GB2249569A

GB2249569A - Concrete roofing system

Info

Publication number: GB2249569A
Application number: GB9123559A
Authority: GB
Inventors: Ian Colin Bell
Original assignee: Individual
Current assignee: Individual
Priority date: 1990-11-06
Filing date: 1991-11-06
Publication date: 1992-05-13
Anticipated expiration: 2011-11-06
Also published as: GB9024077D0; GB9123559D0; GB2249569B

Abstract

There is described a concrete roofing system which comprises: one or more concrete beam 9 capable of forming a base framework for a roof; and a plurality of concrete filler blocks 10 capable of being supported by the concrete beam framework so as to form a roof structure for a building. The blocks 10 may be grooved for the mounting of tiles or slates 19. <IMAGE>

Description

CONCRETE BUILDING SYSTEM This invention relates to a building system, in particular to a concrete roofing system.

The process of "simple building", particularly in the United Kingdom, has become unnecessarily complicated, wasteful and expensive, as a great variety of materials is used on a typical building project.

Even on the simplest of buildings, such as a single storey dwelling, a vast array of often incompatible materials are used, all having to be joined or set close together with different specialists responsible for the various areas of work. Many of the materials used involve long manufacturing processes, for example steel and plastics. Although the natural product wood is still used, its increasing cost and its deterioration in temperate climates has meant that simple sawn untreated timber is rarely used. All structural timber has to be treated to improve its damp resistance and prefabrication of timber components is becoming more frequent.

There is therefore a need to simplify the building processes which have developed over the years.

Concrete has been widely used in southern Europe as a building material, even as a structural roofing material. The concrete has always, however, been mixed on site and there has been limited or no prefabrication of structural concrete roofing elements. The concrete mixed on site has limited insulation properties and is very heavy. Its use is resticted to countries with warmer climates and less stringent building standards.

The present invention meets the needs of the building industry by combining the simplicity of traditional methods of building in less developed countries with modern production techniques.

According to the present invention there is provided a concrete roofing system which comprises: one or more concrete beam capable of forming a base framework for a roof; and a plurality of concrete filler blocks capable of being supported by the concrete beam framework so as to form a roof structure for a building.

Both the concrete beams and concrete filler blocks are preferably pre-fabricated components.

Preferably the concrete used for both components is a lightweight aggregate concrete. By the term concrete is meant a mixture of cement, coarse and/or fine aggregate and water. The proportions may be varied to vary the properties of strength and durability of the resulting concrete. Normal weight concrete, using naturally occurring aggregates, has an average density of approximately 2400 kg/m3.

Lightweight aggregates are produced artificially by processing certain natural materials or by-products of other industries. When these materials are combined with cement, water and optionally also natural aggregates, concrete with a density ranging between 1600 kg/m3 to 1900 kg/m3 can be produced. The processed natural materials include clay, shale and slate and the industrial by-products include pulverised fuel ash and blast furnace slag. The process used to manufacture such aggregates may comprise heating the basic material to high temperatures (up to 1200"C) to bring about its expansion or agglomeration. Expansion may be caused by gases or steam being driven off during the heating process while agglomeration may be caused by burning off various compounds followed by the melting and fusing together of the basic material.All lightweight aggregates formed in this way contain internal air voids or pores which greatly influence the resulting concrete water absorption and strength and bring about its insulating qualities. A lightweight aggregate concrete which is preferred for use in the present invention is air entrained lightweight aggregate concrete which has gas pockets trapped within the concrete matrix reducing its density and strength but increasing its thermal insulation properties. The gas may be introduced into the concrete by a variety of means, including its introduction into the mixing process and using air entraining or foaming agents. A particularly preferred lightweight aggregate concrete is aerated reinforced concrete, known as ARC. ARC is lightweight, fire retardant and a good thermal insulator.Foamed concrete, although suitable for use in the present invention, is not as preferred, as it has a more limited strength and is, therefore, less suited for structural applications.

The concrete beams, which are to support the concrete filler blocks, may be made of a different, and stronger, concrete than that of the filler blocks. The concrete beams could, for example, be made from conventional normal weight concrete or a lightweight concrete, and the concrete filler blocks could be formed from ARC or foamed concrete. The concrete beams are preferably made of a lightweight reinforced concrete. The filler blocks are preferably made of an aerated lightweight concrete.

Both the concrete beams and the filler blocks are preferably reinforced. Such reinforcement could take any conventional form, for example reinforcement could be by the use of bars and/or mesh of a metallic material.

