GB2395730A

GB2395730A - Prefabricated external wall for timber frame construction

Info

Publication number: GB2395730A
Application number: GB0227696A
Authority: GB
Inventors: Charles Edward Averill Fowler
Original assignee: Individual
Current assignee: Individual
Priority date: 2002-11-27
Filing date: 2002-11-27
Publication date: 2004-06-02
Also published as: GB0227696D0

Abstract

A prefabricated wall comprises an inner lining layer 1, e.g. of plasterboard, a sheathing layer 2 e.g. of OSB, chipboard, plywood or timber, a layer comprising a wooden structural frame of studs 3 and horizontal members, with interposed insulation 4 of mineral wool or blown cellulose, and an external layer 5 of impregnated softboard or waxed mediumboard.

Description

AN EXTERNAL WALL FOR A BUILDING SYSTEM USING TIMBER

FRAMED CONSTRUCTION FOR HERITAGE HOUSING

DESCRIPTION

The present invention relates to an external wall for a building system for heritage housing and particularly but not exclusively to a building system using a timber framed approach for external walls prefabricated from five horizontally spaced apart layers of construction (external cladding is not part of the system).

External walls are walls which form the outside perimeter of a building which are not party walls separating the building from a different occupancy and which extend from tliG ground floor base up to each intermediate floor and then to the roof level.

External walls must be designed to satisfy a number of different requirements in order to function adequately in service and also to meet the various requirements of building regulations, codes and standards, acceptable good practice and client needs, typically related to structural stability, fire safety, weather resistance, sound insulation, thermal performance, robustness and general serviceability., There are external walls currently in use which meet these design requirements. These walls use timber, steel or concrete as the main structural material together with various other layers of materials. For framed systems, in many cases part of the wall has been prefabricated, usually the basic structural part of the wall comprising the vertical studs and horizontal rails with sheet material or diagonal bracing for wind resistance. This is known as a conventional open wall panel. There are some, but very few, examples of prefabricated closed panel wall systems which comprise the studs and rails with an inner and outer lining and thermal insulation in the structural frame spay. Even with the closed panel systems there are none which include the final internal lining, have improved sound insulation against external noise and have an enhanced level of robustness in terms of resistance to internal impact and the ability to make internal fixings without additional support in the form of naggings.

An object of the present invention is to provide an external wall which is fully prefabricated (apart from external cladding) away from the place where the wall will be used, which meets all the minimum building regulation and good practice requirements and also provides enhanced sound insulation and a greater robustness than conventional external walls. The high level of prefabrication is in order to increase the speed of construction on site, to reduce on-site defects and to increase the quality of the construction. The enhanced sound insulation is to provide improved occupant comfort. The improved robustness is to provide occupants with an enhanced feeling (and actuality) of solidity and to reduce costs and defects associated with provision of support for fixings to internal surfaces.

i According to the first aspect of the present invention relating to the external wall part of the system, there is provided in the external wall a first inner layer which is known as the internal lining.

The internal lining layer normally has at least five functions: o Provision of a level of resistance to moisture to prevent damage from wetting during transport and assembly of the prefabricated wall panels.

O Provision of a substrate for decorative finish.

O Provision of a surface spread of flame classification.

O A contribution to fire resistance of the wall.

O A contribution to sound insulation as a "mass" component.

Preferably the internal lining layer is comprised of a non-combustible, high mass board material with a Class 1 or Class O surface spread of flame classification to the surface facing the room, which is suitable for decoration and thick enough to provide the necessary fire resistance contribution.

Preferably the board material comprising the internal lining layer has a level of resistance to moisture to prevent damage from wetting during transport and assembly of the prefabricated panels. The internal lining layer is fixed to the second inner layer. The internal lining could be moisture resistant plasterboard. According to the second aspect of the present invention relating to the external wall part of the system, there is provided in the external wall a layer second from inside to the inner layer which is known as internal sheathing layer. The internal sheathing layer normally has at least seven functions: o Provision of structural wind bracing.

