GB2562492A

GB2562492A - Moisture-retarding weathering protection feature for inclusion in construction sandwich panels

Info

Publication number: GB2562492A
Application number: GB1707813.0A
Authority: GB
Inventors: Joseph Reidy John; Dennany Austin; Matthew Reidy John
Original assignee: Thermo Precast Ltd
Current assignee: Thermo Precast Ltd
Priority date: 2017-05-16
Filing date: 2017-05-16
Publication date: 2018-11-21
Also published as: GB201707813D0

Abstract

A void-former for the installation of flashing 4 in construction sandwich panels comprises a planar element 1 having a U-shaped cavity 2 at one end and a plate 3 at the other end. The plate extends perpendicularly above and below the planar element in use. The planar element traverses a central cavity of the sandwich panel, with the plate positioned on the inner surface of the inner leaf 7 of the panel. The void-former thus provides a recess in the outer face of a precast panel above an abutting structure 10 for the insertion of flashing for weather protection. The void-former may span the width of the panel, and the planar element may be attachable to the inner leaf by screws, nails or adhesive. The panel may be formed from pre-cast concrete. The void-former may be formed by extrusion from a plastics material such as PVC.

Description

(54) Title of the Invention: Moisture-retarding weathering protection feature for inclusion in construction sandwich panels

Abstract Title: Void-former for the installation of flashing in sandwich panels (57) A void-former for the installation of flashing 4 in construction sandwich panels comprises a planar element 1 having a U-shaped cavity 2 at one end and a plate 3 at the other end. The plate extends perpendicularly above and below the planar element in use. The planar element traverses a central cavity of the sandwich panel, with the plate positioned on the inner surface of the inner leaf 7 of the panel. The void-former thus provides a recess in the outer face of a precast panel above an abutting structure 10 for the insertion of flashing for weather protection. The voidformer may span the width of the panel, and the planar element may be attachable to the inner leaf by screws, nails or adhesive. The panel may be formed from pre-cast concrete. The void-former may be formed by extrusion from a plastics material such as PVC.

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Figure 1.

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Figure 2

Title

Moisture-retarding weathering protection feature for inclusion in construction sandwich panels.

Field of the Invention

The present invention relates to a void-former suitable for providing a weathering protection detail for construction sandwich panels, such as for example precast concrete sandwich panels, at abutment details or joints, and which also facilitates insertion of flashing.

Background to the Invention

Sandwich construction panels are used for the rapid construction of buildings. A sandwich panel is a construction panel consisting of an inner leaf, a central section of insulation, and an outer leaf. Said leaves can be connected by horizontal wall ties, made of suitable materials such as steel or plastics material, or other materials wellknown in the art. The inner and outer leaves of a construction sandwich panel can be constructed of, for example, concrete.

The use of precast concrete sandwich panels for house construction is not a new idea. However, the use of such panels in the past gave rise to significant weathering problems, both at joints and at abutment details. Moisture ingress at abutments is a problem that must be considered with all types of construction as it can give rise to structural problems. An external wall can become an internal wall below the level of an abutting feature, and thus adequate weathering protection is highly desirable at such locations, to prevent penetration of moisture to the inside of the building.

In masonry construction, a stepped damp-proof course or tray can be provided. Catchment trays, typically provided with weepholes, can be built into blockwork, to safely discharge any accumulated water on to the roof slope. Such features are stepped to follow the lines of the bed joints and can be constructed in lead or pressed aluminium.