The concrete beams are able to form a base framework by spanning across the space where the roof is to be formed. The framework formed from the concrete beams will determine the shape of the roof to be formed. The roofing system of the present invention may be used for the building of either flat roofs or more traditional pitched roofs. For a pitched roof the beams may span in a substantially vertical direction or, and more preferably, in a substantially horizontal direction. The concrete beams may be supported on the external walls of the building on which the roof is to be formed as well as on either (a) internal walls carried up from the floor or floors below into the roof space, or (b) divider walls formed within the roof space and supported on a ceiling.The ceiling with case b) above should be strong enough to support the load of the divider walls, and is preferably, therefore, constructed of concrete. The roofing system could, for example, be supported on a ceiling of a concrete block and beam system of the same sort as that which is currently used for structural floors.

If the concrete beam spans in a substantially vertical direction it may be necessary for special attachment means to be provided for the support of the filler blocks.

The concrete beam must be able to support at least one filler block. Preferably each filler block is supported at one end by one concrete beam and at its other end by another concrete beam. The concrete beam may be provided with a shape capable of providing support on the underside of the filler block (when in use) only. Preferably, however, each concrete beam is shaped so as to provide both support underneath the filler block as well as lateral restraint. For this latter purpose each concrete beam is preferably provided with a shoulder on which the filler block can be supported. The height of the shoulder is preferably substantially equal to the height of the filler block.

In order for the concrete beam to be light enough for the entire roof structure to be constructed by a minimum of two people, the length of the beams, and therefore the distance over which they are able to span, is limited. Each beam may, therefore, be provided with means for linking it to another beam to increase the possible span distance. Such means for allowing the'joining of two or more beams together may take any suitable form, for example stainless steel straps, prefabricated galvanised mild steel sleeves used with connector plates and bolts, or the provision of a cast-in threaded socket in the beam which is able to cooperate with a double-threaded "turnbuckle" or equivalent having opposite threads so as to be able to connect two beams together.

The filler blocks should be of such a shape that when arranged together, supported on the base framework of concrete beams, they form a solid roofing structure.

Shapes which are able to tessellate are therefore preferred for the filler blocks. The filler block may be fixed in position by mechanical fixing means or by cementitious grout.

The filler blocks are preferably adapted to allow the mounting of roof tiles or slates on the roof structure when assembled. For this purpose the filler blocks are preferably provided on their external surface (when in an assembled roof structure) with recesses or grooves, capable of receiving corresponding projections on the roof tiles or slates to be used.

The grooves may be continuous across the filler block, in a substantially horizontal direction. Each filler block may be provided with one or more groove or recess. Each filler block is preferably provided with a plurality of continuous grooves lying parallel with each other so that each filler block has a castellated profile. The filler blocks are then preferably arranged in the roof structure so that the castellated profile is continuous and uninterrupted across the entire roof structure. The roof tiles may be simply placed on top of the filler blocks with a part thereof being accommodated in the recess or groove or alternatively battens, for example made of treated softwood, could be inserted within the grooves or recesses to allow for the fixing of the tiles or slates thereto by conventional means such as nails.

Traditional slates or tiles may be used in association with the roofing system as well as concrete tiles.

The conventional use of felt for roof structures is not required with the roofing system of the present application. When felt is not used, however, moisture may penetrate the roof covering. In order to allow any such moisture to drain away from the roof structure to the eaves, drainage means may be provided in either or both of the filler blocks or concrete beams. A continuous drainage slot or channel could, for example, be provided in either of the components. Drainage holes would also be suitable.

Both the filler blocks and concrete beams could be prefabricated to various sizes to suit varying building systems.

Conventionally used ridge and/or hip tiles could be fixed to the roof structure formed from the roofing system of the present invention, and no special adaptation of those elements is required, although the system can be easily adapted if desired, for example for use with a hipped roof, as is described below.

Although it is not a necessity, the roofing system of the present invention is preferably used in combination with a building provided with concrete floors. Although the roofing system of the present invention is heavier than a traditional roofing system, the additional load on the building foundations is small, as the substantial load on the foundations is due to the floors and walls of the building. The loads from the roofing system, in particular the lateral force from the filler blocks on to the beams when in use, is carried to the eaves and thereby to the walls of the building and to a precast concrete ceiling if present.

The roofing system of the present invention may be used on single or two storey buildings, for multidwelling buildings and for both domestic and commercial buildings.

