GB2604372A

GB2604372A - Insulating concrete formwork

Info

Publication number: GB2604372A
Application number: GB2103013.5A
Authority: GB
Inventors: Wheeler Alan
Original assignee: Greenraft Ltd
Current assignee: Greenraft Ltd
Priority date: 2021-03-03
Filing date: 2021-03-03
Publication date: 2022-09-07
Also published as: GB202103013D0

Abstract

An ICF structure includes a base layer (1) of thermal insulation material, a concrete slab (2) supported on the base layer, an outer wall skin (10) of thermal insulation material located on the base layer, and an inner wall skin (12) of thermal insulation material which is spaced from the outer wall skin. The inner wall skin (12) is supported on mutually spaced I-shaped support elements (13) interposed between the inner wall skin and the base layer (1) and an intermediate concrete layer (28) between the inner and outer wall skins is integrally formed with the concrete slab through gaps between the support elements (13).

Description

Greenraft Limited

INSULATING CONCRETE FORMWORK

TECHNICAL FIELD OF THE INVENTION

This invention relates to insulating concrete formwork as used in the construction of buildings.

BACKGROUND

Insulating concrete formwork (ICE) is increasingly being used in building construction. A formwork with inner and outer skins is constructed from blocks of lightweight thermal insulation material. The two skins are joined by spaced cross-ties to form a continuous cavity into which concrete is pumped. When the concrete hardens the skins provide permanent insulating layers on opposite sides of the concrete core. In one particular system which is supplied by Polarwall Limited of Exeter, top and bottom faces of the insulating blocks are connected by H-rails which are in turn interconnected by plastic cross-ties which snap-engage with the H-rails. The bottom-most course of blocks may be seated on U-rails which are also also connected by similar cross-ties. When the position of the walls is laid out on site the U-rails can be accurately positioned and fastened to a pre-laid concrete foundation or floor slab. -2 -

ICF may be also be constructed from other materials or used with other construction methods. For example, the wall skins may incorporate an insulated steel or timber frame. Structural insulated panels (SIPs), manufactured off-site under factory controlled conditions, are often used in residential and light commercial construction. These panels include an insulating foam core sandwiched between two structural facing sheets, typically oriented strand board (OSB). Such timber walls may be supported on a short ICF upstand.

Often a concrete floor slab is constructed on a base layer of thermal insulation material which is first laid over compacted aggregate blinded with a thin layer of sand. Normally the floor slab is constructed in one pour which is contained by closer blocks formed of thermal insulation material. The closer blocks and the boards forming the insulation layer may be prefabricated off-site. The closer blocks may, for example, slot into pre-formed channels in the insulating base layer. Another method uses L-shaped blocks which form the closers and part of the floor insulation. Once the floor slab has set the inner and outer skins of the formwork are secured to the floor slab and/or the closer blocks in the required positions so that the wall cavity within the formwork can be filled with concrete.

This process is time consuming and is also costly both in terms of labour and the number of concrete deliveries which are required accompanied by suitable placement equipment. -3 -

Note: The term 'concrete' as used herein is intended to embrace traditional self-setting compositions based on portland cement as well as more recent environmentally acceptable alternative cennentitious materials such as Alkaline Activated Materials (AAM) and geopolymers.

SUMMARY OF THE INVENTION

When viewed from one aspect the present invention proposes insulating concrete formwork: - a loadbearing structure (1); - a concrete slab (2) supported by the loadbearing structure; - an outer wall skin (10) of thermal insulation material; - an inner wall skin (12) of thermal insulation material which is spaced from the outer wall skin; - an intermediate concrete layer (28) between the inner and outer wall skins; wherein the inner wall skin (12) is supported on a plurality of mutually spaced support elements (13) interposed between the inner wall skin and the loadbearing structure (1) and wherein the intermediate concrete layer (28) is integrally formed with the concrete slab through gaps between the support elements (13).

In a preferred embodiment each support element is substantially I-shaped with a base member and a top member connected by an -4 -upright member. In a preferred embodiment the base member and the top member are substantially parallel.

In a preferred embodiment the top members of the support elements are received in H-rails which are in turn engaged with the inner wall skin.

