[0001] This invention relates to a method and apparatus for providing a foundation for a
building. The preferred embodiment provides a method and apparatus particularly suitable
for providing a foundation for a conservatory or similar extension to a domestic dwelling.
However, the invention is not limited to such applications and may be used under a
wide range of circumstances to provide a foundation for many different types of building.
[0002] It is well understood that a fundamental pre-cursor to the construction of many buildings,
including conservatory type extensions, is the provision of a foundation.
[0003] Traditionally, foundations have been provided by excavating a trench and back-filling
the trench with concrete to provide a surface upon which a bricklayer can set out
a brick or block wall which will form a support for the upper parts of the building.
Depending on site conditions, the excavated trench may need partially back-filling
with hardcore material and compacting, and shuttering may be required, prior to the
pouring of the concrete. This traditional process has a number of disadvantages that
are well recognised within the building trade. In particular, it is critically important
to the overall success of the building project that the brick or block work is set
out in precisely the correct position on the concrete foundation. The concrete foundation
itself gives insufficient guide as to the correct position of the brick or block work
and accordingly considerable care must be exercised by the bricklayer in setting out
his work.
[0004] The problem is particularly acute if a factory pre-formed building, for example a
conservatory, is to be erected on the base provided by the bricklayer. Small errors
in the positioning or angles of the walls can lead to considerable difficulties in
correctly fitting the pre-formed building. The necessary accuracy can only be obtained
by skilled craftsmen spending a considerable amount of time and effort in the correct
setting out of his work. This procedure is costly. The cost of the operation are further
increased by the fact that the initial concrete strip must be allowed to at least
partially cure before the bricklayer can start work. This will mean a delay of at
least 24 hours between laying the concrete and starting the brick or block work. As
a result, the construction of a suitable foundation for even a small conservatory
will involve visits to the site on at least two separate days.
[0005] I have now devised a method, and an apparatus for use in that method, that obviates
many of the disadvantages of traditional foundations as outlined above. The preferred
embodiment of the invention allows considerable reduction in the time necessary to
complete a foundation and removes the problem of inaccuracies in the setting out of
the foundation walls, as outlined above.
[0006] According to a first aspect of the present invention a method for providing a foundation
for a building comprises: pre-forming a shuttering set so that in transverse cross-section
the shuttering set defines a vertical leg for retaining concrete and a horizontal
leg that extends inwardly of the building from the top of the vertical leg so that
it is, in use, supported by the concrete retained by the vertical leg; positioning
the shuttering set at a use location; levelling the shuttering set; pouring the concrete
into the shuttering set to be at least partly retained by the vertical leg and to
underlie and provide support for the horizontal leg; allowing the concrete to at least
partially cure; and constructing a wall on the horizontal leg aligned with a guide
provided by the horizontal leg.
[0007] The guide can conveniently be the outer edge of the horizontal leg where it joins
the vertical leg.
[0008] In effect, the exact line to which the bricklayer is to work in constructing the
wall is defined in the preferred embodiment by the juncture between the horizontal
leg and the vertical leg. Because the shuttering set is pre-formed it can be shaped
to provide exactly the correct dimensions and angles for the required wall. All that
is required on site is that the shuttering set be correctly positioned and levelled
before the concrete is poured. The fact that the wall is constructed on a horizontal
leg of the shuttering set means that work on building the wall can commence at a relatively
early stage of the cure of the concrete.
[0009] In the preferred embodiment of the invention the shuttering set includes a second
vertical leg that extends upwardly from the inner edge of the horizontal leg to retain
concrete so that the finished surface of the concrete is above the level of the horizontal
leg. If desired, a second horizontal leg may extend inwardly of the building from
the top edge of the second vertical leg to provide a surface on which an inner leaf
of a cavity wall may be constructed. Again, the invention obviates the need for detailed
setting out by the bricklayer since the outer edge of the inner leaf of the wall may
be aligned with the outer edge of the second horizontal leg. In the alternative, the
first horizontal leg may be wide enough to accommodate both the inner and outer leaf
of the required wall. In these circumstances the inner leaf may be constructed at
a pre-determined spacing from the outer leaf or may be constructed utilising a second
guide provided by the shuttering set. The second guide may be, for example, a ridge
formed on the horizontal leg or may be the second vertical leg.