However, in construction with pre-cast concrete sandwich panels, the walls have no bed joints and consequently a stepped damp-proof course cannot be provided. Another well-known solution to the weathering problem at abutments and joints is the use of flashing and / or a damp proof course; both of which can prevent or greatly impede ingress of moisture to a building. Flashing can be of any suitable material, for example, lead, aluminium or plastics material. On traditional brick-wall buildings, flashing can be readily introduced to the structure during construction and / or extension of existing structures, by removing areas of mortar or bricks themselves. In contrast, buildings constructed from precast concrete sandwich panels do not typically lend themselves to convenient installation of flashing; the panels do not contain a suitably formed recess into which such flashing could be placed. Although a recess could be chiselled out, this is a tedious, and time consuming process requiring great care. Furthermore, when chiselling, the form of the recess produced may not be ideal. One solution would be to place a straight holder for flashing in the outer leaf of the sandwich panel, such as a conventional reglet-type structure; however, such a holder would need to be firmly and durably anchored within the sandwich panel, to ensure robustness. A further problem with such a conventional holder for flashing or reglettype structure when used in the context of a concrete sandwich panel would be the risk posed by moisture that could pass through the outer leaf of the concrete sandwich panel, for example via a crack, service opening or exposed area of concrete. In such a case, moisture on the inside face of the outer leaf of such a concrete sandwich panel would then run down unimpeded behind such a holder or reglet-type structure and would manifest on finishes internally below. Such moisture ingress following installation of such conventional structures, for example at abutments, windows, changes of roof level, is a known problem often encountered the construction industry. Thus, a problem to be solved is to form a waterproof recess in an outer face of a concrete sandwich panel for convenient insertion of flashing at abutment details.

CN 101864829 relates a rainwater leakage prevention structure for precast concrete external wall panels. Polyethylene foam rods and waterproof glue are provided at joints and these joints are further protected from leakage of rainwater by rubber flashing. US3981108 relates a reglet channel having an apron depending from the outer edge of its upper flange down to the level of the outer edge of its lower flange to protect a sealing compound placed in a groove in the interior of the channel from the deleterious effects of rain and sunlight. After installation in a wall the reglet channel may be slit open along this groove to provide access to its interior for engagement of the retaining lip of the flashing.

Summary of the Invention

In one aspect, the present invention provides a void-former for use in the installation of flashing in a construction sandwich panel comprising a planar element having a generally U-shaped cavity at one end and a plate at the other end, the plate extending generally perpendicularly above and below the planar element, wherein the planar element is sized to traverse the central cavity of the sandwich panel and wherein the plate is attachable to the inner leaf of the panel.

Suitably the generally U-shaped cavity extends through the outer leaf of the panel, at least partially.

The outer and inner leaves of the panel relate to the in use position of the panel, such that the outer leaf is the one on the exterior of the building.

Suitably, the plate extends perpendicularly above and below the planar element, suitably at angles of between 80° and 100°, but it will be apparent to the skilled person that other angles would also be functional and accordingly such angles are included in the definition of generally perpendicular. Particularly preferred is an angle of 90°. Suitably the plate is attachable to the inner leaf of the panel by screws, nails, adhesive bonding or the like.

The construction sandwich panel may be for example a precast concrete sandwich panel.

The term generally U-shaped cavity, it is intended to include cavities with sloped inner surfaces, such as V-shapes. Suitably the generally U-shaped cavity is dimensioned to retain a sheet of flashing. The flashing may be fixed in the U-shaped cavity by any suitable means.

Preferably the void-former is made of a suitable water-impermeable rigid plastics material of construction-grade. Preferably, a suitable plastics material is constructiongrade polyvinyl chloride (PVC).

In a further aspect of the invention there is provided a preformed construction sandwich panel comprising a void-former as defined above. In one embodiment of the present invention, the preformed construction sandwich panel comprising a void-former is a preformed concrete sandwich panel. The panel may have a central insulating layer with an outer layer on either side.

In a still further aspect the invention provides a method of manufacturing the voidformer as defined above, wherein the method comprises plastic extrusion.

The invention disclosed in the current application provides a solution to the weathering problem by forming a recess for flashing at abutment joints in precast construction/concrete sandwich panels using a void-former that is positioned within the panel during the casting and assembly process, and which remains as an in situ liner in the finished panel. The material from which the void-former is made can be any suitable material capable of withstanding the expansion and heating of concrete during pouring/curing while also being significantly impermeable to the passage of moisture; preferably such materials comprise any suitable plastics material, most preferably the material comprises construction-grade polyvinyl chloride (PVC). Given that the planar element of the void-former traverses the central cavity of the panel, forming the voidformer from water-proof material additionally enables it to advantageously act as a damp-proof course. In contrast to construction details using conventional holders for flashing or reglet-type structures as discussed in the Background to the Invention, were moisture to pass through the outer leaf of a concrete panel in which the void-former of the present invention is installed, then any such moisture running down the inside face of the outer leaf would be caught on the planar element and would be forced back out through the outer leaf as the only permeable route. Therefore, the finishes internally below would be protected from moisture ingress. By constructing the planar element from a water-impermeable plastics material, such as PVC for example, some measure of protection is provided against falling damp, rising damp or other structural dampness. The void-former is generally U-shaped at one end to receive flashing and has a T-section back plate formed on the other end to allow fixing to the outside face of the inner concrete leaf. In elevation, the remain-in-place void-former can for example span the full width of the panel.