O Provision of the vapour control layer function to prevent condensation.

a A contribution to airsealing the wall.

O A contribution to sound insulation.

O A contribution to fire resistance.

O Provision of the key resistance to impact damage (robustness).

O A contribution to the ease of fixing services and fittings to the external walls (robustness).

The internal sheath- layer should preferably be a board material which is structural and moisture resistant, has an appropriate vapour resistance, is high density and can contribute to the fire resistance. The internal sheathing layer could be oriented strand board, Shipboard, plywood or solid timber boards but other materials may be equally used.

According to the third aspect of the present invention relating to the external wall part of the system, there is provided in the external wall a layer third from the inside face which Is known as the structural frame spacing layer.

The frame in the structural frame spacing layer normally has at least three functions:

o Provision of structural support to carry the dead and imposed loads of the intermediate floors and roof to the foundations.

O A contribution to the fire resistance of the wall.

a Provision of spacto fit the thermal insulation.

Preferably the structural frame is comprised of timber or timber-based vertical studs and horizontal rails of a size to take the dead and imposed loads and to provide space for insulation suitable to meet the required thermal performance. The said studs and rails are preferably of solid timber or are preferably structural timber composites such as timber l-joists, timber-flanged metal web joists or rectangular section timber composites.

According to the fourth aspect of the present invention relating to the external wall part of the system, there is provided in the external wall a layer, also within the structural spacing layer which is known as the thermal insulation layer fitted in the spaces between the studs and rails.

The thermal insulation layer normally has at least two functions: o Provision of thermal insulation.

O A contribution to the sound insulation as an absorbent layer.

Preferably the thermal insulation layer is a lightweight open-cell insulation material which is fitted tightly up to the sides of the frame so that it forms a continuous vertical layer in all of the spaces between the studs and rails. A typical absorbent layer could be mineral wool insulation of a density of at least 10 kg/m2 but other materials may be equally used; open or closed cell rigid and semi rigid materials of higher density or blown cellulose type products, all to fully fill all of the frame cavities.

According to the fifth aspect of the present invention relating to the external wall part of the system, there is provided in the external wall an outer layer which is known as the external sheathing layer.

The external sheathing layer normally has at least five functions: o Provision of resistance to moisture to prevent damage from wetting during transport and assembly of the prefabricated panels.

a A contribution the in-service resistance to wetting as a line of defence after the external cladding and the drained cavity outside the external sheathing layer. o A contribution to condensation control by allowing the diffusion of water vapour through the wall construction.

a Provision of robustness to resist mechanical and wind damage during transport and assembly before the final cladding is fixed.

a A contribution to wind bracing in certain high wind geographic locations.

The external sheathing layer should preferably be a board material which is moisture resistant, has an appropriate (low) water vapour resistance, can resist mechanical damage and can contribute to the wind resistance when needed. The external sheathing layer could be impregnated softboard or waxed mediumboard.

According to the sixth aspect of the present invention relating to the external wall part of the system, there is provided a method of manufacturing and installing an external wall which comprises: o The provision of all five layers of the external wall, for prefabrication of said wall at a place away from the final position of installation into a building, as one or more compete five-layer panels to make up the said external wall.

O The one or more complete panels of the external wall are taken from the place of manufacture to be assembled into final position in a building; said panels remaining complete as five-layer panels during this transport and installation phase. In one example of this phase, the complete wall panels could be lifted by crane from the place of manufacture onto a lorry, transported by lorry to the building site and lifted by crane into final position in the building.

a The one or more complete panels are installed in the building and joined to the foundations or to the intermediate floor and to each other, all as necessary to make the designed structural connections. The jointing should also take "account of all other design performance requirements - such as fire safety, sound insulation, weathertightness, condensation control, airsealing, and thermal insulation.

