WO2006111723A1

WO2006111723A1 - System and method for forming a base for an extension to an existing structure and components useful in the system and method

Info

Publication number: WO2006111723A1
Application number: PCT/GB2006/001397
Authority: WO
Inventors: Michael Morphet
Original assignee: Ultraframe (Uk) Limited
Priority date: 2005-04-20
Filing date: 2006-04-19
Publication date: 2006-10-26
Also published as: GB0507951D0; GB2425318A

Abstract

A system for forming a base for a wall, which may be suitable for a wall of a conservatory or other extension to an existing building, uses formwork units (42) that comprises spaced panels connected by webs, wherein the units are positioned and the space between the panels (48, 50) filled with concrete or other suitable settable material. A floor slab (62) for the extension can be poured at the same time as the formwork units are filled.

Description

Title: System and method for forming a base for an extension to an existing structure and components useful in the system and method.

DESCRIPTION

This invention concerns a system and a method for forming a base suitable for constructing an extension to an existing structure. The invention also concerns formwork units for use in the system and method.

Conventionally forming a base for a building involves digging a trench, pouring a layer of concrete into the trench to form the footings and building up a stem wall up to the desired height of the floor of the building. Subsequently a hardcore layer, a damp proof membrane, an insulation layer and a concrete floor slab are added within the boundary formed by the stem wall. However, the stem wall cannot be built until the footings have set and the concrete slab cannot be laid until the stem wall has set. Also, cold bridges can form between the concrete slab and the footings, which is undesirable.

An object of the invention is to provide an improved system for forming a base suitable for constructing an extension to an existing structure.

According to the invention a system for forming a base for a wall, which may be suitable for a wall of a conservatory or other extension to an existing building, uses formwork units that comprise spaced panels connected by webs, wherein the units are positioned and the space between the panels filled with concrete or other suitable settable material. The invention further provides a method of forming a base for a wall, which may be a wall of a conservatory or other extension to an existing building, comprising aligning formwork units, usually in a trench, the units comprising spaced panels connected by webs, and filling the space between the panels with concrete or other suitable settable material.

The method of the invention preferably also includes the step of pouring the floor slab for the extension or other building structure at the same time as forming the base.

The filling of the formwork units with concrete or other settable material forms the stem wall that acts as the boundary for the floor slab. Instead of building up the structure wall entirely on the stem wall, it is possible to build the outer wall skin on the stem wall and to build the inner skin on the slab itself.

The invention also provides a formwork unit for use in forming a base for a wall and, which may be a wall of a conservatory or other extension to an existing building, and optionally a floor slab at the same time, the formwork units comprising spaced panels connected by webs.

The formwork units of the invention are preferably formed of insulating material, such as of plastics material, especially of foamed or expanded plastics material, such as expanded polystyrene. The panels and webs may be formed as a unitary moulding or may be formed as separate items. Webs may have their ends moulded into the panels or may have their ends provided with formations for connection with complementary formations of the panels.

The preferred formwork units of the invention have intended inner and outer panels relative to a structure being built on the footings depending on the type of foundation required for the ground conditions. The preferred formwork units of the invention have one panel of greater height than the other panel. For some foundation systems, the panel of greater height will be the inner panel. The top edge of the outer panel may then provide a level for the concrete filling the unit and the top edge of the inner panel may provide a level for the top of a concrete slab forming the floor of the structure being built.

For ground conditions where the slab needs to be of a raft type, the formwork units can be used the other way round, so that the outer panel is the panel of greater height. Then the top edge of the outer panel may provide a level for the top of the raft.

If necessary the slab may be formed with metal reinforcement therein.

The panels of the formwork units of the invention may have ribbing or other strengthening features on their outer surfaces.

Ideally, the formwork units of the invention will have means for restraining movement thereof when the concrete other settable material is being poured into them. In one preferred form, the panels have outer ledges along bottom edges thereof. These ledges may be useful for retaining the units in position for concrete pouring by being covered by backfilling to hold them down before concrete pouring.

AQ alternative may be to provide bridges between lower parts of the panels, which may be held down by initial concrete pouring.

