Learn to Build – The Floors
Before deciding upon the type of floor, you must consider the question of hot water under floor heating. On the ground floor the pipes are laid upon a 100mm bed of polyicyanurate or 125mm of polystyrene and then screeded over with a sand cement mix.
The first floor with its timber joists should have the hot water central
heating pipes attached to the sides of the joists close to the top edge, zig zagging backwards and forwards the full length of the room.
Where joists are notched for pipework, the notches must be at the top of the joist, no deeper than 0.15 of the joist depth and positioned in a zone between 0.1 and 0.2 of the span.
Holes in the joist must be in the centre of the joist depth, and must not be more than 0.25 of the depth and must be in a zone between 0.25 and 0.4 of the span. There must be at least 100mm horizontally between any notches or holes.
Softwood or hardwood tongued-and-grooved flooring should be cramped up and either double or secret nailed to each joist.
Nails should be two and a half times the thickness of the boarding and punched home.
Chipboard should have the tongued and grooved edges glued together and be laid with the long sides at right angles to the run of the joists. They should also be glued to the joists.
The boards should be nailed with ringshank nails two and a half times the thickness of the board or screwed at 200-300mm centres along the joists or beam-and-block floors.
Boards must run to a joist on all sides or be supported by a beam-and-block floor with an expansion gap of at least 10mm left where the boards adjoin or butt up to a rigid upstand or wall.
The void between the joists should be filled with glass fibre insulation before the wiring is run, and the plasterboards are fixed in place.