The roofing system has been found to meet the requirements of structural stability and strength required in the building industry, and yet is sufficiently light to be installed by a minimum or two people.

According to a second aspect of the present invention there is provided a concrete beam for use in the roofing system of the first aspect of the present invention.

According to a third aspect of the present invention there is provided a concrete filler block for use in the roofing system of the first aspect of the present invention.

The present invention is advantageous as allows the use of building materials of uniform high quality, performance and durability, which are compatible with each other, and which reduce both costs and complexity on site. The materials used for the roofing system are derived in the main from those found in the ground, i.e. clays and aggregates, and the processes required to extract them are relatively low technology.

Concrete is also an inherently good sound insulator and is also very good at resisting fire spread. Use of the roofing system of the present invention would eliminate the need for the following common roofing products used in conventional roofing systems: structural timber, roofing felt, wind bracing, and in certain circumstances fibre quilt roof space insulation. Its use would also allow the simplification of conventional eaves and flashings. The roofing system also allows for utilisation of the roof space. It is a particularly flexible system which would be easy to convert, for example if additional living space were required in the roof space. This is because the filler blocks would be easy to remove for replacement with, for example, windows or solar panels.The roofing system would, when compared with conventional roofing systems, improve thermal insulation, sound insulation and fire resistance. It would also have a longer useful life, as no timber treatment would be required, and would involve lower maintenance costs. In general terms the roofing system would lead to less wastage of material on site, less variety of labour needed for installation, to a more thermally efficient and thereby to a more energy efficient structure, and to one requiring less maintenance. Moreover, the roof structure formed by the roofing system is able to take all conventional, standard roof finishes and can be adapted to suit any necessary apertures, pitches, abutments, hips, gables etc.

For a better understanding of the present invention, and to show how the same may be put into effect, reference will now be made, for the purposes of illustration only, to the accompanying drawings in which: Figure 1 is a cross-section through a side elevation of one embodiment of the roofing system of the present application in situ in a schematically shown building; Figure 2 is a partially exposed perspective view of another embodiment of the roofing system in situ; Figure 3 is a) a plan view, b) an underplan view, c) a cross-section along lines A-A of a) and d) a cross-section along lines B-B of a) of one embodiment of a filler block according to the present invention; Figure 4 is a) a plan view, b) a side elevational view, c) an underplan view, and d) a cross-section along lines A-A of a) of one embodiment of a concrete beam according to the present invention;; Figure 5 is a schematic cross-section of a side elevational view of a roofing system of the present invention in place; Figure 6 shows a) a side elevational view, b) a cross-sectional view along A-A of a) and c) a crosssectional view along line B-B of a) of two beams joined together in a first manner; Figure 7 shows two beams according to the present invention joined together in a second manner; Figure 8 is a partially exposed perspective view of a gabled roof using a roofing system of the present invention; Figure 9 is a partially exposed perspective view of a hipped roof using a roofing system of the present invention; and Figure 10 is a schematic perspective view of a roofing system according to the present invention adapted for use in a hipped roof.

The schematic building shown in Figure 1 comprises foundations 1 on which an external side wall 2 is built, from which wall 2 extend ground floor 3 and first floor 4. Above a multi component ceiling system 5 is a roof structure 6 according to the present invention, above which a system of roof tiles 7 topped with a conventional ridge tile 8 is arranged.

The roof structure 6 comprises a plurality of concrete beams 9 extending in a substantially horizontal direction and a plurality of filler blocks 10 which are supported on the beams 9.

As can best be seen from Figure 4, in the embodiment shown the beams are provided with two shoulders lla and llb, which extend along the entire length of the beam 9 to give them an overall T-shape.

Each beam 9 is of such dimensions that a steel reinforcing bar 12 can be inserted to reinforce the strength of the beam 9. Each beam has a maximum length of around 4m, e.g approximately 3.75 metres, with a standard length of 3m being preferred. When lengths towards the upper limit of this range are used it is desirable to use the roofing system in conjunction with a building having concrete floors as well as having walls built up into the roofing space.

In the embodiment shown in Figures 2, 3 and 5, the filler blocks, which span the distance between parallel extending beams 9 (see Figure 2), are rectangular in overall shape (see Figure 3b) and are provided with a series of parallel running grooves 13 which give the filler block an overall castellated appearance. Each end of a filler block 10 is supported in use on one of the shoulders lla,b of the beam 9. The width of the projections 14 of the filler block 10 between the parallel grooves 13 is chosen to match the width of the part of the beam 9 which extends between adjacent filler blocks 10 so as to provide a uniform spacing of grooves over the entire roof structure.