Connecting webs of formwork units of the invention are preferably shaped to provide surface friction or interference with the concrete to help counteract any buoyancy problems arising form the lightness of the units. The units may, of course, be weighted in some way to counteract buoyancy problems. Another means of retaining formwork units in position for concrete pouring may be to use stakes or posts. Outer faces of the panels or ledges thereof may be provided with grooves, slots or channels which receive and direct the stakes or posts to be driven into the ground, the grooves, slots or channels and the stakes or posts having mutually retaining cross-sections, such as dovetail sections.

Additionally or alternatively to counteract movement of the formwork units either due to dislodgement by the concrete or due to buoyancy, it is envisaged that the concrete used for forming a base has a low slump. The concrete may be made as a relatively dry mix and /or contain aggregate of selected size.

In many situations it is envisaged that footings will not be required for forming a base for a structure in accordance with the invention. It may be necessary to provide footings where ground conditions are such that a spread load-bearing base is needed. Nevertheless, it is possible to provide formwork units according to the invention that can allow for some lateral spread of concrete. For example, bottom edges of panels of formwork units of the invention may have transverse passages to allow concrete poured into the formwork units to spread laterally. hi order to facilitate setting out of formwork units of the invention prior to concrete pouring, a number of options are possible. Levelling of the units is an important aspect of the invention and so it is proposed that each unit be provided with an integral spirit level bubble in a top surface thereof. Preferably also levelling means is provided for a formwork unit of the invention. Such levelling means may take the form of height adjustable feet or the unit may be height adjustable relative to support members, on which the unit sits. To assist further with the setting out of the formwork units, it is envisaged that the will have surface markings to indicate key set out points, such as the heights of the hardcore and slab and positions for reinforcement. Other markings may be provided on the units, especially corner units, to aid with alignment thereof, such as pimples or depressions formed in the moulding or separate items, such as pins.

Formwork units of the invention may also be provided with end formations enabling them to be linked. Such formations are preferably of male and female type. Preferably a unit of the invention has a dovetail section groove at one end and a dovetail section protrusion on the other end, so that units can be linked by sliding the dovetail protrusion at the end of one unit into the dovetail groove of the next unit.

Preferred formwork units of the invention have a wider base laterally of its panels than top. The panels preferably have flared lower parts relative to each other.

When forming a base for a building structure a damp proof membrane will usually be required and this will be laid before the slab or raft is poured. Therefore, it will be useful for formwork units of the invention to have means for capturing edges of a damp proof membrane to prevent it from being pulled out of position as the concrete is being poured onto it. Such capturing means are preferably provided on the inside or outside of the higher of the panels making up a formwork unit.

The use of formwork units of the invention allows for the concrete filling the units and the concrete for the floor slab to be poured at the same time, so reducing the time on site. There may also be cost savings as a result of using less concrete by omitting footings and by needing only a narrower trench when the inner wall skin of the structure is built on the floor slab. The formwork units according to the invention can be manufactured in a factory to a consistent standard and can be provided with set out markings. Therefore, they can be set out accurately on site and may act as a template for subsequent building work to create the building structure, hi other words the setting out for the whole structure can be carried out in the foundations rather than after the foundations have been completed, which may provide for greater accuracy than with prior art building methods.

Furthermore, the formwork units may be made of a materials that can be carved or cut relatively easily, so that they can be shaped to avoid underground obstructions, such as pipes or the like.

Also, it is usual to put down a layer of insulation before the concrete slab is poured and the preferred formwork unit will have its inner panel extending up to the top of the slab, so that there will be an insulating barrier between the concrete slab and the concrete filling the formwork unit. In other words gaps insulation may be avoided.

Formwork units of the invention may also have locations for receiving structural posts, such as in the form of pockets. The structural posts preferably project upwards to provide stability for the super structure.

This invention will now be further described, by way of example only, with reference to the accompanying drawings, in which;

Figure 1 illustrates a prior art method of forming a base for building structure;

Figure 2 illustrates a method according to the invention of forming a base for a building structure;

Figure 3 follows on from Figure 2 with the wall added; Figure 4 illustrates a prior art method of forming a base for a structure including a raft type floor slab;

Figure 5 illustrates a method according to the invention of forming a base for a building structure including a raft type floor slab;

Figure 6 shows a first formwork unit for use in the invention;

Figures 7a and 7b are end and front views respectively of a second formwork for use in the invention;

Figure 8 shows a third formwork for use in the invention;

Figure 9 shows a fourth formwork for use in the invention;

Figure 10 shows a fifth formwork for use in the invention;

Figure 11 shows a sixth formwork for use in the invention;

Figure 12 shows a seventh formwork for use in the invention;

Figure 13 shows an eighth formwork for use in the invention;

Figure 14 is an exploded view of another formwork unit of the invention;

Figure 15 shows the formwork unit of Figure 14 assembled;

Figure 16 shows a corner formwork unit; and

Figure 17 shows a foundation assembly of formwork units of Figures 15 and 16.

