Concrete Floors or Timber?
The two major forms of floor construction are 'suspended' and 'solid'. Suspended floors are usually made out of quality or economical timber boards or waterproof chipboard sheets fixed on top of joists. They can also be constructed with concrete plank or post and beam. Solid floors have a more substantial stone and sand sub-base, cast in concrete and with appropriate insulation and a damp-proof membrane. There are variations on these two themes, but the choice really depends on the kind of eventual floor finish you want in your home.
When the intention is to lay carpet, suspended timber floors offer greater comfort, because they 'give' slightly and produce a softer walking surface. High quality timber tongue and groove flooring can be left uncarpeted, if the desire is to create a stylish and contemporary home. Alternatively, flooring quality chipboard tongue and groove sheets are the cheapest material, and the preferred choice of commercial developers keen to maximise profit. The main problem associated with economical materials used for suspended timber floors is that they quickly deteriorate. Central heating causes them to expand and contract and, before very long, the gentle 'bounce' effect can become a frustratingly audible creak and squeak. Pinning, screwing and even gluing floorboards down has become a regular chore amongst new homeowners up and down the country. Though excessive noise is often the result of inferior materials compounded by poor installation, a suspended chipboard floor should only be considered when cost and design practicalities have priority over more stable and durable alternatives.
Suspended floors require firm regular support from sleeper walls positioned below the damp-proof level. These will be set out on the approved construction drawing and should be built at the same time and together with other sections of the sub-structure.
A solid concrete slab is the perfect base for laying ceramic floor tiles, slate, stone, marble or terracotta in kitchens, dining rooms and hallways. Other rooms requiring a softer feel can then be carpeted with a quality underlay to improve the level of comfort. It is worth noting that a compromise between the two constructional forms of flooring exists in the form of a suspended concrete floor. This helps maintain a completely dry sub-base through continuous air circulation and venting in the void. It can also be set low to allow insulation and underfloor heating to be included within a top screed, which could then be completed with distinctive ceramic floor tiles. This arrangement is typically Mediterranean in structure and form, being cool in summer, warm in winter and elegant in style.
Concrete floors, unless suspended, are laid on a sub-base incorporating a dampproof membrane and insulation. The building inspector will need to assess this type of floor before the slab is cast so, once the damp-proof course and membranes are ready, book an appointment so they can attend the site to examine the installation work. Unlike the foundations, concreting of the floors is limited to small, individual areas and therefore the volumes are much easier to handle. However, levelling of the surface needs to be done with greater care, because it will be a base for decorative materials. A long, straight piece of timber worked from side to side helps to create the level and a wooden float is then employed to smooth out any irregularities. A mechanical power float finish should also be considered.
Refer to the approved plans for the size of timber floor joists required. These must be 'tanalised', a process in which timbers are impregnated under pressure to drive tanalith-oxide preservative deep into the cellular structure. This is designed to protect the joists against wet and dry rot, woodworm and other insects for at least 20 years. Set out the joists on top of the damp-proof course, space according to the architect's drawing and ensure cambers (if any) face upwards. Nail a lath across the joists to temporarily hold them in position. Using a long straight-edge and a spirit level, check the timbers in both directions and pack the joist ends as necessary, until they are completely level. Finally, wall the joists into the inner leaf to permanently secure them.