Preferably the method of manufacturing and installing the external wall includes providing one or more of the features disclosed in the above paragraphs relating to the first to fifth aspects of the present invention relating to the external wall part of the system.

Embodiments of the present invention will now be described, as one example only of the external wall with reference to the accompanying drawing Figure 1 which shows a plan section of the external wall.

With reference to Figure 1 one embodiment of an external wall in accordance with the present inverition comprises the following: o An internal lining layer (1) of 9mm moisture resistant plasterboard.

O An internal sheathing layer (2) of 1 5mm oriented strand board in accordance with BS EN 300.

a Structural solid timber framing (3), 140x38mm, strength class C16 with studs at 600mm centres.

o A thermal insulation layer (4) which comprises glass wool semi-rigid batts fitted tightly into all frame spaces.

o An outer sheathing layer (5) of 15mm bitumen impregnated softboard Type SB.HLS to BS EN 622-4.

Claims

l CLAIMS

1. An external wall for a building system for heritage housing using a timber framed approach for the external wall, fully prefabricated (except for external cladding) at a place away from the final position in a building in which the wall will be used, comprising of five horizontally spaced apart layers of construction. The wall meets all statutory requirements and provides increased robustness, better buildability with reduced Waste and defects and enables ease of site fixing, and later occupant fixing, for services and fittings and also gives enhanced acoustic performance.

2. An external wall as claimed in Claim 1 where the first inner layer known

as the internal lining may be comprised of a non-combustible, high mass board material with a Class 1 or Class O surface spread of flame classification to the surface facing the room, which is suitable for decoration and thick enough to provide the necessary fire resistance contribution. The board material comprising the internal lining layer may have a level of resistance to moisture to prevent damage from wetting during transport and assembly of the prefabricated panels. The internal lining could be moisture resistant plasterboard.

3. An external wall as claimed in Claim 1 and Claim 2 where the layer second from inside to the inner layer is known as the internal sheathing layer which could be comprised of a board material which is structural and moisture resistant, has an appropriate (high) vapour resistance, is of high density and can contribute to the fire resistance. The internal sheathing layer could be oriented strand board, shipboard, plywood or solid timber boards but other materials may be equally used.

4. An external wall as claimed in Claims 1, 2 and 3 where the layer third from the inside face is known as the structural frame spacing layer which could be comprised of timber or timber-based vertical studs and horizontal rails of a size to take the dead and imposed loads and to provide space for insulation suitable to meet the required thermal performance. The said studs and rails could be solid timber or structural timber composites such as timber l-joists, timber-flanged metal web joists or rectangular section timber composites.

5. An external wall as claimed in Claims 1, 2, 3 and 4 where there is, also within the structural spacing layer, a layer known as the thermal insulation layer fitted in the spaces between the studs and rails which could be comprised of lightweight open-cell insulation material which is fitted tightly up to the sides of the frame so that it forms a continuous vertical layer in all of the spaces between the studs and rails. A typical absorbent layer could be mineral wool insulation of a density of at least O kg/m i

6. An external wall as claimed in Claims 1, 2, 3, 4 and 5 where there is outer layer which is known as the external sheathing layer which could

be comprised of a board material which is moisture resistant, has an appropriate (low) water vapour resistance, can resist mechanical damage and can contribute to the wind resistance when needed. The external sheathing layer could be an impregnated softboard or a waxed mediumboard.

7. A method of manufacturing and installing an external wall as claimed in any previous claim which comprises: The provision of all five layers of the external wall, for prefabrication of said wall at a place away from the final position of installation into a building, as one or more complete five-layer panels to make up the said external' wall.

The one or more complete panels of the external wall are taken from the place of manufacture to be assembled into final position in a building; said panels remaining complete as five-layer panels during this transport and installation phase The one or more complete panels are installed in the building and joined to the foundations and to each other, all as necessary to - make the designed structural connections.

8. An external wall for a building system for heritage housing, substantially as described herein with reference to Figure 1, the accompanying drawing.

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