In a most preferred embodiment the void-former is made of PVC.

Brief Description of the Drawings

Embodiments of the invention will be described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 is a section through a concrete sandwich panel showing the void-former in place.

Figure 2 is; a perspective view of a concrete sandwich panel with a void-former into which flashing has been inserted.

Detailed Description of the Drawings

As shown in Figure 1 and Figure 2 the void former comprises a planar element (1) with a generally U-shaped cavity (2) at one end of the planar element; and a plate (3) at the other end of the planar element that extends perpendicularly above and below the planar element. In the embodiment shown in the figures, the plate extends above and below the planar element at or near a 90° angle with respect to the planar element. As shown Figure 2, the void former is engageable with flashing (4) which has one edge thereof inserted into the generally U-shaped cavity (2); counter flashing is also shown. The void-former may have stainless steel helical wall ties (5) placed into it during construction, such that the wall ties are positioned in the outer leaf of the concrete sandwich panel, as shown in Figure 2. The planar element (1) horizontally traverses an insulation block panel (6) of the sandwich panel. The plate (3) sits flush against the inner concrete leaf (7) of the panel in use. The generally U-shaped cavity (2) is positioned in the outer concrete leaf (8) of the panel such that the open end of the U is on the external surface of the panel. Wall ties (9) are present above and below the joint, providing additional structural support. An abutment feature (10), is shown in Figure 1 and Figure 2 as a traditional roof finish. A damp-proof course membrane is shown for illustrative purposes in the abuttment feature (10) in Figure 2.

Horizontal wall ties (9) are present in such sandwich panels, however, for ease of viewing these have been omitted from Figure 2.

Although concrete sandwich panels are shown in Figure 1 and Figure 2, the skilled person will readily appreciate that the present invention can be used with any suitable construction sandwich panel, for example, one in which the inner and outer leaves of the panel are made of a construction material other than concrete. An internal insulation layer may or may not be present.

The thickness of the inner leaf (7) as shown in the accompanying figures is about 80 centimetres, the thickness of the outer leaf (8) is about 80 centimetres, and the thickness of the inner insulation section (6) is about 140 centimetres. Clearly other thicknesses could suitably be employed.

Weathering protection provides resistance to moisture ingress, such as wind-driven rain.Flashing is a material placed at a joint in a building to prevent ingress of moisture. Typically, flashing can be of lead, aluminium, plastics material or other materials wellknown to the skilled person.

The generally U-shaped portion (2) of the void former excludes concrete during pouring I curing of the concrete panel, such that a lined groove is formed on the external face of the panel. The generally U-shaped portion is intended to provide a suitable holder for inserting and affixing flashing.

A weathering protection detail can be formed using the void-former, as shown in Figures 1 and 2. Suitably, the weathering protection detail is located at abutment details. The void-former comprises a planar element (1) having a generally U-shaped cavity (2) at one end and a plate (3) at the other end, the plate extending above and below the planar element perpendicularly thereto. The skilled person will appreciate that what is intended is that the plate is at a right-angle to the planar element or at approximately a right angle; thus elements angled between 80° and 100° with respect to the planar element, for example, would be included in this description. Stainless steel twisted rods shall be inserted through the void former prior to casting the outer leaf. These stainless steel twisted rods provide the void-former with vertical support within the panel, and also confer further structural fixity and robustness on the voidformer.

