 wt.-% based on the weight of the gypsum in the gypsum board, preferably at most 1 .5 wt.-%. Preferably, more glass fibers are incorporated than cellulose fibers. The gypsum board of this invention comprises at least polyvinyl acetate as additive. Analogous to the gypsum fiberboards, the additives for gypsum boards are generally dosed in relation to the stucco. To be based on the gypsum present in the finished board, their relative amounts need to be adjusted as described above. Like most gypsum boards, the gypsum board comprising polyvinyl acetate also comprises liners on both main surfaces or faces. These liners increase the overall strength of the board. They can be paper liners or woven or non-woven mats. Most preferably, the gypsum board comprising polyvinyl acetate has paper liners. The liners can have a grammage of 160 g/m² to 250 g/m², frequently one face has a liner of a higher grammage than the other face. Paper liners are advantageous, because they are easier to handle, cheaper and can be recycled more easily. Woven or non-woven mats, on the other hand, can be chosen, if e.g. hydrophobization or mold-resistance are important.

As an exterior wall, the inventive wall assembly can receive additional cladding (with or without insulation material) as fagade. Alternatively, the inventive wall assembly can be built inside an existing exterior wall or fagade. Additionally, the inventive wall assembly may be used as ceiling or flooring element for e.g. a projectile resistant box or a projectile resistant shelter.

Although not a main part of this invention, cement boards comprising polyvinyl acetate and/or cement fiberboards could be used in place of or in addition to the gypsum boards and/or gypsum fiberboards, respectively.

In a wall assembly the various building boards are arranged in layers, e.g. layers of one, two or more gypsum boards and/or layers of one, two or more gypsum fiberboards. Typically, the first layer of building boards is attached directly to the sub-structure and subsequent layers of building boards are attached to an underlying layer of building boards. However, it is also conceivable that all layers are attached to the sub-structure.

At least two layers of building boards, S1 LF and S1 LG, are attached on one side of the sub-structure to form a first side of the wall and at least one layer of building boards, S2LF, is attached to the opposing side of the sub-structure to form the second side of the wall. In its most minimal form, one layer can consist of only one building board. In many cases, the opposing sides (of the wall assembly), i.e. the first side and the second side, will be essentially parallel to one another.

According to the invention, the layers S1 LF and/or S2LF can consist of one, two or more sub-layers of the same material. To be considered part of the same layer, the sub-layers, i.e. the gypsum fiberboards are in direct contact with one another without being separated by another material. For example, S1 LF could consist of one sub-layer of 28 mm thick gypsum fiberboards. It could also consist of two 12.5 mm thick sub-layers of gypsum fiberboards stacked on top of one another to make up a total thickness of at least 25 mm, as a further example.

The total thickness of S1 LF and/or S2LF can vary in other embodiments. A maximum thickness of 80 mm for S1 LF and/or S2LF is preferable for most applications. More preferably, S1 LF and/or S2LF are 25 mm to 70 mm thick.

Similarly, the layer S1 LG and/or, if present, S2LG can consist of one, two or more sublayers of boards of the same material. To be considered part of the same layer, the sublayers (in this case gypsum boards) are in direct contact with one another without being separated by a different material. The liners are considered being part of the gypsum board and are therefore not considered to be a different material. For example, S1 LG and/or S2LG can each consist of 2 sub-layers. If each sub-layer has a thickness of 9 mm, the total thickness of this layer would be 18 mm. Other typical thicknesses for a sub-layer are 12.5 mm or 15 mm. Preferably, the layer S1 LG and/or, if present, S2LG have a total thickness of at least 12 mm. A maximum thickness of 60 mm for S1 LG and/or S2LG is preferable for most applications, needed, the mentioned layers can be at most 60 mm thick. More preferably, S1 LG and/or S2LG are 12 mm to 50 mm thick.

Thus, the total thickness is meant to denote the thickness of one, two or more sub-layers of building boards of the same material that are in direct contact with one another, whereby direct contact in terms of this invention means that these layers are attached to one another with attachment means and are not separated by another material along the contacting plane. The only material present along the contacting plane can be the attachment means or a thin layer of air, which can be construction related. Preferably the thin layer of air is < 2 mm thick, more preferably < 1 mm thick. If present, the thin layer of air will mostly be unintentional. In general, the thicknesses of the sub-layers are summed up to yield the total thickness.

The cavity is positioned between a layer of building board(s) on the first side and layer of building board(s) on the second side of the wall assembly. More specifically, it is positioned between the innermost layer of building board(s) on the first side and the innermost layer of building board(s) on the second side, wherein the term “innermost” denotes the building board of a side closest to the sub-structure or framing member. Preferably, the cavity corresponds to the space between adjacent framing members. Since the cavity’s thickness corresponds to the distance between a layer of building board(s) on the first side and a layer of building board(s) on the second side, the cavity’s thickness preferably corresponds to the width of the framing member’s web, if metal framing members are used. If timber framing members are used, the cavity preferably corresponds to the width of the framing member. It is essential that the cavity is not filled or is filled with a material of a low density. Low density means, that the cavity is filled with a material of at most 150 kg/m³, preferably at most 50 kg/m³, most preferably 0.8 kg/m³ to 50 kg/m³. Aerographene has a density of 0.2 kg/m³, air has a density of 1 .2 kg/m³, an insulation material such as glass wool has a density of 30 kg/m³. Other suitable insulation materials can be e.g. glass wool, rock wool, wood wool, polystyrene. The cavity’s thickness can be at most 200 mm. Preferably, the cavity’s thickness is 60 mm to 150 mm.

The disclosed assembly yields the following advantages:

- It is easy to assemble.

- It is economical in that assembly time is reduced. For example, it requires no adhesive, no placement of heavy fiberboard layers between studs, no steel plate.

- It provides a better basis for decorative coats such as a layer of plaster or wallpaper compared to the prior art, if the gypsum board is used as outermost layer.

It is noted that any aspect and/or feature of the invention that is individually disclosed in this document and/or in the claims may be commonly realized with one, two, more or all of the other aspects and/or features in respective embodiments of the invention, as far as there is no technical reason against such combinations.

In a preferred embodiment of the invention, the second side further comprises at least one layer S2LG of at least one gypsum board, wherein all of the gypsum boards of layer S2LG comprise 1 wt.-% to 5 wt.% polyvinyl acetate based on its solids content, relative to the weight of the gypsum in the board. The layer S2LG has the advantage that both sides of the wall assembly can achieve the same protection against projectiles. Also, S2LG provides a better basis for decorative coats such as a layer of plaster or wallpaper.

Advantageously, any, some or all of the gypsum boards of layer S1 LG and/or S2LG further comprise glass fibers, preferably 0.5 wt.-% to 2 wt.-% glass fibers, more preferably 0.6 wt.-% to 1 wt.-% glass fibers based on the weight of the gypsum in the board. The glass fibers give the board more overall strength.