As can best be seen from Figure 2, the parallel extending concrete beams 9 are supported by an internal blockwork dividing support wall 15 and at the eaves are also supported by, in the embodiment shown, concrete ceiling beams 16. Traditional eaves 17, gutters 18 and tiles 19 may be arranged around the roof structure 6.

Projections 20 on the underside of the tiles 19 sit within the parallel extending grooves 13 of the filler blocks 10.

The lateral load of the filler blocks 10 on the beams 9 can be transmitted to the ceiling and walls of the building by means of a specially adapted end block 21 as can be seen in Figure 5 in which the roof is set at a pitch of 30 .

In the alternative embodiment shown in Figure 1 the filler blocks 10 have a continuous smooth upper surface 22 and the beams 9 extend above that upper surface. The tiles 19 are hooked over the projecting ceiling beams 9 by means of a projecting member 23.

So that the beams are easily transportable and the entire roof system 6 is able to be erected by a minimum of two people the length of the beam is kept to around 3 metres. Beams may be joined together by means, for example of the cover plates 24 shown in Figure 6 which are attached to the beam 9 by means of bolts 25 which pass into cast sleeves embedded in the beam 26a and b.

Alternatively, as shown in Figure 7, threaded sleeves 27a,b provided in the beams 9 can cooperate with a double threaded turnbuckle 28.

In Figure 8 is shown a roofing system according to the present invention in use for a gable-ended roof.

In Figure 9 is shown a roofing system according to the present invention in use for a hipped roof.

Figure 10 shows in more detail how the roofing system may be adpated for use in a hipped roof. Pairs of concrete beams (29a,b and 30a,b) are used as cantilevers projecting perpendicularly outwards from the support walls (31a,b). Each pair meet at the desired angle, for example at a right angle, and are joined together by a joint piece (32 and 33), which may be of metal. Filler blocks (not shown) can be positioned so as to span between the beams (29a,b and 30a,b) to form the roof structure. An additional support wall under the cantilever beams is not an essential requirement. The shape of the beams is not shown in detail in Figure 10 for the purposes of simplification.

Claims

1. A concrete roofing system which comprises: one or more concrete beam capable of forming a base framework for a roof; and a plurality of concrete filler blocks capable of being supported by the concrete beam framework so as to form a roof structure for a building.

2. A roofing system according to claim 1, wherein either or both the concrete beam and the concrete filler blocks are pre-fabricated components.

3. A roofing system according to claim 1 or 2, wherein both components are formed from a lightweight aggregate concrete.

4. A roofing system according to claim 3, wherein each concrete beam is made of a lightweight reinforced concrete.

5. A roofing system according to claim 3 or 4, wherein the filler blocks are made of an aerated lightweight concrete.

6. A roofing system according to any preceding claim, wherein in use the or each beam spans in a substantially horizontal direction.

7. A roofing system according to any preceding claim, wherein, in use, the or each concrete beam is supported on an external wall of a building on which the roof is to be formed as well as on either (a) an internal wall carried up from the floor or floors below into the roof space, or (b) a divider wall formed within the roof space and supported on a ceiling.

8. A roofing system according to any preceding claim, wherein each concrete beam is provided with a shoulder on which a filler block can be supported.

9. A roofing system according to claim 8, wherein the height of the shoulder is substantially equal to the height of the filler block.

10. A roofing system according to any preceding claim, wherein the or each beam is provided with means for linking it to another beam.

11. A roofing system according to any preceding claim, wherein the filler blocks are adapted to allow the mounting of roof tiles or slates on the roof structure when assembled.

12. A roofing system according to claim 11, wherein the filler blocks are provided with recesses or grooves, capable of receiving corresponding projections on the roof tiles or slates to be used.

13. A roofing system according to claim 12, wherein each filler block is provided with a plurality of continuous grooves lying parallel with each other.

14. A roofing system according to claim 13, wherein the grooves are of such a shape that each filler block has a castellated profile.

15. A roofing system according to any preceding claim, wherein drainage means are provided in either or both of the filler blocks or concrete beams.

16. A concrete beam adapted for use in a roofing system according to any one of claims 1 to 15.

17. A concrete filler block adapted for use in a roofing system according to any one of claims 1 to 15.

18. A roofing system substantially as hereinbefore described with reference to, and as illustrated in, Figure 1; Figures 2, 3, 4 and 5; Figure 6 or Figure 7 of the accompanying drawings.