In a preferred embodiment inner faces of the H-rails have ribs which engage in longitudinally extending grooves formed in the top members of the support elements.

In a preferred embodiment the H-rails are engaged with the outer wall skin by cross-ties.

In a preferred embodiment the cross ties engage H-rails which are in turn engaged with the outer wall skin.

In a preferred embodiment the base members of the support elements are received in U-rails which are in turn engaged with the loadbearing structure.

In a preferred embodiment inner faces of the U-rails have ribs which engage in longitudinally extending grooves formed in the base members of the support elements.

In a preferred embodiment the U-rails are engaged with the outer wall skin by cross-ties. -5 -

In a preferred embodiment the cross ties engage U-rails which receive the bottom of the outer wall skin.

In a preferred embodiment the support elements are cast from concrete.

In a preferred embodiment the loadbearing structure comprises a base layer of thermal insulation material which supports the concrete slab.

In a preferred embodiment the base layer of thermal insulation material supports closer blocks which are spaced from the outer wall skin by a concrete foundation strip.

In a preferred embodiment the outer wall skin is formed with apertures and wherein the concrete foundation strip is integrally formed with the concrete slab through said apertures.

In a preferred embodiment the concrete foundation strip supports a hard wall facing.

In a preferred embodiment a layer of structural thermal insulation material is interposed between the concrete foundation strip and the hard wall facing.

The invention also provides a method of constructing insulating concrete formwork: -providing a loadbearing structure (1); -6 - - providing a concrete slab (2) supported by the loadbearing structure; - providing an outer wall skin (10) of thermal insulation material; - providing an inner wall skin (12) of thermal insulation material which is spaced from the outer wall skin; - providing an intermediate concrete layer (28) between the inner and outer wall skins; wherein the inner wall skin (12) is supported on a plurality of mutually spaced support elements (13) interposed between the inner wall skin and the loadbearing structure (1) and wherein the intermediate concrete layer (28) is integrally formed with the concrete slab (2) through gaps between the support elements (13).

In a preferred embodiment the method includes providing a loadbearing structure (1) comprising a base layer of thermal insulation material which supports the concrete slab (2).

In a preferred embodiment the method includes providing on the base layer closer blocks which are spaced from the outer wall skin by a concrete foundation strip.

In a preferred embodiment the method includes providing the outer wall skin with apertures and integrally forming the concrete foundation strip with the concrete slab through said apertures.

In a preferred embodiment the method includes providing a hard wall facing supported on the concrete foundation strip. -7 -

In a preferred embodiment the method includes providing a layer of structural thermal insulation material between the concrete foundation strip and the hard wall facing.

BRIEF DESCRIPTION OF THE DRAWINGS

The following description and the accompanying drawings referred to therein are included by way of non-limiting example in order to illustrate how the invention may be put into practice. In the drawings: Fiaure 1 is a transverse cross-sectional view of an ICF structure as constructed to support a timber frame building; Figure 2 is a vertical section through the ICF structure; Figure 3 is a general view of an I-block support element as used in the ICF structure; Fiaure 4 is a general view of two H-rails used to connect the two wall skins of the ICF structure; Fiaure 5 is a transverse cross-sectional view of a second form of ICF structure as used to support a timber frame building with external brick or stone cladding; -8 -Fiqure 6 is a general view of two U-rails used to connect the bottom of the inner and outer wall skins of the ICE structure; Figure 7 is a side view of a bottom region of the outer ICF wall skin shown in Fig. 5.