Any, some or all of the gypsum boards of layer S1 LG and/or S2LG can further comprise 0.1 wt.-% to 3 wt.-% starch, preferably 0.1 wt.-% to 1 wt.-% starch based on the weight of the gypsum present in the board. The starch can be e. g. native starch, modified starch, pre-gelatinized starch, cold water-soluble starch, migrating starch, non-migrating starch. In many cases, the starch improves the bonding of the liner to the gypsum core and/or improves the overall strength of the board.

Preferably, any, some or all of the gypsum boards of layer S1 LG and/or S2LG comprise 2 to 4 wt.-% polyvinyl acetate based on its solids content, relative to the gypsum present in the board. Polyvinyl acetate in the disclosed amount imparts toughness and/or more strength.

Gypsum boards comprising a combination of polyvinyl acetate, glass fibers and starch in the disclosed amounts appear to be particularly advantageous.

Advantageously, any, some or all of the gypsum fiberboards of S1 LF and/or S2LF each have two tongue-shaped edges and two groove-shaped edges such that adjacent gypsum fiberboards can be joined by tongue-and-groove joints, preferably all of the gypsum fiberboards of S1 LF and/or S2LF have two adjacent tongue-shaped edges and two adjacent groove-shaped edges. A tongue-shaped edge of a gypsum fiberboard can be joined to a groove-shaped edge of another gypsum fiberboard to form a tongue-and- groove joint. In embodiments, wherein the layer S1 LF or the layer S2LF comprise at least two fiberboards, these tongue-and-groove joints offer the wall assembly more stability than standard joints or joints that require and adhesive, particularly the horizontal joints of a wall assembly. Tongue-and-groove joints offer more flexibility in the placement of the vertical framing members, because building boards with tongue-and-groove joints do not need to be attached to the sub-structure along the edge of the board. In fact, preferably, the attachment means do not attach the gypsum fiberboards with tongue-and-groove edges near the edges, wherein “near” denotes a distance less than 40 mm from the edge. Particularly with tongue-and-groove joints, no adhesive is required for joining gypsum fiberboard of one layer to an adjacent layer.

Preferably, the layer S1 LF comprises at least two gypsum fiberboards, and any, some or all of the gypsum fiberboards of layer S1 LF are joined to adjacent gypsum fiberboards of the same layer without an adhesive and/or the layer S2LF comprises at least two gypsum fiberboards, and all of the gypsum fiberboards of layer S2LF are joined to adjacent gypsum fiberboards of the same layer without an adhesive. Omitting an adhesive in a joint, reduces the assembly steps and thus reduces the cost of labor.

The framing members can be made of e.g. steel or timber, preferably steel, more preferably steel of at least 0.8 mm gauge, most preferably steel of at least 1 .0 mm gauge. Reinforcement framing members, particularly reinforcement studs, are made of steel of at least gauge 0.8 mm. They are typically used for load-bearing walls or unusually high non- loadbearing walls. If gypsum fiberboards or gypsum boards are to be nailed to the substructure, reinforcement framing members are necessary.

Preferably, the layer S1 LF and/or the layer S2LF each have a total thickness of at least 50 mm. A total thickness of at least 50 mm improves the bullet resistance to at least FB6 according to EN 1522:1998. For example, two 28 mm thick sub-layers can be used to achieve a total thickness of at least 50 mm. Non-mirror-symmetrical wall assemblies are most effective, if the first side, i.e. the side with the thicker layers, face the impact, strike, projectile or assault.

Preferably, the layer S1 LG and/or S2LG each has a total thickness of at least 24 mm. For example, two 12.5 mm thick sub-layers can be used to achieve a total thickness of at least 24 mm. A total thickness of at least 24 mm improves the bullet resistance to at least FB5 according to EN 1522:1998. Non-mirror-symmetrical wall assemblies are most effective, if the first side, i.e. the side with the thicker layers, face the impact, strike, projectile or assault.

In advantageous embodiments, one, more than one or all of the following preferred aspects of the invention are realized. Such embodiments may also realize one or more of the features disclosed elsewhere in this application.

Preferably, the layers S1 LF and/or the layer S2LF have a total thickness of at least 50 mm each and the layer S1 LG has a total thickness of at least 24 mm. A total thickness of at least 24 mm gypsum board can improve the bullet resistance to beyond FB6 according to EN 1522:1998.

Preferably, the layers S1 LF and S1 LG are in direct contact with one another. This means that no other material, except the attachment means or air, separate the layers S1 LF and S1 LG.

Preferably, the first side of the wall and the second side of the wall are mirror symmetrical. For example, if the layer S1 LF is attached directly to the sub-structure, then the layer S2LF is attached directly to the sub-structure. If the layer S1 LF comprises two sub-layers, then the layer S2LF comprises two sub-layers. Also, to achieve the specified symmetry, at least one layer S2LG of at least one gypsum board, wherein all of the gypsum boards of layer S2LG comprise 1 wt.% to 5 wt.% polyvinyl acetate based on its solids content, relative to the weight of the gypsum a layer S2LG must be present. If S1 LG is an outermost layer, then the layer S2LG is an outermost layer. In terms of this invention “outermost” refers to the layer of building board, either gypsum board or gypsum fiberboard, that is farthest from the sub-structure and/or faces the interior of a room. Generally, this will be the layer of building board of one side, either gypsum board or gypsum fiberboard, that was attached last. Also, S1 LF and S2LF will be identical in thickness and/or in composition. The same holds true for S1 LG and S2LG. If a second layer of gypsum fiberboard S1 LF2 is present on the first side, then a second layer of gypsum fiberboard S2LF2 will be present on the second side. If a second layer of gypsum board S1 LG2 is present on the first side, then a second layer of gypsum board S2LG2 will be present on the second side. A mirror symmetrical wall assembly has the advantage that it has the same projectile resistance on both sides of the wall assembly.

