We have established that our buildings must be raised off the ground, so that we can slide steels under the building to lift it in order to comply with the Caravan Acts – it also helps it to breath, as there is an airflow under the floor cassette. The other benefits of a raised building is that no termites can access the unit, flood and splash-back doesn’t affect the building and you are not relying on a damp proof course (DPC) to isolate the building from ground water and rising earth salts. Here is how we can achieve a satisfactory foundation:
Pour a concrete slab and then place concrete blocks around the slab to the exact footprint of the building and also where any internal load-bearing walls are indicated on the drawings. Leaving gaps to prove that steels can be inserted and the building complies with the above rules. The floor cassette ring beams usually composed of 2 x 222mm x 44mm beams bolted together are then supported by the blocks. The joists also 222 x 44 mm or 197 x 38mm are installed and 22mm t & G (4 sides) floor deck is installed. In order to comply with the two part caravan act a double centre beam is installed so the floor cassette is effectively in two parts (see fig 1). The central row of floor-boards are left out until the rest of the building is completed so we can photograph the centre floor beams being bolted together (last act of construction rule – see above).
Urban Plinths are an economical and ecological method of providing a foundation for a single floor buildings. Plinths simply sit on the ground and the floor ring beam sits on them.
The installation procedure is very simple and can be seen illustrated in our brochure TEE 6. We are often asked are they legal? The answer is yes they are as they have been engineered into the buildings integrity. In the old days building inspectors used to make a builder dig down a minimum of 2’3” (approx 700mm) and then pour concrete into a hole (footing) to build off. Why excavate solid compacted ground that has been there for millions of years to replace it with something you mixed that day?
Other: Unless the alternative methods either meet building regulations or have been designed by a chartered structural engineer, they will not be acceptable if planning permission has been obtained, as the local building control need proof that they are fit
for purpose. Other methods include digging ‘pockets’ 50cm x 50cm x 40cm deep and filled with compacted MOT type 1 stone or pea-gravel the plinths are then placed on them. Sunken cut lengths telegraph poles encased in concrete, steel driven piles and spread matting are all methods that can be used. How to decide on a foundation mainly depends on the loads that the proposed building will impose on it. This is a very complicated subject and space does not allow us to discuss it here. All design and calculations required to meet UK Building Regulations are part of the “complete structural timber frame package” supplied by Urban Marque Ltd
AT ALL TIMES THE CLIENT IS RESPONSIBLE FOR THE GROUND CONDITIONS Urban marquee Ltd or Timber Engineering Europe Ltd will not be responsible for any ground-works or soil/land conditions
A typical floor cassette would be factory cut and installed on site. An illustration of a cassette is shown on the next page.(fig 2) The floor cassette members are a double ring-beam and central beam made up of two timbers either 44mm x 222mm or 38mm x 197mm bolted together. The joists between the beams will be the same size as the
beams but single timbers. Insulation must be installed between the joists and we use 200mm Rockwool or similar stone or glass wool. A batten is fixed to the sides of the joists and a rip of plywood is dropped into the void to make a “floor” to hold the insulation in the void. The flooring grade chipboard (22mm T & G x 4 sides) is then installed to make a floor platform. We use Egger Protect P5 flooring chipboard. This can be exposed to the elements for 42 days before it becomes U/S and when the job is complete, a protective cover peels off to reveal a clean undamaged. floor. Size: 600mm x 2400mm x 22mm