DETAILED DESCRIPTION OF THE DRAWINGS

Fig. 1, shows a loadbearing structure in the form of an insulated slab as used to construct the ground-bearing floor of a timber frame building. Following site excavation, compacted hardcore is laid over the sub-soil and then blinded with a thin layer of sand. A base layer 1 of thermal insulation boards, e.g. extruded polystyrene, are laid edge-to-edge to support a poured concrete floor slab 2 which contains a steel reinforcement 3. The edge of the slab is defined by a line of closer blocks 4 of a depth equal to the required depth of the poured slab. The closers 4 may be of similar thermal insulation material to the boards 1 and are laid out on site and fixed to the boards in the measured positions according to a design specification. Fixation of the closers may be achieved by any suitable means, with or without adhesive, e.g. insertion into pre-formed slots in the insulating floor layer 1, the use of L-shaped blocks, etc. In this first embodiment the row of closer blocks 4 supports the -9 -outer wall skin 10 of an ICE wall upstand 11. The outer wall skin 10 and an inner wall skin 12 are both constructed from blocks of thermal insulation material which are placed in situ before the floor slab 2 is poured. Referring also to Fig. 2, the inner skin 12 is constructed on mutually spaced support elements 13 which are positioned on the thermal insulation layer 1. Each support element, one of which is shown separately in Fig. 3, is generally I-shaped with with a longitudinal base member 14 and a substantially parallel longitudinal top member 15. The mid-length regions of the two longitudinal members are interconnected by an integral upright member 16. Opposite side faces of the top member 15 are provided with longitudinally extending grooves 17. In addition, opposite side faces of the base member 14 are preferably provided with similar longitudinally extending grooves 18, the function of which will be explained below.

Referring back to Fig.s 1 and 2, the blocks forming the outer and inner wall skins 10 and 12 are seated on an H-rail system shown in Fig. 4. Respective H-rails 19 and 20 are incorporated in the outer and inner wall skins 10 and 12, with the insulation blocks either being slotted into the H-rails or, in the case of wider blocks as shown, having slots cut into the blocks to receive the H-rails, e.g. using a standard circular saw blade. The H-rails 19 and 20 are both provided with arrowhead flanges 21 which are joined at intervals by moulded plastic tie rods 22 which are snap-engaged with the flanges 21. Furthermore, the opposing inner surfaces of each H-rail have shallow longitudinally extending ribs 23 which bite into the insulation blocks, thereby firmly securing the blocks -10 -to the rails.

As can be seen in Fig.s 1 and 2, the H-rails 20 supporting the inner wall skin 12 engage over the top members 15 of the support elements 13. The H-rails are held to the support elements by engagement of the ribs 23 in the grooves 17. Additional courses of insulation blocks which form the ICF wall skins 10 and 12 may be held together by similar H-rail systems 19, 20, as shown, depending upon the height of the ICF wall or upstand. It will also be noted that the steel reinforcement bars 3 extend into the space between the inner and outer wall skins 12 and 10. When the concrete is poured to form the floor slab 2 the concrete passes between the support elements 13 spilling into the space between the support elements and the closer blocks 4. In addition, during the same placement operation, the concrete may be fed into the intermediate space 28 between the wall skins, thereby forming an integral bond with the floor slab when the concrete hardens. In the case of a SIPS or timber wall, the wall upstand may be capped by a wooden wall plate 25 which is inserted into the top of the upstand and tied to the set concrete using embedded anchor bolts 26.

To ensure good bonding the support elements 13 are preferably cast of concrete although other suitable materials could be used such as stainless steel or recycled plastics.

Although the above example relates to a ground floor slab a similar arrangement can be used in relation to suspended concrete floor slabs, e.g. in an upper floor of a building. The loadbearing structure which supports the floor slab may include joists or beams which are in turn supported by the ground floor wall. The support elements are fixed on the ground floor wall so that the floor slab is integrally formed with the intermediate concrete layer within the insulating concrete formwork.

In some timber-frame walls the external surface is clad with a hard facing material such as brick or stone. Fig. 5 shows how a concrete floor slab with an integrated ICF structure can be modified to support such cladding. As in the previous embodiment, compacted hardcore 30 is blinded with a thin layer of sand 31. Thermal insulation boards 1, e.g. of extruded polystyrene, are laid edge-to-edge to support a poured concrete floor slab 2 containing a steel reinforcement 3. The edge of the slab is defined by a line of closer blocks 4 of similar thermal insulation material to the boards 1. The closers are laid out on site and fixed in the measured positions.