Preferably, any, some or all of the gypsum fiberboards and all of the gypsum boards are attached to the sub-structure or to an underlying building board (gypsum fiberboard or gypsum board) by an attachment means. The attachment means can be e.g. screws, staples, nails or adhesive. Whereas a gypsum board is typically screwed to a substructure or to an underlying building board, gypsum fiberboards typically require predrilling in order to be screwed. In the past, adhesives have been used to attach gypsum fiberboards either to the sub-structure or to underlying building boards. This has the advantage that no joint filler is needed to cover e.g. screw heads. In this invention, the preferred attachment means are nails, more preferred, the attachment means are ballistic nails/nail gun drivable nails. Attachment via nails is fast and equally reliable compared to screws. Ballistic nails are nails that are discharged from a nail gun (e.g. pneumatic or powder-actuated tools). Especially (magazine-fed) ballistic nails are an extremely efficient attachment means. Most preferably, the ballistic nails are made of galvanized carbon steel and/or are fluted and/or have a diamond coated tip or a ballistic tip. A ballistic tip is somewhat rounded like a bullet. (Ballistic) nails with a head or without a head are equally effective for attaching a layer of fiberboard, such as S1 LF or S2LF and/or or for attaching a layer of gypsum board, such as S2LG or S2LG. Particularly preferably, (ballistic) nails with a head can be used for attaching a layer of fiberboard, such as S1 LF or S2LF and/or (ballistic) nails without a head can be used for attaching a layer of gypsum board, such as S2LG or S2LG. The length of the nail shaft can vary from 20 mm to 60 mm. Typically, the shorter lengths, such as 25 mm, are used for gypsum board. The longer lengths, such as 35 mm to 55 mm, are generally used for gypsum fiberboard, whereby an attachment to the sub-structure requires longer nails than attaching to another board. The diameter of the nail shaft can vary from 1 .5 mm to 3.0 mm. Typically, the smaller diameters, such as 1.8 mm, are used for gypsum board. The larger diameters, such as 2.2 mm to 2.8 mm, are generally used for gypsum fiberboard. By using nails without a head, less joint filler is needed to cover the nails. This is particularly advantageous for the outermost layers. Also, by not attaching all layers to the sub-structure, the load can be distributed and/or joints between building boards of adjacent layers can be staggered i.e. not overlapping. Not overlapping means that vertical joints of one layer will not overlap with vertical joints of an adjacent layer. However, depending on the arrangement, vertical joints between building boards of one layer crossing horizontal joints between building boards of an adjacent layer are not considered to be overlapping.

Preferably, the attachment means of the wall assembly do not comprise an adhesive. In another preferred embodiment, any, some or all of the gypsum fiberboards of S1 LF and/or S2LF are not pre-drilled.

Preferably, there are joints between the building boards of one layer and the joints do not overlap with the joints of an adjacent (e.g. underlying or overlying) layer. One layer of building boards can be the layer S1 LF, the layer S2LF, the layer S1 LG, the layer S2LG or further layers. The joints are formed between adjacent building boards of the same layer. Joints are generally considered weak spots. By staggering the joints of adjacent layers a higher overall strength of the wall assembly can be achieved.

Preferably, the inventive wall assembly in all embodiments does not comprise a metal sheet. Omitting a metal sheet saves cost and simplifies the assembly of the wall.

Preferably, both the layers S1 LF and S2LF are in direct contact with the sub-structure, preferably with a stud. Direct contact in relation to the sub-structure means that both layers S1 LF and S2LF are attached to the sub-structure with attachment means. More preferably, they are not separated by another material along the contacting surface, whereby the only material present along the contacting surface would be the attachment means or a thin layer of air, which can be construction related. Attaching S1 LF and S2LF directly to the sub-structure yields a more stable wall assembly.

Preferably, the layer S1 LG and/or the layer S2LG is an outermost layer. The gypsum board of the layer S1 LG or the layer S2LG not only provides the technical features for an improved bullet resistance, but it also provides a better basis for decorative coats such as a layer of plaster or wallpaper compared to, e.g. a gypsum fiberboard. If the gypsum board is used as an outermost layer, it serves this additional advantage.

Preferably, any, some or all of the gypsum fiberboards of both layers S1 LF and S2LF have a thickness of 10 mm to 40 mm, preferably 15 mm to 35 mm, most preferably 24 to 30 mm and/or a density greater than 1200 kg/m³ and less than 2000 kg/m³, preferably greater than 1400 kg/m³ and less than 1800 kg/m³, further preferably greater than 1500 kg/m³ and less than 1700 kg/m³. Gypsum fiberboards dimensioned 1200 mm by 600 mm are particularly useful. Typically, the fibers of the gypsum fiberboard are cellulose-based and/or originate from paper pulp.

Preferably, any, some or all of the gypsum fiberboards comprise fibers with at least one predominant orientation, more preferably with at least two predominant orientations at right angles to one another, most preferably the predominant orientation further comprises an orientation parallel to the main surfaces of the gypsum fiberboard. A predominant orientation is a characteristic feature of a particular production process, which yields gypsum fiberboards with a higher flexural strength compared gypsum fiberboards comprising fibers without a predominant orientation from a different production process. During this particular type of production, the fibers of the gypsum fiberboard are aligned in the machine direction. This alignment or predominant orientation influences the flexural strength and breaking load of the boards. To strengthen the boards further, e.g. further increase their flexural strength, the gypsum fiberboards can comprise at least two layers joined transversally (by pressure), such the fibers of one layer are essentially at right angles to the fibers of the adjacent fiberboard layer. These gypsum fiberboards are also more resilient compared to gypsum fiberboards that comprise fibers with a random alignment or without a particular orientation. The fibers can have a mean length of 1 mm to 5 mm, preferably 1 mm to 4 mm, further preferably 1 mm to 3 mm. Preferably, the fibers have a mean diameter of 15 pm to 50 pm. The building panels can have a fiber content of 5 wt.-% to 25 wt.-% relative to the weight of the gypsum.

Preferably, the assembly meets the classification of at least FB4 according to EN1522:1998, preferably at least FB5, more preferably at least FB6 and most preferably at least FB7.

Preferably, the vertical framing members of the inventive wall assembly are spaced 400 to 650 mm apart. These measurements refer to on-center measurements, wherein the median line of a stud (i.e. the flange of a metal stud) or side (timber stud) is distanced e.g. 450 mm, 500 mm, 600 mm or 625 mm to the median line of an adjacent stud. More preferably, the framing members are spaced 445 mm to 630 mm apart.

A preferred framing member is a reinforcement framing member. The reinforcement framing member preferably has a steel gauge of 1 .0 mm to 1 .5 mm. Its web can have a width of 45 mm, 70 mm, 95 mm, 120 mm, 145 mm or 160 mm wide. A width of 60 mm to 80 mm is particularly preferred. Its two flanges can have a different width, e.g. 42 mm on one side and 46 mm on the other side.

The inventive wall assembly in all embodiments can be a partition.

Another aspect of the invention concerns the method to build a wall assembly comprising a sub-structure made of framing members with building boards attached to two opposing sides of the sub-structure to form a first side of a wall and a second side of a wall, comprising the following steps: positioning at least two framing members - attaching at least one layer S1 LF of gypsum fiberboard with a total thickness of 25 mm on the first side,

- attaching at least one layer S1 LG of gypsum board on the first side, wherein the gypsum board comprises 1 wt.-% to 5 wt.-% polyvinyl acetate based on its solids content, relative to the weight of the gypsum

- attaching at least one layer S2LF of gypsum fiberboard with a total thickness of at least 25 mm on the second side and

- providing a cavity between the two opposing sides, wherein the cavity has a thickness of at least 40 mm and is filled with air or an insulation material.

