If you have chipboard floors which are smooth and level, you can lay tiles directly on top. Remove any protruding tacks or nails or drive their heads below the surface using a hammer and nail punch (1); drive any screws just below the surface. Any loose boards should be refixed - use screws in upstairs rooms as hammering could damage the ceiling below.
Make sure that there are no wires or plumbing pipes where you are driving in nails or screws.
Floorboards will need to be covered with sheets of 3mm thick hardboard. If you lay tiles directly on to floorboards, it is likely that the boards will start to show through and cause premature wear, especially in areas of heavy traffic.
Use sheets 1220mm (4ft) square, or 1220mm x 610mm (4ft x 2ft).
Condition the boards to the room's atmosphere before laying them. This prevents them warping later. Brush water on to the mesh-side of the board, then stack the boards for 48 hours, mesh-side to mesh-side, in the room in which they are to be used.
Lay the boards smooth-side up. Use 19mm annular nails, hardboard nails or staples. Fix them every 150mm around the edges and across the boards. Butt up the edges of adjoining boards tightly, and stagger them in brickwork fashion so that joints don't coincide (2).
When cutting boards at skirtings, you do not need to get a perfect fit - a gap of around 6mm will be covered by the tile.
Any dampness in a solid floor must be treated before laying a floorcovering. There are various damp-proofing compounds that can be brushed on to cure the problem.
Holes or uneven patches can be filled with a self-levelling compound which is poured on the floor and spread out with a trowel (3 & 4). It will then set to a level finish.
A concrete floor which gives off dust when brushed can be treated with a purpose-made sealer or with diluted PVA adhesive.
A new concrete floor must be allowed to dry out before laying tiles. Allow about one month for every inch of thickness.
If wood preservative has been applied to floorboards, don't lay tiles, even if the boards are covered with hardboard. There is a risk that the preservative could bleed through and ruin the tiles.
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