Outer and inner wall skins 10 and 12 of an ICF wall upstand 11, constructed from blocks of thermal insulation material, are constructed on the insulation boards 1 inside the boundary formed by the closers 4 before the floor slab 2 is poured. The wall skins may be secured in position on the insulation boards by a U-rail system which is shown in Fig. 6. Respective U-rails 39 and 40 support the outer and inner wall skins 10 and 12. The U-rails are both provided with arrowhead flanges 41 which are in turn joined at intervals by thermoplastic tie rods 42 which are snap-engaged -12 -with the flanges 41. Furthermore, the opposing inner surfaces of each U-rail have shallow longitudinally extending ribs 43 which bite into the insulation blocks when engaged with the rails.

As can be seen in Fig. 5, the inner wall skin 12 is constructed on I-shaped mutually spaced support elements 13 which are as described above in relation to Fig. 3. The U-rails 40 supporting the inner skin 12 receive the base members 14 of the support elements 13 which they engage by location of the ribs 43 in the grooves 18. The blocks forming the outer wall skin 10 are also engaged in the U-rails 39, but as shown in Fig. 7, the bottom blocks 46 are castellated at their lower edges forming through-apertures 47.

Further courses of blocks which form the inner and outer wall skins 10 and 12 may be connected by H-rails and tie rods 19, 20 and 22 as described above. The upper edge of the wall upstand which supports a timber SIP or wall frame 50 may be closed by wall plates 25 and anchor bolts 26, as in Fig. 1, but an alternative arrangement, which is shown in Fig. 5, uses inverted U-rails and tie rods 39, 40 and 42.

The steel reinforcements 3 extend between the support elements 13 into the space between the inner and outer wall skins 12 and 10, and also extend further through the apertures 47 in the outer wall skin 10. When the concrete is poured to form the floor slab 2 the concrete spills between the support elements 13 filling the space between the wall skins. During the same pouring operation, the -13 -concrete may be fed into the space 28 between the wall skins, thereby forming an integral bond with the floor slab. In the same pour, concrete can be fed through the apertures 47 in the outer wall skin 10 to form an integral concrete foundatiOn strip 52 between the closer blocks 4 and the outer wall skin 10. When the concrete has cured a layer of structural thermal insulation material 55 such as cellular glass' is placed over the foundation strip 52 to provide a thermally insulated foundation for construction of an external hard wall facing 56, e.g. brick or stone.

Inside the building the floor slab 2 may be finished as required, e.g. covered by a further layer of thermal insulation material 58 to support a floor screed 59.

It is noted that one of the U-rails shown in Fig. 6 could be used to locate the support elements 13 in Fig. 1.

From the foregoing it will be appreciated that the I-shaped support elements 13 are part of permanent formwork that creates an integral upstand in a concrete raft which is cast in situ. The horizontal grooves 17 and 18 at the top and bottom of the support elements allow the connection with the H-rail and U-rail systems allowing the support elements to become integrated into the structure. Their I-shape allows the support elements to have good purchase in the U-rail or H-rail systems, adequate load spreading capacity on their top and bottom faces, and minimises the displacement of concrete so that the support elements become firmly locked into the concrete raft when the concrete -14 -pour is done. The arrangements described allow the wall upstand and the floor raft to be poured at the same time thus reducing the number of times and the associated cost of the concrete pumping or placement.

By including one or more holes in the support elements two supports could be joined together with a connector rod to use in pairs, e.g. when forming an internal wall.

Whilst the above description places emphasis on the areas which are believed to be new and addresses specific problems which have been identified, it is intended that the features disclosed herein may be used in any combination which is capable of providing a new and useful advance in the art.