Preferably, the inventive wall assembly is built with this method.

This method can further be applied to any of the embodiments described for the wall assembly.

A further aspect of the invention concerns the use of gypsum boards in a wall assembly, wherein the gypsum boards comprise 1 wt.-% to 5 wt.-% polyvinyl acetate based on its solids content, relative to the weight of the gypsum in the board, to achieve a bullet resistance of the wall assembly, preferably the bullet resistance meets at least the classification of FB6 according to EN1522:1998.

Preferably, the use of the gypsum boards yields the inventive wall assembly or a wall assembly built by the inventive method.

Preferably, the use further encompasses any of the advantageous embodiments disclosed for the wall assembly.

The invention is further exemplified with the following list of favorable embodiments (FE):

Embodiment FE 1 : A wall assembly comprising a sub-structure made of framing members with building boards attached to two opposing sides of the sub-structure to form a first side of a wall and a second side of a wall, wherein

- the first side of the wall comprises at least one layer S1 LF of at least one gypsum fiberboard, wherein the layer S1 LF has a total thickness of at least 25 mm,

- the first side of the wall further comprises at least one layer S1 LG of at least one gypsum board, wherein all of the gypsum boards of layer S1 LG comprise 1 -5 wt.% polyvinyl acetate based on its solids content, relative to the weight of the gypsum and - the second side of the wall comprises at least one layer S2LF of at least one gypsum fiberboard, wherein the at least one layer S2LF has a thickness of at least 25 mm and

Embodiment FE 2: A wall assembly according to the embodiment FE 1 , wherein the second side further comprises at least one layer S2LG of at least one gypsum board, wherein any, some or all of the gypsum boards of layer S2LG comprise 1 wt.-% to 5 wt.-% polyvinyl acetate based on its solids content, relative to the weight of the gypsum

Embodiment FE 3: A wall assembly according to any of the embodiments FE 1 or FE 2, wherein any, some or all of the gypsum boards of the layer S1 LG and/or all of the gypsum boards of the layer S2LG further comprise glass fibers, preferably 0.5 wt.-% to 2 wt.-% glass fibers, more preferably 0.6 wt.-% to 1 wt.-% glass fibers relative to the weight of the gypsum in the board.

Embodiment FE 4: A wall assembly according to any of the embodiments FE 1 , FE 2 or FE 3, wherein any, some or all of the gypsum boards of the layer S1 LG and/or all of the gypsum boards of the layer S2LG further comprise 0.1 wt.-% to 3 wt.-% starch, preferably 0.1 wt.-% to 1 wt.-% starch based on the weight of the gypsum present in the board.

Embodiment FE 5: A wall assembly according any of the embodiments FE 1 , FE 2, FE 3 or FE 4, wherein any, some or all of the gypsum boards of the layer S1 LG and/or all of the gypsum boards of the layer S2LG comprise 2 wt.-% to 4 wt.-% polyvinyl acetate based on its solids content, relative to the gypsum.

Embodiment FE 6: The wall assembly according to any of the embodiments FE 1 , FE 2, FE 3, FE 4 or FE 5, wherein any, some or all of the gypsum fiberboards of both layers S1 LF and S2LF have two tongue-shaped edges and two groove-shaped edges such that adjacent gypsum fiberboards can be joined by tongue-and-groove joints, preferably all of the gypsum fiberboard of layers S1 LF and S2LF has two adjacent tongue-shaped edges and two adjacent groove-shaped edges.

Embodiment FE 7: The wall assembly according to any of the embodiments FE 1 , FE 2, FE 3, FE 4, FE 5 or FE 6, wherein layer S1 LF comprises at least two gypsum fiberboards, and all of the gypsum fiberboards of layer S1 LF is joined to adjacent gypsum fiberboards of the same layer without an adhesive and/or layer S2LF comprises at least two gypsum fiberboards, and any of the gypsum fiberboards of layer S2LF is joined to adjacent gypsum fiberboards of the same layer without an adhesive. Embodiment FE 8: The wall assembly according to any of the embodiments FE 1 , FE 2, FE 3, FE 4, FE 5, FE 6 or FE 7, wherein the framing members are made of steel or timber, preferably steel, more preferably steel of at least 0.8 mm gauge, most preferably steel of at least 1 .0 mm gauge.

Embodiment FE 9: The wall assembly according to any of the embodiments FE 1 , FE 2, FE 3, FE 4, FE 5, FE 6, FE 7 or FE 8, wherein the layer S1 LF and/or the layer S2LF have a total thickness of at least 50 mm.

Embodiment FE 10: The wall assembly according to any of the embodiments FE 1 , FE 2, FE 3, FE 4, FE 5, FE 6, FE 7, FE 8 or FE 9, wherein the layer S1 LG and/or the layer S2LG have a total thickness of at least 24 mm.

Embodiment FE 11 : The wall assembly according to any of the embodiments FE 9 or FE 10, wherein both layers S1 LF and S2LF have a total thickness of at least 50 mm and the layer S1 LG has a total thickness of at least 24 mm.

Embodiment FE 12: The wall assembly according to any of the embodiments FE 1 , FE 2, FE 3, FE 4, FE 5, FE 6, FE 7, FE 8, FE 9, FE 10 or FE 11 , wherein the layers S1 LF and S1 LG are in direct contact with one another.

Embodiment 13: The wall assembly according to any of the embodiments FE 1 , FE 2, FE 3, FE 4, FE 5, FE 6, FE 7, FE 8, FE 9, FE 10, FE 11 or FE 12, wherein the first side and the second side of the wall structure are mirror symmetrical.

Embodiment 14: The wall assembly according to any of the embodiments FE 1 , FE 2, FE 3, FE 4, FE 5, FE 6, FE 7, FE 8, FE 9, FE 10, FE 11 , FE 12 or FE 13, wherein any, some or all of the gypsum fiberboards and all of the gypsum boards are attached to the sub-structure or to an underlying building board by an attachment means, preferably the attachment means are nails, more preferably the attachment means are ballistic nails, most preferably the ballistic nails are made of galvanized carbon steel and/or are fluted and/or have a ballistic tip.

Embodiment FE 15: The wall assembly according to the embodiment FE 14, wherein the attachment means do not comprise an adhesive.

Embodiment FE 16: The wall assembly according to any of the embodiments FE 1 , FE 2, FE 3, FE 4, FE 5, FE 6, FE 7, FE 8, FE 9, FE 10, FE 11 , FE 12, FE 13, FE 14 or FE 15, wherein all of the gypsum fiberboards of S1 LF and/or S2LF are not pre-drilled.