[0010] In accordance with a second aspect of the invention there is provided apparatus for
carrying out the method of the invention, the apparatus comprising a pre-formed shuttering
set that, in transverse cross-section, defines a vertical leg for retaining concrete
and a horizontal leg that extends inwardly of the building from the top of the vertical
leg.
[0011] The invention will be better understood from the following description of a preferred
embodiment thereof, given by way of example only, reference being had to the accompanying
drawings wherein:
Figure 1 shows schematically and in cross-section an embodiment of apparatus in accordance
with the present invention positioned for receipt of concrete;
Figure 2 is an enlarged perspective view of a portion of the shuttering set of the
embodiment of Figure 1;
Figure 3 illustrates a levelling device;
Figure 4 illustrates schematically in plan view a shuttering set prepared for the
receipt of concrete; and
Figure 5 is a front view of the arrangement of Figure 4.
[0012] Referring firstly to Figure 1 there is illustrated in schematic cross-section a typical
arrangement for a foundation utilising the method and apparatus of the present invention.
The ground 1 at the site where the foundation is required has been excavated to provide
a trench 2. Soil has been removed over the entire area of the proposed building to
provide a platform 3 to be covered with concrete at the same time as the trench 2
is filled. The exact dimensions of the trench will be determined in light of the soil
conditions and structural requirements for the building to be erected on the foundation.
[0013] In accordance with the present invention there is provided a shuttering set 4 that
is supported on a plurality of screw jacks 5 each of which has a sole plate 6 resting
on the floor 7 of the trench 2. The jacks 5 allows the shuttering set to be raised
and lowered and each jacking location for levelling purposes. The datum level for
the shuttering set may be established by any suitable means. In a typical use of the
present invention for the construction of a foundation for an extension to a building
the datum will generally be established by reference to the existing building by securing
the shuttering set to the building at a pre-determined position. Under these circumstances,
after the shuttering set has been secured to the building the jacks 5 will be positioned
and operated to level the entire shuttering set.
[0014] The shuttering set is shown in more detail in Figure 2. It will be seen to comprise
a first vertical leg 10, a horizontal leg 11 and a second vertical leg 12. In the
illustrated embodiment of the invention the legs are extrusions of suitable material,
for example aluminium, and the vertical legs 10 and 12 are formed from the same profile.
The vertical legs 10, 12 are formed with profiles interlocked with opposite lateral
edges of the horizontal leg 10. A stabilising bar 13 is secured to the horizontal
leg by suitable means, (for example bolts having their heads retained in slots 29
provided for the purpose on the underside of the horizontal leg 11), and extends across
the shuttering set to the opposite side thereof where it is joined to a corresponding
horizontal leg (not shown). Stabilising bars are positioned as necessary to give the
shuttering set adequate resistance to spreading. Preferably, one or more diagonal
bracing bars 14 (Figure 4) are also secured to the horizontal legs of the shuttering
set to ensure squareness.
[0015] If it is necessary for the concrete slab to be reinforced the required reinforcing
steel 15 can conveniently be supported by resting it on the stabilising bars 13. By
this means the steel can be positioned at an optimum location without the need for
any additional support. In the illustrated embodiment of the invention further stabilising
bars 16 are secured to a flange 17 of the upper leg 12 to provide additional stabilising
to the structure. Further steel reinforcing mesh 18 may be supported on the upper
stabilising bars 16 if desired.
[0016] The structure of the jacks 5 is shown in more detail in Figure 3. Each jack 5 consists
of a tube 19 supported on and secured to the sole plate 6 and furnished, at the upper
end thereof, with a threaded insert 20. A threaded rod 21 engages the threads of the
insert 20 and carries at its upper end a plate 22. The plate 22 is supported on a
nut 23 that engages the threaded rod 21. A second nut 24 is locked to the first nut
23 with a washer therebetween so that the rod 21 may be rotated relative to both the
plate 22 and the insert 20 by applying a spanner to the nut 24. By this means, the
shuttering may be raised or lowered at the location of each jack 5. It is envisaged
that a jack 5 will be provided at each change of direction of the shuttering set.