Referring to Figure 1 of the accompanying drawings, a current base for a building structure, such as for a conservatory, requires a trench 10 to be dug, into which a concrete layer 12 is poured and allowed to set. Usually the next day a stem wall is added in the form of inner and outer unit work skins 14, 16 and then hardcore 18, followed by a sand blinding screed 20, a damp proof membrane 22, a layer of insulation 24 and a concrete floor slab 26 within the boundary formed by the inner skin 14. Wall 8 of the conservatory is then built up usually from brick for the outer skin 16 and from units for the inner skin 14 with insulation 28 between. On the wall 8 windows (not shown) are mounted. Using this method there are delays between stages to allow for concrete and mortar to set.

Turning to Figures 2 and 3 of the accompanying drawings, instead of using masonry work to form the stem wall for a wall 40, such as for a conservatory, an expanded polystyrene formwork unit 42 is used. As before, a trench 44 is dug and the formwork units 42 are laid in the trench end to end.

The formwork units 42 have opposed spaced panels 48, 50 connected by upper and lower, webs 52, 54. The panels 48, 50 are of different heights, the intended inner panel 48 being higher than the intended outer panel 50. The space between the panels receives concrete 56 to form with the formwork units 42 the footings and the stem wall for the wall 40. The panels 48 and 50 have diverging lower parts, so that the formwork units when filled with concrete provide a wider base. Also the bottom edges of the panels have out ward facing ledges, which can be secured to the ground to restrain movement of the units as they are being filled with concrete.

The inner panel.48 has a top edge 60 that provides a level for concrete slab 62 and the outer panel 50 has a top edge 64 that provides a level for the concrete 56 poured into the space between the panels.

The units 42 will usually be held in place by backfilling 65 either side thereof and sand blinding screed 66, damp proof membrane 68 and insulation layer 70 are added. The concrete 56 to complete the stem wall and the floor slab 62 can then be poured at the same time. The concrete used for forming the base has a low slump. The concrete may be made as a relatively dry mix and /or contain aggregate of selected size.

Once the stem wall and the floor slab have set, the inner and outer skins of the wall of the building structure can be built. As shown in Figure 3, it is envisaged that the outer skin 72 of the wall 8 will be built on top of the concrete filling the formwork units and the inner skin 74 will be built on top of the floor slab 62 with insulation 16 between the skins.

The use of the polystyrene formwork units to create the footings has a number of advantages. Firstly, the formwork units provide better insulation or no cold bridges, because the inner panel separates the concrete slab from the concrete filling the formwork. Secondly, it is possible to pour the concrete slab and the concrete in the footings at the same time, so that time on site can be reduced. Also, there may be savings in material costs.

In Figure 4 of the drawings a conventional building structure base is shown having a raft type floor slab, i.e. where the floor slab extends over the stem wall, hi a trench 80 a concrete foundation 82 is laid followed by a trench block 84 and units or bricks building up the stem wall inner skin 86 to ground level and the outer skin 88 to the desired height for the floor slab 90. After laying down a damp proof membrane 92, which extends across the inner skin and over the outer skin, the concrete floor slab is poured within the boundary formed by the outer skin.

In accordance with the invention as shown in Figure 5, a building structure base with a raft type floor slab 91 is constructed using formwork units 42 as shown in Figures 2 and 3 but the opposite way round. As previously a trench 93 is dug and the formwork units laid in the trench end to end with the higher panels outwards. After putting down a hardcore layer 94 followed by a sand blinding screed 96, the damp proof membrane 97 and a layer of insulation 98, concrete 99 is poured into the formwork units up to the level of the inner panel, the damp proof membrane extended over the outer panel of the formwork and the concrete poured to form the floor slab. Thus, without having to wait for any foundations or stem wall construction to set, the stem wall and the floor slab can be formed almost in one go.

In Figure 6 a formwork unit 100 suitable for use in place of the formwork unit 42 is shown comprising a pair of panels or walls 102, 103 of moulded expanded polystyrene connected by upper and lower webs 104 and 106 respectively.