Claims

-15 -CLAIMS1. Insulating concrete formwork: - a loadbearing structure (1); - a concrete slab (2) supported by the loadbearing structure; - an outer wall skin (10) of thermal insulation material; - an inner wall skin (12) of thermal insulation material which is spaced from the outer wall skin; - an intermediate concrete layer (28) between the inner and outer wall skins; wherein the inner wall skin (12) is supported on a plurality of mutually spaced support elements (13) interposed between the inner wall skin and the loadbearing structure (1) and wherein the intermediate concrete layer (28) is integrally formed with the concrete slab through gaps between the support elements (13).
2. Insulating concrete formwork according to claim 1 wherein each support element (13) is substantially I-shaped with a base member (14) and a top member (15) connected by an upright member (16).
3. Insulating concrete formwork according to claim 2 wherein the base member and the top member are substantially parallel.
4. Insulating concrete formwork according to claim 2 or 3 -16 -wherein the top members of the support elements are received in H-rails (20) which are in turn engaged with the inner wall skin.
5. Insulating concrete formwork according to claim 4 wherein inner faces of the H-rails have ribs (23) which engage in longitudinally extending grooves (17) formed in the top members of the support elements.
6. Insulating concrete formwork according to claim 4 or 5 wherein the H-rails are engaged with the outer wall skin by cross-ties (22).
7. Insulating concrete formwork according to claim 6 wherein the cross ties (22) engage H-rails (19) which are in turn engaged with the outer wall skin.
8. Insulating concrete formwork according to any of claims 2 to 7 wherein the base members (14) of the support elements (13) are received in U-rails (40) which are secured to the loadbearing structure (1).
9. Insulating concrete formwork according to claim 3 wherein inner faces of the U-rails have ribs (43) which engage in longitudinally extending grooves (18) formed in the base members of the support elements.
10. Insulating concrete formwork according to claim 8 or 9 wherein the U-rails are engaged with the outer wall skin (10) by -17 -cross-ties (22).
11. Insulating concrete formwork according to claim 10 wherein the cross ties engage U-rails (39) which receive the bottom of the outer wall skin (10).
12. Insulating concrete formwork according to any preceding claim wherein the support elements (13) are cast from concrete.
13. Insulating concrete formwork according to any preceding claim wherein the loadbearing structure (1) comprises a base layer of thermal insulation material which supports the concrete slab (2).
14. Insulating concrete formwork according to claim 13 wherein the loadbearing structure (1) supports closer blocks (4) which are spaced from the outer wall skin (10) by a concrete foundation strip (52).
15. Insulating concrete formwork according to claim 14 wherein the outer wall skin is formed with apertures (47) and wherein the concrete foundation strip (52) is integrally formed with the concrete slab (2) through said apertures.
16. Insulating concrete formwork according to claim 14 or wherein the concrete foundation strip (52) supports a hard wall facing (56).
-18 - 17. Insulating concrete formwork according to claim 16 wherein a layer of structural thermal insulation material (55) is interposed between the concrete foundation strip (52) and the hard wall facing.
18. A method of constructing insulating concrete formwork: - providing a loadbearing structure (1); - providing a concrete slab (2) supported by the loadbearing structure; - providing an outer wall skin (10) of thermal insulation material; - providing an inner wall skin (12) of thermal insulation material which is spaced from the outer wall skin; - providing an intermediate concrete layer (28) between the inner and outer wall skins; wherein the inner wall skin (12) is supported on a plurality of mutually spaced support elements (13) interposed between the inner wall skin and the loadbearing structure (1) and wherein the intermediate concrete layer (28) is integrally formed with the concrete slab (2) through gaps between the support elements (13).
19. A method of constructing insulating concrete formwork according to claim 18 which includes providing support elements (13) which are each substantially I-shaped with a base member (14) and a top member (15) connected by an upright member (16).
-19 - 20. A method of constructing insulating concrete formwork according to claim 19 which includes providing support elements (13) in which the base member and the top member are substantially parallel.
21. A method of constructing insulating concrete formwork according to claim 18, 19 or 20 which includes providing a loadbearing structure (1) comprising a base layer of thermal insulation material which supports the concrete slab (2).
22. A method of constructing insulating concrete formwork according to claim 21 which includes providing on the base layer (1) closer blocks (4) which are spaced from the outer wall skin (10) by a concrete foundation strip (52).
23. A method of constructing insulating concrete formwork according to claim 22 which includes providing the outer wall skin with apertures (47) and integrally forming the concrete foundation strip (52) with the concrete slab (1) through said apertures.
24. A method of constructing insulating concrete formwork according to claim 22 or 23 which includes providing a hard wall facing (56) supported on the concrete foundation strip (52).
25. A method of constructing insulating concrete formwork according to claim 24 which includes providing a layer of structural thermal insulation material (55) between the concrete foundation -20 -strip (52) and the hard wall facing.