Accordingly, in the simple rectangular foundation illustrated in Figure 4 a jack 5
will be provided at each of the corners 25, 26. If necessary, depending on the length
of the sides and the structural rigidity of the materials used for the shuttering,
additional jacks may be required, for example at the mid-side location 27 illustrated
in Figure 4. When the jacks are located at corners the plate 22 is preferably shaped
to assist in forming the corner. For example, if the jack is located at a right-angle
corner such as at 25 and 26 the plate 22 is conveniently in the form of an L shape
having legs of equal length that extend along both of the adjacent horizontal legs
11 of the shuttering set. Preferably, as seen particularly in Figure 3, the plate
22 is located using grooves 28 provided by the material of the horizontal leg 11.
Suitable fastenings may be used to lock the horizontal legs 11 to the plates 22.
[0017] The basic arrangement of one horizontal and two vertical legs illustrated in Figure
3 may suffice for certain applications. However, for many applications it will be
desirable to add a further horizontal leg 30 to the upper end of the vertical leg
12 to extend inwardly of the building. Additionally, it may in many instances be desirable
to add a flexible skirt 31 to the outer side of the lower vertical leg 10. The flexible
skirt 31 will assist in containing concrete poured into the shuttering set. In the
typical configuration such as illustrated in Figure 1 the flexible skirt 31 will tend
to deform into engagement with the trench wall to inhibit upward flow of concrete
around the lower leg 10.
[0018] The corner abutment of adj acent shuttering lengths may be achieved by cutting the
abutting ends at an angle, e.g. 45 degrees on each to make a 90 degree abutment. Alternatively,
and more advantageously, however, the vertical legs may be cut to length to abut at
the corner whilst the horizontal leg of each shuttering length is cut shorter so at
to terminate short of the corner, creating an opening in the horizontal surface at
the corner. A corner piece is then fastened in place in the corner opening against
which the jacks engage. This has the advantage that different corner angles can easily
be achieve by simply use of different corner pieces which set the corner angle.
[0019] In use of the present invention a complete shuttering set is preformed, typically
in a factory environment. The pre-forming will consist of cutting the lengths of material
to size and assembling the various components. The components are then transported
to site for final assembly. On site only the joints need be formed and these joints
can be formed quickly and accurately because all the components needed have been pre-cut
and substantially pre-assembled before arrival on site. Once the shuttering set has
been fully assembled it is located in the required position. If it is used to form
the foundation of an extension to an existing building it will be secured to the wall
32 of the host building 33 using conventional fixings. Once the shuttering set has
been secured to the building the jacks 5 will be positioned and adjusted to level
the shuttering set. Using jacks of the type described above levelling is easily effected
by placing a suitable spanner on the upper nut 24 and rotating it to raise or lower
the support plate 22 associated with a particular jack.
[0020] Once the shuttering has been levelled and the concrete pour a damp-proof course may
be laid on the platform 3. Alternatively, if desired the damp-proof membrane may be
laid to cover the platform 3 and the trench 2 before location of the shuttering set.
In this alternative, once the damp-proof membrane has been installed and the shuttering
correctly positioned, concrete is poured into the shuttering. The concrete will fill
the trench 2. The initial flow of concrete will land on the sole plates 6 to hold
them in position and thereby prevent the entire shuttering from "floating" as the
concrete level rises. In practice, the concrete will be suitably compacted (for example
by vibration) to complete fill the shuttering up to the level of the top edge of the
upper vertical leg 12. As a result, the concrete will be contained at least in part
by the lower vertical leg 10 and the upper vertical leg 12 and the concrete will underlie
and support the horizontal legs 11 and 30. If desired, holes may be provided through
the horizontal legs 11 and/or 30 to vent any air pockets that may be formed during
concrete compaction. The skirt 31 will prevent excessive flow of concrete upwardly
along the outer side of the lower leg 10. Once the shuttering has been filled the
concrete may be levelled using conventional techniques and cure will start.
