GB1605136A

GB1605136A - Collapsible structure and method of building using such a structure

Info

Publication number: GB1605136A
Application number: GB33619/77A
Authority: GB
Original assignee: APPLIED SURFACES Ltd
Current assignee: APPLIED SURFACES Ltd
Priority date: 1977-08-10
Filing date: 1977-08-10
Publication date: 1982-02-10
Also published as: DE2834496A1; FR2400098A1; FR2400098B1

Description

(54) COLLAPSIBLE STRUCTURE AND METHOD OF BUILDING USING SUCH A STRUCTURE (71) We, APPLED SURFACES LTD., a British Company of 8, St. Georges Street, Douglas, Isle of Man, do hereby declare this invention, for which we pray that a Patent may be granted to us and the method by which it is to be performed to be particularly described in and by the following statement: This invention relates to a collapsible structure which can be suitable for use in building construction.

With present day building methods, and in particular the provision of concrete floors on the ground floors of houses, considerable trouble has occurred where such floors are laid onto subsoils which are predominantly of a clay nature. The problem which arises depends upon the fact that clay will swell when moisture is introduced and will shrink when moisture is removed. In the case of clay situated under a house, the difference in level between dry clay and wet clay can be as high as 30 mm.

Thus, variations in the condition of the clay can have a very serious effect on any flooring material which is laid directly thereon, and when this flooring material is in contact with walls, the variations can cause severe damage to the building to which it belongs. In fact, this damage can be so severe that the building has to be demolished as being uneconomical to repair.

In order to overcome this problem it has been proposed to provide precast floor elements which can be mounted in position leaving a void between the underside and the ground. However, this process is of a very costly nature because, in most instances, it necessitates the transport of large concrete blocks and the provision at the site of a relatively large crane in order to unload the concrete elements and to place them in their appropriate position. As a result, other means have been tried to introduce between the floor and the clay a material which is sufficiently compressible to allow the movement of the clay to take place but of sufficient strength to form a firm base for the casting of the appropriate floor. Such proposals have included expanded polystyrene, ash and uncompacted sand.However, these have not proved satisfactory since where they are strong enough to support the load during casting of a concrete floor, they are insufficiently compressible to to allow for full expansion and contraction of the clay and vice versa.

The present invention seeks to provide a structure which is generally rigid initially but which can be caused to collapse under certain conditions.

According to the invention, there is provided a collapsible structure which is rigid when dry and collapsible when wet comprising a first imperforate sheet of material, a second sheet of material having open perforations therein to permit the passage of moisture and a separating structure of poor wet strength and of greater thickness than the sheets, the separating structure being sandwiched between the sheets to provide an otherwise hollow space therebetween.

Preferably the separating structure is of honeycomb form and comprises water soluble or water disintegratable paper. Both sheets may comprise hardboard. The whole may suitably be glued together using a water soluble glue.

A method of building using such a structure is described and claimed in our copending Application No. 5016/81 (Serial No. 1605137).

The invention will now be described in greater detail, by way of example with reference to the drawing, the single figure of which is a perspective view of a corner of a board having a collapsible structure, partly cut away.

Referring to the drawing, the collapsible board 1 comprises two outer skins or sheets 2 and 3 of hardboard, the skin 2 intended to be in the upper position being unbroken. The underneath skin 3 is provided with a number of perforations 4. Between the two skins there is arranged a honeycomb structure 5 of a water soluble paper, e.g. reconstituted paper, which in the form shown has a hexagonal honeycomb construction.

In use in building construction, when the ground has been prepared and the foundations laid, the boards are laid with their perforated face downwardly on the clay surface and the top of the board is covered by suitable damp proof membrane, for example polythene. Once in position, the floor can be cast thereon in the usual fashion for reinforced concrete and compacted in the usual way.