Embodiment FE 17: The wall assembly according to any of the embodiments FE 1 , FE 2, FE 3, FE 4, FE 5, FE 6, FE 7, FE 8, FE 9, FE 10, FE 11 , FE 12, FE 13, FE 14, FE 15 or FE 16, wherein there are joints between the building boards of one layer and the joints do not overlap with the joints of an adjacent layer.

Embodiment FE 18: The wall assembly according to any of the embodiments FE 1 , FE 2, FE 3, FE 4, FE 5, FE 6, FE 7, FE 8, FE 9, FE 10, FE 11 , FE 12, FE 13, FE 14, FE 15,

FE 16 or FE 17, wherein the wall assembly does not comprise at metal sheet.

Embodiment FE 19: The wall assembly according to any of the embodiments FE 1 , FE 2, FE 3, FE 4, FE 5, FE 6, FE 7, FE 8, FE 9, FE 10, FE 11 , FE 12, FE 13, FE 14, FE 15,

FE 16, FE 17 or FE 18, wherein both layers S1 LF and S2LF are in direct contact with the sub-structure, preferably with a stud.

Embodiment FE 20: The wall assembly according to any of the embodiments FE 1 , FE 2, FE 3, FE 4, FE 5, FE 6, FE 7, FE 8, FE 9, FE 10, FE 11 , FE 12, FE 13, FE 14, FE 15, FE 16, FE 17, FE 18 or FE 19, wherein the layer S1 LG and/or the layer S2LG is an outermost layer.

Embodiment FE 21 : The wall assembly according to any of the embodiments FE 1 , FE 2, FE 3, FE 4, FE 5, FE 6, FE 7, FE 8, FE 9, FE 10, FE 11 , FE 12, FE 13, FE 14, FE 15, FE 16, FE 17, FE 18, FE 19 or FE 20, wherein any of the gypsum fiberboards of both layers S1 LF and S2LF have a thickness of 10 mm to 40 mm, preferably 15 mm to 35 mm, most preferably 24 to 30 mm and/or a density greater than 1200 kg/m3 and less than 2000 kg/m3, preferably greater than 1400 kg/m3 and less than 1800 kg/m3, further preferably greater than 1500 kg/m3 and less than 1700 kg/m3.

Embodiment FE 22: The wall assembly according to any of the embodiments FE 1 , FE 2, FE 3, FE 4, FE 5, FE 6, FE 7, FE 8, FE 9, FE 10, FE 11 , FE 12, FE 13, FE 14, FE 15, FE 16, FE 17, FE 18, FE 19, FE 20 or FE 21 , wherein all of the gypsum fiberboards of both layers S1 LF and S2LF comprise fibers with at least one predominant orientation, preferably with at least two predominant orientations at right angles to one another, more preferably the predominant orientation further comprises an orientation parallel to the main surfaces of the gypsum fiberboard.

Embodiment FE 23: The wall assembly according to any of the embodiments FE 1 , FE 2, FE 3, FE 4, FE 5, FE 6, FE 7, FE 8, FE 9, FE 10, FE 11 , FE 12, FE 13, FE 14, FE 15, FE 16, FE 17, FE 18, FE 19, FE 20, FE 21 or FE 22, wherein the assembly meets the classification of at least FB4 according to EN1522:1998, preferably at least FB5, more preferably at least FB6 and most preferably at least FB7.

Embodiment FE 24: Method to build a wall assembly comprising a sub-structure made of framing members with building boards attached to two opposing sides of the sub-structure to form a first side of a wall and a second side of a wall, especially a wall assembly according to any of the embodiments FE 1 , FE 2, FE 3, FE 4, FE 5, FE 6, FE 7, FE 8, FE 9, FE 10, FE 11 , FE 12, FE 13, FE 14, FE 15, FE 16, FE 17, FE 18, FE 19, FE 20, FE 21 , FE 22 or FE 23, comprising the following steps:

- positioning at least two framing members

- attaching at least one layer S1 LF of gypsum fiberboard with a total thickness of at least 25 mm on the first side,

- attaching at least one layer S1 LG of gypsum board on the first side, wherein the gypsum board comprises 1-5 wt.% polyvinyl acetate

Embodiment 25: Use of gypsum boards in a wall assembly, especially in a wall assembly according to any of the embodiments FE 1 , FE 2, FE 3, FE 4, FE 5, FE 6, FE 7, FE 8, FE 9, FE 10, FE 11 , FE 12, FE 13, FE 14, FE 15, FE 16, FE 17, FE 18, FE 19, FE 20, FE 21 , FE 22 or FE 23 or in a wall assembly built according to the embodiment FE 24, wherein the gypsum boards comprise 1-5 wt.% polyvinyl acetate based on its solids content, relative to the weight of the gypsum in the board, to achieve a bullet resistance of the wall assembly, preferably the bullet resistance meets at least the classification of FB6 according to EN1522:1998.

The invention is explained further in the figures. However, it is not intended to limit the scope of the invention and the general teaching by the chosen embodiments in the figures.

Fig. 1 : Schematic representation of a vertical cross-section of a wall assembly according to the invention with S1 LF, S1 LG and S2LF.

Fig. 2: Schematic representation of an alternative embodiment of a wall assembly according to the invention with S1 LF, S1 LG, S2LF and S2LG.

Fig. 3 : Schematic representation of an alternative embodiment of a wall assembly according to the invention with S1 LF, S1 LG, and S2LF.

Fig. 4: Schematic representation of an alternative embodiment of a wall assembly according to the invention with S1 LF, S1 LG, S2LF and S2LG.

Fig. 5: Schematic representation of an alternative embodiment of a wall assembly according to the invention with S1 LF, S1 LG, S2LF and S2LG. Fig. 6: Schematic representation of an alternative embodiment of a wall assembly according to the invention with S1 LF, S1 LG, S2LF and S2LG.

Fig. 7: Schematic representation of an alternative embodiment of a wall assembly according to the invention with S1 LF, S1 LG, S1 LF2, S1 LG2, S2LF, S2LG, S2LF2 and S2LG2.