Preferably, one or both of the lips of the element forming the generally U-shaped cavity (2) branch from the planar element (1). For example, as shown in Figure 1 and Figure 2, the lower lip of the generally U-shaped cavity branches from the planar element (1), while the upper lip is formed by a section continuous with the planar element (1). It is not intended to exclude generally U-shaped cavities where at least one of the upper and lower lips forming the generally U-shaped cavity branch from the planar element. In section, the length of the void-former corresponds to approximately the combined thickness of the insulation panel (6) and the outer leaf (8) of the sandwich panel.

In section, the height of the plate (3) is less than the length of the planar element. In section, the height of the plate (3) is greater than the height of the U-shaped cavity element (2).

One advantage afforded by the plate (3) of the void-former is that it helps to anchor and retain the void-former in place, both during casting of the panel and after casting; for instance, once the weathering protection detail has been installed in the building of which the panel is a part. Thus, by anchoring the void-former integrally within the sandwich panel, the plate (3) and planar element (1) function to ensure correct alignment of the U-shaped cavity (2) and to ensure that the void-former remains fixed in place in the cast panel. Advantageously, the plate (3) can be anchored to the inner leaf (7) of the panel by any suitable means. Without limitation, such suitable means can include, for example, adhesive bonding or fixing with stainless steel screws. Advantageously, the planar element (1) links the generally U-shaped cavity to the plate (3) , and provides the option of installing helical steel wall ties in the outer leaf of the panel, by drilling through the section of the planar element to be located in the outer leaf, inserting the wall ties, and sealing. In an assembled weathering protection detail, the plate of the void-former (3) would also catch against the insulation panel and prevent slippage. Therefore, the plate (3) and planar element (1) increase the durability, reliability and fixity of the resulting weathering protection detail at sites of installation, especially at abutment details.

The generally U-shaped cavity can be dimensioned to retain flashing (4), for example a sheet of lead flashing.

The void-former is not intended to be removed from the precast panel. The void-former remains in place in the finished panel.

With an assembled weathering protection detail, rainwater, for example, would be diverted by flashing (4), which is installed in the recess (2). The rainwater would flow away from the joint formed between the abutting feature (10) and the outer leaf of the sandwich panel (8), flowing instead on to the rooftiles of the abutting feature, and proceeding to roof guttering. Structural supports of the abutting feature, such as purlins or wooden battens would be protected thereby from the damage of moisture ingress. The joint introduced into the outer wall (8) of the panel by the void-former is afforded weathering protection because the void-former is made of a water-impermeable material, such as PVC.

In addition to permitting insertion of flashing, by making the void-former from a waterimpermeable plastics material, the remain-in-place void-former may provide some measure of weathering protection to the sandwich panel also. An advantageous aspect of making a void-former from a water-impermeable plastics material that traverses both the outer leaf (8) and the insulation (6) is that the void-former can provide some measure of protection against rising damp, falling damp, or other structural dampness. The plate (3) of the void former spans the full width of the panel.

Advantageously, the plate can facilitate placement of the void former during assembly of the panel.

The planar element (1) of the void-former spans the full width of the panel.

The planar element (1) traverses the insulation (6) in a sandwich panel, such that the plane of the element (1) is perpendicular to the plane of the flat surface of the panel walls (7 and 8).

Preferably, the U-shaped cavity of the void-former spans the full width of the front surface of the outer leaf (8) of the panel, without gaps. It is however not intended to exclude the possibility that that the cavity could be positioned only over such features in the building which could benefit from weathering protection, which features may not necessarily span the full width of the panel, nor be continuous. In such a case, the lateral ends of the recess (2) could be sealed by adding a vertical upstand or wall along said ends and the vertical upstand could for example be joined to a vertical leg, set against the outside face of the inner leaf (7), and could continue through the insulation (6) to terminate flush with the outside face of the outer leaf (8). Similarly, there may be several void-formers positioned in one panel.