With suitable dimensions of the board, even when the clay is very wet, the board will remain firm during the period which is ncessary to set the concrete, i.e. a period in excess of sixteen hours. At the end of this period, the moisture from the clay seeps through the perforations 4 in the skin 3 and causes disolution of the glue and disintegration of the honeycomb structure.

Thus with any swelling of the clay, the skin 3 can be pushed upward with virtually no resistance until it reaches the skin 2, thus providing ample room for expansion of the clay. It is necessary for the thickness of the boards to be of the order of 30 mm since this is normally considered the maximum expansion of clay but for safety factor reasons it may be somewhat larger. It is to be noted that there is no need for the edges of the board to be closed and in fact such closure would be detrimental to the compressibility of the board.

It is to be understood that various modifications may be made to the above described embodiment without departing from the scope of the invention. For example the honeycomb structure which has been provided may be replaced by other forms of honeycomb structure or indeed could be replaced by longitudinal webs. The arrangement of the apertures in the skin could be different to that shown and in fact larger and less numerous apertures could be used. While water soluble paper and glue are preferred, it would be possible to use as a honeycomb structure a material having a low wet strength and to rely on the destruction of the honeycomb without the necessity of arranging for it to become unglued.However, it is pointed out that this modification is less desirable than the use of water soluble materials since the use of the water soluble material will provide for a better certainty of early compressibility. If desired, in certain circumstances the hardboard used for the skins could be re placed by other suitable materials, such as plastics sheet.

WHAT WE CLAIM IS: 1. A collapsible structure which is rigid when dry and collapsible when wet comprising a first imperforate sheet of material, a second sheet of material having open perforations therein to permit the passage of moisture and a separating structure of poor wet strength and of greater thickness than the sheets, the separating structure being sandwiched between the sheets to provide an otherwise hollow space therebetween.

2. A structure as claimed in Claim 1, wherein the separating structure is of honeycomb form.

3. A structure as claimed in Claim 1 or 2, wherein the separating structure comprises water soluble or water disintegratable paper.

4. A structure as claimed in any one of Claims 1 to 3, wherein the sheets of material comprise hardboard.

5. A structure as claimed in any one of Claims 1 to 4, wherein the structure is assembled with a water soluble glue.

6. A collapsible structure substantially as described herein with reference to the drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. the concrete, i.e. a period in excess of sixteen hours. At the end of this period, the moisture from the clay seeps through the perforations 4 in the skin 3 and causes disolution of the glue and disintegration of the honeycomb structure. Thus with any swelling of the clay, the skin 3 can be pushed upward with virtually no resistance until it reaches the skin 2, thus providing ample room for expansion of the clay. It is necessary for the thickness of the boards to be of the order of 30 mm since this is normally considered the maximum expansion of clay but for safety factor reasons it may be somewhat larger. It is to be noted that there is no need for the edges of the board to be closed and in fact such closure would be detrimental to the compressibility of the board. It is to be understood that various modifications may be made to the above described embodiment without departing from the scope of the invention. For example the honeycomb structure which has been provided may be replaced by other forms of honeycomb structure or indeed could be replaced by longitudinal webs. The arrangement of the apertures in the skin could be different to that shown and in fact larger and less numerous apertures could be used. While water soluble paper and glue are preferred, it would be possible to use as a honeycomb structure a material having a low wet strength and to rely on the destruction of the honeycomb without the necessity of arranging for it to become unglued.However, it is pointed out that this modification is less desirable than the use of water soluble materials since the use of the water soluble material will provide for a better certainty of early compressibility. If desired, in certain circumstances the hardboard used for the skins could be re placed by other suitable materials, such as plastics sheet. WHAT WE CLAIM IS:

1. A collapsible structure which is rigid when dry and collapsible when wet comprising a first imperforate sheet of material, a second sheet of material having open perforations therein to permit the passage of moisture and a separating structure of poor wet strength and of greater thickness than the sheets, the separating structure being sandwiched between the sheets to provide an otherwise hollow space therebetween.