Reference number:

1 wall assembly

2 vertical framing member

3 attachment means

4 cavity

5 S1 LF (layer of gypsum fiberboard on the first side)

6 S1 LG (layer of gypsum board on the first side)

7 S2LF (layer of gypsum fiberboard on the second side)

8 S2LG (layer of gypsum board on the second side)

9 S1 LF2 (second layer of gypsum fiberboard on the first side)

10 S1 LG2 (second layer of gypsum board on the first side)

11 S2LF2 (second layer of gypsum fiberboard on the second side)

12 S2LG2 (second layer of gypsum board on the second side)

Fig. 1 depicts an embodiment with both S1 LF and S2LF as innermost layers, which are attached directly to the vertical framing member, e.g. a metal or a timber stud, preferably a C-shaped or U-shaped metal stud. Here, one layer of 28 mm thick gypsum fiberboards makes up S1 LF. Likewise, one layer of 28 mm thick gypsum fiberboards makes up S2LF. Alternatively, two sub-layers of 12.5 mm thick gypsum fiberboards that are in direct contact one another yield a total thickness of 50 mm and could replace the layer of 28 mm thick gypsum fiberboards. If the layer S1 LF consists of two sub-layers of gypsum fiberboards, then the innermost sub-layer is preferably attached directly to the vertical framing member by attachment means. Subsequent sub-layers or layers are preferably attached to an underlying layer or sub-layer by attachment means. S1 LG can be one layer of gypsum boards with a thickness of e.g. 12.5 or 15 mm. In this embodiment, S1 LG is an outermost layer, whereas S2LF is both the outermost and the innermost layer. The attachment means are depicted as nails. In the figure, nails without a head are used to attach the gypsum boards. However, this embodiment is not limited to nails with or without head. Nails can be substituted by e.g. screws, staples or adhesive as an attachment means.

Fig. 2 depicts a mirror symmetrical embodiment, with S1 LF and S2LF as innermost layers and S1 LG and S2LG as outermost layers. Here, one layer of 28 mm thick gypsum fiberboards makes up S1 LF. Likewise, one layer of 28 mm thick gypsum fiberboards makes up S2LF. S1 LF and S2LF can be attached directly to the vertical framing member by attachment means. Analogous to the embodiment of Fig. 1 , two sub-layers of 12.5 mm thick gypsum fiberboards could make up S1 LF and/or S2LF. S1 LG and S2LG are attached to the underlying layers S1 LF and S2LF, respectively. The vertical framing member can be e.g. a metal or a timber stud, preferably a C-shaped or U-shaped metal stud. The attachment means are depicted as nails. In the figure, nails without a head are used to attach the gypsum boards. However, this embodiment is not limited to nails with or without head. Nails can be substituted by e.g. screws, staples or adhesive as an attachment means.

Fig. 3 exemplifies an embodiment similar to the one depicted in Fig. 1. Here, S1 LF is made up of two sub-layers of gypsum fiberboard each of the two sub-layers having a thickness of 25 mm or 28 mm. The innermost sub-layer or layer is preferably attached directly to the vertical framing member, e.g. a metal or a timber stud, preferably a C- shaped or U-shaped metal stud, by attachment means. Subsequent sub-layers or layers are preferably attached to an underlying layer by attachment means. The attachment means are depicted as nails. In the figure, nails without a head are used to attach the gypsum boards. However, this embodiment is not limited to nails with or without head. Nails can be substituted by e.g. screws, staples or adhesive as an attachment means.

Fig. 4 shows a non-symmetrical wall assembly with S1 LF and S1 LG on the first side and S2LF and S2LG on the second side. S1 LF consists of two sub-layers of gypsum fiberboard, whereas S2LF consists of only one layer of gypsum fiberboard. The gypsum fiberboards in these layers or sub-layers can have a thickness of e.g. 25 mm or 28 mm. The innermost sub-layer or layer is preferably attached directly to the vertical framing member, e.g. a metal or a timber stud, preferably a C-shaped or U-shaped metal stud, by attachment means. Subsequent sub-layers or layers are preferably attached to an underlying layer by attachment means. The attachment means are depicted as nails. In the figure, nails without a head are used to attach the gypsum boards. However, this embodiment is not limited to nails with or without head. Nails can be substituted by e.g. screws, staples or adhesive as an attachment means. Fig. 5 depicts a mirror-symmetrical wall assembly with S1 LF and S1 LG on the first side and S2LF and S2LG on the second side. S1 LF and S2LF have the same thickness. Similarly, S1 LG and S2LG have the same thickness. Both S1 LF and S2LF consist of two sub-layers of gypsum fiberboard. The gypsum fiberboards in these sub-layers can have a thickness of e.g. 25 mm or 28 mm. The innermost sub-layer or layer is preferably attached directly to the vertical framing member, e.g. a metal or a timber stud, preferably a C- shaped or U-shaped metal stud, by attachment means. Subsequent sub-layers or layers are preferably attached to an underlying layer by attachment means. The attachment means are depicted as nails. In the figure, nails without a head are used to attach the gypsum boards. However, this embodiment is not limited to nails with or without head. Nails can be substituted by e.g. screws, staples or adhesive as an attachment means.

Fig. 6 shows an embodiment similar to the embodiment of Fig. 1. Here, both S1 LF and S2LF consist of two sub-layers of gypsum fiberboards. The gypsum fiberboards in these sub-layers can have a thickness of e.g. 25 mm or 28 mm. S1 LG and S2LG, too, consist of two sub-layers. The sub-layers of S1 LG and S2LG can have a thickness of e.g. 12.5 mm or 15 mm. The innermost sub-layer or layer is preferably attached directly to the vertical framing member, e.g. metal or timber stud, preferably a C-shaped or U-shaped metal stud, by attachment means. Subsequent sub-layers or layers are preferably attached to an underlying layer by attachment means. The attachment means are depicted as nails. In the figure, nails without a head are used to attach the gypsum boards. However, this embodiment is not limited to nails with or without head. Nails can be substituted by e.g. screws, staples or adhesive as an attachment means.

Fig. 7 depicts and embodiment with S1 LF, S1 LG, S1 LF2, S1 LG2, S2LF, S2LG, S2LF2 and S2LG2. S1 LF, S1 LF2, S2LF and S2LF2 can have a thickness of e.g. 25 mm or 28 mm. S1 LG, S1 LG2, S2LG and S2LG2 can have a thickness of e.g. 12.5 mm or 15 mm. The innermost sub-layer or layer is preferably attached directly to the vertical framing member, e.g. a metal or a timber stud, preferably a C-shaped or U-shaped metal stud by attachment means. Subsequent sub-layers or layers are preferably attached to an underlying layer by attachment means. The attachment means are depicted as nails. In the figure, nails without a head are used to attach the gypsum boards. However, this embodiment is not limited to nails with or without head. Nails can be substituted by e.g. screws, staples or adhesive as an attachment means.

Examples

Again, it is not intended to unnecessarily restrict the invention. Where the effect of special features is shown, actual chosen parameters of the samples - like dimensions or components - are not intended to limit the invention to the respective embodiments, where this is not necessary.