The planar element of the void-forming feature can, optionally, have stainless steel helical wall ties (5) placed into it at intervals along its length. The void-forming feature is then anchored by anchoring means to the outside face of the inner concrete leaf (7). By way of non-limiting example, such anchoring means could comprise an adhesive or fixing with stainless steel screws. Then, elements of the panel are arranged for casting; these can include insulation panels (6). Then concrete is cast into the mould. The voidformer is made from a strong, rigid material that can withstand the casting process, most preferably PVC. Similarly, the panel can be cast in any orientation, provided that concrete is excluded from the generally U-shaped cavity of the void-former during casting and that the T-section back plate is positioned on the inner surface of the inner leaf. Preferably, the inner and outer leaves of the panel are cast separately, with the inner leaf cast lying flat.

By way of example: the inner leaf (7) can be cast in the horizontal plane on a shuttering bed, or other suitable mould for casting concrete. In this orientation, the inner leaf must cure to a sufficient extent to enable the void-former to be placed by its generally Tshaped back plate on the outer face of the inner leaf. The back plate is fixed by fixing means to the outer face of the inner leaf. The void-former is then further fixed in place by insulation panelling, which is placed either side of it. The insulation panelling forms the central portion of the sandwich panel. The insulation can, for example, come in sheets that are cut to suit the dimensions of the panel. Such insulation sheets can be cut to facilitate placement on either side of the void former, when the inner leaf is lying in the horizontal plane. The insulation is drilled and wall ties are inserted into the inner leaf through the insulation. The void former is drilled at intervals along the portion of the planar element that protrudes above the insulation, but not in the U-shaped cavity, and helical ties (5) are placed through the drill-holes; a seal is placed at each penetration location. Alternatively, the insertion and sealing of such helical wall ties can occur prior to placing the void former in the mould. Concrete to form the outer leaf (8) is poured on both sides of the void-former. The insulation (6) forms the inner face of the outer leaf. Therefore, the helical wall ties (5) become located in the outer leaf of the cast panel. The outer leaf is formed by pouring in concrete up to the height of the void-former.

The position of the void-former can be arranged such that the recess that results in the cast panel will be located above an abutting feature (10), or joint, for provision of a weathering protection detail, allowing a clearance from the top of the abutting feature sufficient to allow effective insertion of flashing into the recess provided by the Ushaped cavity. The flashing used can be of any material suitable to achieve effective weathering protection; for example, lead flashing. The void-former can be arranged such that the recess that results in the cast panel will be located above structural features where it can provide for the construction of a weathering-protection detail. The void-former can be manufactured by plastic extrusion.

The words “comprises/comprising” and the words “having/including” when used herein with reference to the present invention are used to specify the presence of stated features, integers, steps or components but do not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination.

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Claims

1. A void-former for the installation of flashing in a construction sandwich panel comprising a planar element having a generally U-shaped cavity at one end and a plate at the other end, the plate extending generally perpendicularly above and below the planar element, wherein the planar element traverses the central cavity of the sandwich panel when in situ in the panel and wherein the plate is positionable on the inner surface of the wall of the inner leaf of the panel.

2. A void former as claimed in claim 1 wherein the plate extends above and below the planar element at an angle of between 80 and 100°.

3. A void former as claimed in claim 2 wherein the plate extends above and below the planar element at an angle of 90°.

4. A void-former as claimed in any preceding claim wherein the U-shape cavity extends through the outer leaf of the panel when positioned in a panel.

5. A void former as claimed in any preceding claim wherein the generally U-shaped cavity is dimensioned to retain a sheet of flashing.

6. A void former as claimed in any preceding claim wherein the void former is dying mentioned to span the full panel width.

7. A void former as claimed in any preceding claim wherein the lateral ends of the recess (2) are sealed by a vertical upstand or wall along said ends.

8. A void former as claimed any preceding claim wherein the planar element is attachable to the inner leaf of the panel, by screws, nails or adhesive.

9. A void-former as claimed in any preceding claim for inclusion in precast concrete panels during casting which is is made of a rigid water-impermeable plastics material.

10. A void former as claimed in claim 9 wherein the plastics material is a polyvinyl chloride (PVC) plastics material.

11. A preformed construction panel comprising at least one void-former as claimed in any preceding claim.

12. A method of manufacturing the void-former as claimed in claims 1 to 10 wherein

5 the method comprises plastic extrusion.

Intellectual

Property Office

Application No: GB 1707813.0 Examiner: Mr William Crowe