The walls 102 has a greater height than that of wall 103 for the reasons mentioned with reference to the walls of formwork unit 42 of Figure 2. Both walls have a lower wide part 108 and a tapered upper art 110. The tapered part 110 has an inner face 112 aligned with the inner face of the wide part and an outer face 114 that is stepped in from the outer face of the wide part of 116.

The lower webs 106 are in the form of rods or bars that extend into the walls 102, 103. The upper webs 104 are in the form of straps whose ends fit over the top edges of the walls 102, 103.

The formwork unit 100 is also shown with a cradle 120 that can be used for levelling the unit. A pair of cradles will be provided for a unit. The cradles and the units are interference fits, so that the height of the unit relative to each cradle can be adjusted with the unit being gripped in the ends of the cradles. This arrangement may be applicable to any other formwork unit according to the invention. Turning to Figures 7 A and 7B a formwork unit 150 for use in the invention is made of a pair of moulded expanded polystyrene panels 152, 154 connected by upper and lower webs 156 and 158 that are of polycarbonate or other more rigid plastics material than the panels. The webs may have their ends moulded into walls or may have ends shaped to engage with formations of the panels.

The panels 152, 154 have outer ribbing 158 for strength.

Figures 8 and 9 show formwork units 250 and 300 for use in the invention, both of which are made as unitary mouldings from expanded polystyrene. In Figure 8 the formwork unit 250 has outwardly stepped sidewalls 252 and 254, so that the unit when filled with concrete has a wide base. One sidewall 252 is higher than the other sidewalL The sidewalls are connected top and bottom by upper and lower webs 256 and 258 respectively. Indents 260 from the bottom edge of each sidewall are provided for location of levelling feet or cradles. hi Figure 9, main difference over the embodiment of Figure 8 lies in the shaping of upper webs 302, which slope downwards from higher sidewall 304 to a midpoint of the web before a level part 306 to the lower height sidewall 308. The formwork unit 300 will be filled up to the level of the web part 306 and the shaping of the webs allows for masonry to be erected on the concrete without being impeded by the webs.

In Figure 10 of the accompanying drawings, an insulating concrete formwork unit 400 is made up of a pair of opposed, spaced panels 402 that are connected by webs 406 A or B. The panels 402, 404 have on their intended inner faces dovetail grooves 408, into which locate dovetail formations 410 at the ends of the webs 406 to hold the panels together at a desired spacing. The panels 402, 404 are usually made of expanded polystyrene. The webs 406A may be made of expanded polystyrene or 406B of a more rigid plastics material.

Turning to Figure 11 of the drawings, a formwork unit variation 500 is shown, in which panels 502, 504 are connected by webs (not shown). The panels have ledges 506 along the bottom of their outer sides. These ledges 506 can be covered by back filling (508) to retain the formwork in the ground and to prevent tilting when concrete is poured into the formwork.

An alternative formwork 600 to that shown in Figure 11 is shown in Figure 12, wherein the panels 602 forming the sides of the formwork have their ledges 604 castellated both from the underside 606 and from the side 608. This shaping aids spread of concrete to provide a wider bearing surface.

Turning to Figure 13 of the accompanying drawings panes 702 for a formwork unit 700 have a ledge 704 along their outer bottom edge. The ledge has transverse channels 706 in its underside to aid spread of concrete as in the embodiment of Figure 12. Above the ledge are dovetail section grooves 708 extending downwards through the ledge. These grooves are to receive stakes or posts 710 to secure and level the formwork units in situ.

In Figure 14 there is shown the components, typically of expanded polystyrene, for making in to a formwork unit 800 as shown in Figure 15. The formwork unit components comprise lower side panels 802 and upper side panels 804 and 806 of different heights. The top edges of the lower side panels have spaced projections that locate in corresponding recesses on the intended bottom edges of the upper side panels 804 and 806. Thus, the assembled unit has one side higher than the other. The lower side panels flare outwardly to a bottom ledge 810. The flared sections 812 have outwardly of the assembled unit vertical holes 814 to receive stakes or the like for securing the unit to the ground. Also along the lower parts of the side panels are spaced lateral open- bottomed channels 816 to allow concrete filling the formwork unit to spread to provide a wider concrete base.