The gypsum fiberboards used in all examples were gypsum fiberboards known in the art with a gypsum content of 90 wt.-% to 95 wt.%, in this particular case about 93 wt.-% based on the weight of the board and a cellulose fiber content of 8 wt. % to 11 wt.-%, in this particular case about 10 wt.-% based on the gypsum in the board. The gypsum fiberboards had a density of 1500 ± 50 kg/m³. The gypsum boards in all examples were gypsum boards known in the art with a gypsum content of 90 wt.-% to 97 wt.-%, in this particular case about 95 wt.-% based on the weight of the board and a density of 960 ± 20 kg/m³. As is common in the art, they had paper liners of 200 g/m² and 180 g/m² and also contained 0.4 wt.-% to 1.0 wt.-% glass fibers and 0.1 wt.-% to 0.4 wt.-% starch, in this particular case about 0.6 wt.-% glass fibers and about 0.2 wt.-% starch, all based on the gypsum in the board. Additionally, they comprised 2.0 wt.% to 3.5 wt.-% polyvinyl acetate, in this particular case 2.9 wt.-% polyvinyl acetate based on its solids content, relative to the weight of the gypsum in the board. The reinforcement studs that were used were C-shaped and had a steel gauge of 1.00 mm, with web of 70 mm, one flange of 42 mm, and the other flange of 46 mm, giving the cavity a thickness of about 70 mm. The reinforcement rails were U-shaped and had steel gauge of 1.00 mm and a flange of 45 mm, however any flange from 40 mm to 65 mm is suitable, such as e.g. 52 mm or 57 mm. In the test, the studs were distanced 500 mm from one another and placed in a wooden frame. Bullets according to EN 1522:1998 were used. Staggered placement of boards ensured that the joints between boards of one layer never overlapped with the joints between boards of the next layer. All tests were carried out according to EN 1523:1998.

Example 1

The following wall assembly passed the test for bullet resistance class FB4 according to EN 1522:1998: 28 mm gypsum fiberboards were attached to both flanges of a reinforcement stud (steel gauge 1 mm) via ballistic nails (galvanized carbon steel, 50 mm shaft, 2.5 mm to 2.8 mm diameter). 12.5 mm gypsum boards containing polyvinyl acetate were attached to the gypsum fiberboards via ballistic nails (galvanized carbon steel, 25 mm shaft, 1.8 mm diameter, without head). All nails were distanced 10 cm from one another in the vertical dimension. Three studs with a length of 1.0 m were positioned in reinforcement rails (steel gauge 1 mm) and spaced apart 50 cm. The rails each had a length of 1 .0 m. The gypsum fiberboards were cut to 410 mm x 1000 mm and 590 mm x 1000 mm and were joined by tongue-and-groove joints to form an area of 1 .0 m². This was done on both sides of the wall assembly. The gypsum boards comprising polyvinyl acetate had a size of 590 mm x 300 mm, 590 mm x 700 mm, 410 mm x 300 mm, 410 mm x 700 mm on one side, the other side 410 mm x 100 mm, 410 mm x 900 mm, 590 mm x 100 mm and 590 mm x 900 mm. The boards were joined to form a total area of 1 .0 m² on each side. The dimensions of the building boards as well as the distance between the studs and/or nails were chosen to suit the test requirements. They do not reflect typical building board dimensions. Joints crossed one another, but did not overlap entirely.

Example 2

The following wall assembly, comprising different arrangements on the two sides of the wall, passed the test for bullet resistance class FB5 according to EN 1522:1998 for shots fired towards both sides: on one side, 28 mm thick gypsum fiberboards were attached to both flanges of a reinforcement stud (galvanized steel gauge 1 .0 mm) via ballistic nails (galvanized carbon steel, 50 mm shaft, 2.5 mm to 2.8 mm diameter). 28 mm thick gypsum fiberboards were attached to the underlying gypsum fiberboards via ballistic nails (galvanized carbon steel, 40 mm shaft, 2.8 mm diameter). 12.5 mm thick gypsum boards containing polyvinyl acetate were attached to the outermost gypsum fiberboards via ballistic nails (galvanized carbon steel, 25 mm shaft, 1.8 mm diameter, without head). On the opposing side, 28 mm gypsum fiberboards were attached to the flange of the reinforcement stud (steel gauge 1.0 mm) via ballistic nails (galvanized carbon steel, 50 mm shaft, 2.5 mm to 2.8 mm diameter). 12.5 mm gypsum boards containing polyvinyl acetate were attached to the gypsum fiberboards via ballistic nails (galvanized carbon steel, 25 mm shaft, 1 .8 mm diameter, without head). A second layer of 12.5 mm gypsum boards comprising polyvinyl acetate was attached to the underlying layer of gypsum boards comprising polyvinyl acetate via ballistic nails (galvanized carbon steel, 25 mm shaft, 1 .8 mm diameter, without head). The nails were distanced 10 cm from one another in the vertical dimension. Three studs with a length of 1.0 m were positioned in reinforcement rails (steel gauge 1 mm) and spaced apart 50 cm. The rails each had a length of 1.0 m. The gypsum fiberboards were cut to the following sizes: 540 mm x 1000 mm, 460 mm x 1000 mm (first sub-layer on first side), two boards of 500 mm x 1000 mm (second sub-layer on first side) and 590 mm x 1000 mm, 410 mm x 1000 mm (second side). The boards of one sub-layer (first side) or layer (second side) were joined by tongue-and-groove joints to form an area of 1 .0 m². The joints between fiberboards ran horizontally. The boards were arranged such that none of the joints overlapped, regardless whether they were located on the first or the second side. The gypsum boards comprising polyvinyl acetate had a size of 300 mm x 1000 mm, 700 mm x 1000 mm, 200 mm x 1000 mm and 800 mm x 1000 mm in each layer or sub-layer. They were joined to form a total area of 1 .0 m². They were attached to the underlying second sub-layer of gypsum fiberboards. The joints between the gypsum boards ran vertically. The boards were arranged such that none of the joints overlapped, regardless whether they were located on the first or the second side. Three shots were fired towards the first side with two sub-layers of 28 mm thick gypsum fiberboard and one layer of 12.5 thick gypsum board. The dimensions of the building boards as well as the distance between the studs and/or nails were chosen to suit the test requirements. They do not reflect typical building board dimensions.