[0021] Because the vulnerable edge regions of the concrete are, in use at the present invention,
protected by the material of the shuttering set it is believed that it will not be
necessary to wait for a high level of cure before foundation walls can be constructed.
Typically, even with a standard concrete mix, work on building the foundation walls
can start within a few hours of pouring the concrete - certainly on the same working
day.
[0022] The foundation walls are constructed on the horizontal leg 11 and, if present, on
the horizontal leg 30. When the wall is constructed on the horizontal leg 11 the outer
edge of the horizontal leg (i.e. at the juncture with the vertical leg 10) is used
by the bricklayer as a guide for the position of the base course. Because the shuttering
set has been factory produced and precisely formed no onsite checking or layout is
necessary for the bricklayer - he can simply start laying his bricks on the horizontal
leg 30 using the outer edge thereof as a guideline. Similarly, if an inner leaf is
to be constructed it can be constructed either on the horizontal leg 11 if this is
wide enough or on the horizontal leg 30. Once a suitable number of courses of bricks
or blocks have been laid the remaining structure, which may for example be a pre-fabricated
structure such as a conservatory, or a site constructed structure of for example brick
or block, can be built atop the existing foundation walls.
1. A method for providing a foundation for a building comprising the steps of: pre-forming
a shuttering set (4) so that in transverse cross-section the shuttering set (4) defines
a vertical leg (10) for retaining concrete and a horizontal leg (11) that extends
inwardly of the building from the top of the vertical leg (10) so that it is, in use,
supported by the concrete retained by the vertical leg (10); positioning the shuttering
set (4) at a use location; levelling the shuttering set (4); pouring the concrete
into the shuttering set (4) to be at least partly retained by the vertical leg (10)
and to underlie and provide support for the horizontal leg (11); allowing the concrete
to at least partially cure; and constructing a wall on the horizontal leg (11) aligned
with a guide provided by the horizontal leg (11).
2. A method according to claim 1, wherein the guide is provided by an outer edges of
the horizontal leg (11) where it joins the vertical leg (10).
3. A method according to claim 1 or claim 2, wherein the shuttering set (4) is supported
in position on a plurality of height adjustable struts (5), the step of levelling
the shuttering set (4) comprising adjusting the height of the struts (5).
4. An apparatus for carrying out the method of the invention, the apparatus comprising
a pre-formed shuttering set (4) that, in transverse cross-section, defines a vertical
leg (10) for retaining concrete and a horizontal leg (11) that extends inwardly of
the building from the top of the vertical leg (10).
5. An apparatus according to claim 4, further including a plurality of height adjustable
struts (5) which, in use, engage between the ground and the shuttering set (4) in
order to support the shuttering set (4) in position.
6. A method according to claim 3 or an apparatus according to claim 5, wherein each strut
(5) has a sole plate (6) at its lower end which rest against the ground, which sole
plate (6), in use, is covered by the concrete during filing so as to restrain the
shuttering set (4) from floating as the concrete level rises.
7. A method according to any of claims 1 to 3 or 6 or an apparatus according to any of
claims 4 to 6, wherein diagonal bracing bars (14) are attached to the shuttering set
(4) in order to brace the structure.
8. A method according to any of claims 1 to 3, 6 or 7 or an apparatus according to any
of claims 4 to 7, wherein the shuttering set (4) includes a second vertical leg (12)
that extends upwardly from the inner edge of the horizontal leg (11) to retain concrete
so that the finished surface of the concrete is above the level of the horizontal
leg (11).
9. A method or an apparatus according to claim 8, wherein a second horizontal leg (30)
extends inwardly of the building from the top edge of the second vertical leg (12)
to provide a surface on which an inner leaf of a cavity wall may be constructed.
10. A method or apparatus according to claim 8, wherein the first horizontal leg (11)
is wide enough to accommodate, in use, both the inner and outer leaf of the required
wall, the inner leaf being constructed at a pre-determined spacing from the outer
leaf or utilising a second guide provided by the shuttering set (4).