The side panels are connected by upper and lower web components 818 and 820 respectively. The side panels have vertical grooves 822 for receiving edges 824 of the webs in locking fashion, such as by means of tongue and groove formations. One end of a side panel has a groove 826 and the opposite end has a tongue 828, so that formwork units can be located end to end by insertion of the tongue of one unit into the groove of the adjacent unit.

Additionally the side panels have their facing surfaces grooved vertically (829) to provide for better interference between the units and the concrete filling them.

Figure 16 of the drawings shows an outer side panel 830 for use in forming a corner formwork unit 832 (see Figure 17). Construction of a corner unit is generally the same as a straight unit.

Figure 17 of the drawings shows how a base for a three sided extension can be created using the formwork units 800 and 832, although the general principle applies to the use of any of the illustrated and described formwork units. An advantage of this system is that the formwork units can be prepared off site to size and then reassembled on site and used as a template for setting out of the structure to be built.

Claims

1. A system for forming a base for a wall, which may be a wall of a conservatory or other extension to an existing building, using formwork units that comprise spaced panels connected by webs, wherein the units are positioned and the space between the panels filled with concrete or other suitable sellable material.

2. A system for forming a base for a wall, which may be a wall of a conservatory or other extension to an existing building, and for forming a floor slab for the extension using formwork units that comprise spaced panels connected by webs, wherein the units are positioned and the space between the panels filled with concrete or other suitable settable material and a boundary formed by the units filled to form the slab.

3. A system as claimed in claim 2, wherein pouring the floor slab for the extension is carried out at the same time as the filling of the formwork units.

4. A system as claimed in claim 1, 2 or 3, wherein lower parts of the panels diverge.

5. A system as claimed in any one of claims 1 to 4, wherein the formwork unit is formed of expanded polystyrene.

6. A system as claimed in any one of claims 1 to 5, wherein the formwork unit is formed as a unitary moulding.

7. A system as claimed in any one of claims 1 to 6, wherein the webs and panels of the formwork units are formed as separate items.

8. A system as claimed in any one of claims 1 to 7, wherein the formwork units having intended inner and outer panels relative to a structure being built.

9. A system as claimed in any one of claims 1 to 8, wherein the formwork units have set out indications thereon.

10. A system as claimed in any one of claims 1 to 9, wherein the formwork units have means for checking levelling thereof.

11. A system as claimed in claim 10, wherein the checking means is an integral spirit level.

12. A method of forming a base for a wall, which may be a wall of a conservatory or other extension to an existing building, comprising aligning formwork units, usually in a trench, the units comprising spaced panels connected by webs, and filling the space between the panels with concrete or other suitable settable material.

13. A method as claimed in claim 12, wherein pouring a floor slab for the extension is carried out at the same time as the filling of the formwork units.

14. A method as claimed in claim 12 or 13, wherein the formwork units are formed of expanded polystyrene.

15. A method as claimed in claim 12, 13 or 14, wherein the formwork units are formed as unitary mouldings.

16. A method as claimed in any one of claims 12 to 15, wherein the webs and panels of the formwork units are formed as separate items.

17. A method as claimed in any one of claims 12 to 16, wherein the formwork units have intended inner and outer panels relative to a structure being built.

18. A method as claimed in any one of claims 12 to 17, wherein the formwork units have set out indications thereon.

19. A method as claimed in any one of claims 12 to 18, wherein the formwork

units have means for checking levelling thereof.

20. A method as claimed in claim 19, wherein the checking means is an integral spirit level.

21. A formwork unit for use in forming a base for a wall, which may be a wall of a conservatory or other extension to an existing building, comprising spaced panels connected by webs.

22. A formwork unit as claimed in claim 21, wherein lower parts of the panels diverge.

23. A formwork unit as claimed in claim 21 or 22 formed of expanded polystyrene.

24. A formwork unit as claimed in claim 21, 22 or 23 formed as a unitary moulding.

25. A formwork unit as claimed in claim 21, 22 or 23, wherein the webs and panels are formed as separate items.

26. A formwork unit as claimed in any one of claims 21 to 25 having intended inner and outer panels relative to a structure being built.

27. A formwork unit as claimed in any one of claims 21 to 26 having setting out indications thereon.

28. A formwork unit as claimed in any one of claims 21 to 27 having means for checking levelling thereof.

29. A formwork unit as claimed in claim 28, wherein the checking means is an integral spirit level.