Example 3

The following wall assembly passed the test for bullet resistance class FB6 according to EN 1522:1998: 28 mm gypsum fiberboards were attached to both flanges of a reinforcement stud (steel gauge 1 mm) via ballistic nails (galvanized carbon steel, 50 mm shaft, 2.5 mm to 2.8 mm diameter). 28 mm gypsum fiberboards were attached to the underlying gypsum fiberboards via ballistic nails (galvanized carbon steel, 40 mm shaft, 2.5 mm to 2.8 mm diameter). 12.5 mm gypsum boards polyvinyl acetate were attached to the outermost gypsum fiberboards via ballistic nails (galvanized carbon steel, 25 mm shaft, 1 .8 mm diameter, without head). The nails were distanced 10 cm from one another in the vertical dimension. Three studs with a length of 1.0 m were positioned in reinforcement rails (steel gauge 1 mm) and spaced apart 50 cm. The rails each had a length of 1.0 m. The gypsum fiberboards were cut to: 460 mm x 1000 mm, 540 mm x 1000 mm for the first sub-layer of the first side and two boards of 500 mm x 1000 mm for the second sub-layer of the first side. On the second side 410 mm x 1000 mm was joined with 590 mm x 1000 to form the first sub-layer and the same size boards were joined for the second sub-layer. All fiberboards of this example had horizontal tongue-and-groove joints and none of the joints overlapped. Each sub-layer had a surface area of 1 .0 m². The gypsum boards comprising polyvinyl acetate had a size of 300 mm x 1000 mm, 700 mm x 1000 mm in one layer of either side. The boards were joined to form a total area of 1 .0 m². All gypsum boards in this example were joined vertically such that none of the joints overlapped. The joints between the fiberboards crossed, but did not overlap the joints of the gypsum boards. The dimensions of the building boards as well as the distance between the studs and/or nails were chosen to suit the test requirements. They do not reflect typical building board dimensions.

In all three examples the bullets were flattened after penetrating the first side of the wall assembly.

Claims

Claims A wall assembly (1 ) comprising a sub-structure made of framing members (2) with building boards attached to two opposing sides of the sub-structure to form a first side of a wall and a second side of a wall, wherein

- the first side of the wall comprises at least one layer S1 LF (5) of at least one gypsum fiberboard, wherein the layer S1 LF has a total thickness of at least 25 mm,

- the first side of the wall further comprises at least one layer S1 LG (6) of at least one gypsum board, wherein all of the gypsum boards of layer S1 LG comprise 1 wt.-% to 5 wt.-% polyvinyl acetate based on its solids content, relative to the weight of the gypsum and

- the second side of the wall comprises at least one layer S2LF (7) of at least one gypsum fiberboard, wherein the at least one layer S2LF has a thickness of at least 25 mm and

- a cavity (4) is present between the first side and the second side, wherein the cavity has a thickness of at least 40 mm and is filled with air or an insulation material. A wall assembly (1 ) according to claim 1 , wherein the second side further comprises at least one layer S2LG (8) of at least one gypsum board, wherein any, some or all of the gypsum boards of layer S2LG (8) comprise 1 wt.-% to 5 wt.% polyvinyl acetate based on its solids content, relative to the weight of the gypsum A wall assembly (1 ) according to claims 1 or 2, wherein any, some or all of the gypsum boards of the layer S1 LG (6) and/or all of the gypsum boards of the layer S2LG (8) further comprise glass fibers, preferably 0.5 wt.-% to 2 wt.-% glass fibers, more preferably 0.6 wt.-% to 1 wt.-% glass fibers relative to the weight of the gypsum in the board. 4. A wall assembly (1 ) according to claims 1 to 3, wherein any, some or all of the gypsum boards of the layer S1 LG (6) and/or all of the gypsum boards of the layer S2LG (8) further comprise 0.1 wt.-% to 3 wt.-% starch, preferably 0.1 wt.-% to 1 wt.-% starch based on the weight of the gypsum present in the board.

5. A wall assembly (1) according any of the preceding claims, wherein any, some or all of the gypsum boards of the layer S1 LG (6) and/or all of the gypsum boards of the layer S2LG (8) comprise 2 wt.-% to 4 wt.-% polyvinyl acetate based on its solids content, relative to the gypsum.

6. The wall assembly (1 ) according to any of the preceding claims, wherein any, some or all of the gypsum fiberboards of both layers S1 LF (5) and S2LF (7) have two tongue-shaped edges and two groove-shaped edges such that adjacent gypsum fiberboards can be joined by tongue-and-groove joints, preferably all of the gypsum fiberboard of layers S1 LF (5) and S2LF (7) has two adjacent tongue-shaped edges and two adjacent groove-shaped edges.

7. The wall assembly (1) according to any of the preceding claims, wherein the framing members (2) are made of steel or timber, preferably steel, more preferably steel of at least 0.8 mm gauge, most preferably steel of at least 1 .0 mm gauge.

8. The wall assembly (1 ) according to any of the preceding claims, wherein the layer S1 LF (5) and/or the layer S2LF (7) have a total thickness of at least 50 mm.

9. The wall assembly (1 ) according to any of the preceding claims, wherein the layer S1 LG (6) and/or the layer S2LG (8) have a total thickness of at least 24 mm.

10. The wall assembly (1 ) according to any of the claims 8 or 9, wherein both layers S1 LF (5) and S2LF (7) have a total thickness of at least 50 mm and the layer S1 LG (6) has a total thickness of at least 24 mm.

11. The wall assembly (1 ) according to any of the preceding claims, wherein the first side and the second side of the wall structure are mirror symmetrical.

12. The wall assembly (1 ) according to any of the preceding claims, wherein any, some or all of the gypsum fiberboards and all of the gypsum boards are attached to the sub-structure or to an underlying building board by an attachment means (3), preferably the attachment means are nails, more preferably the attachment means are ballistic nails, most preferably the ballistic nails are made of galvanized carbon steel and/or are fluted and/or have a ballistic tip. The wall assembly (1 ) according to any of the preceding claims, wherein the layer S1 LG (6) and/or the layer S2LG (8) is an outermost layer. Method to build a wall assembly (1 ) comprising a sub-structure made of framing members (2) with building boards attached to two opposing sides of the substructure to form a first side of a wall and a second side of a wall, especially a wall assembly (1) according to any of claims 1 to 13, comprising the following steps:

- positioning at least two framing members (2)

- attaching at least one layer S1 LF (5) of gypsum fiberboard with a total thickness of at least 25 mm on the first side,

- attaching at least one layer S1 LG (6) of gypsum board on the first side, wherein the gypsum board comprises 1 wt.-% to 5 wt.-% polyvinyl acetate

- attaching at least one layer S2LF (7) of gypsum fiberboard with a total thickness of at least 25 mm on the second side and

- providing a cavity (4) between the two opposing sides, wherein the cavity has a thickness of at least 40 mm and is filled with air or an insulation material. Use of gypsum boards in at least one layer S1 LG (6) of a wall assembly (1 ), especially of a wall assembly (1) according to any of claims 1 to 13 or of a wall assembly (1) built according to claim 14, wherein any, some or all of the gypsum boards comprise 1 wt.-% to 5 wt.-% polyvinyl acetate based on its solids content, relative to the weight of the gypsum in the board, to achieve a bullet resistance of the wall assembly, preferably the bullet resistance meets at least the classification of FB6 according to EN1522:1998.