B) In what context do you think the following words and phrases will appear in the text?

• concrete slabs •honeycomb sleeper • chequerboard pattern • bituminous • surface• reinforced • floor boards • raft foundation • wall plates

c) Read the text and check your answers:

FLOORS

The main functions of floor are:

1) to support the loads from the finishes, people, machines, furniture and fixtures;

2) to provide a level surface for normal uses in a building;

3) to provide a level surface for any floor finishes that are applied.

Floors are normally classified as: ground floors and upper floors.

Ground floors are either concrete slabs laid directly on the ground on hardcore beds or suspended timber structures supported on honeycomb sleeper walls that stand on concrete slabs.

Upper floors are either reinforced concrete slabs or suspended timber structures that are supported on load-bearing walls.

This unit describes these different types of floor and their construction in detail.

The oversite-concrete slab

At ground-floor level, the concrete slab that rests on the ground floor must:

1) provide a total barrier to dampness in the ground by the use of a damp-proof membrane;

2) prevent termites from entering the building;

3) prevent the growth of vegetation.

Concrete oversite slabs are used for both suspended timber floors and concrete floors.

The difficulty with suspended timber floors on concrete oversite slabs is that extra care should be taken to achieve the three conditions. The space under timber floors at ground level must be well-ventilated and the timber treated with preservative to ensure that it stays dry and resistant to insects such as termites. Because access is awkward it is difficult to observe and control potential problems.

A typical oversite concrete floor slab that is laid directly on the ground is made from concrete (proportion: cement- sand- water –1:3:6). Since concrete shrinks as it dries it should be laid in areas that are no larger than 3 metres by 3 metres or 10 square metres. If the concrete is placed in more than one section at a time, then be sure not to put it in adjacent bays at the same time. The concrete should be poured in a chequerboard pattern so that the spaces left after the shrinkage can be filled in as each section dries.

Concrete ground-floor slabs

Three different types of concrete ground floor prevail:

1) an oversite concrete floor below a suspended timber floor (Figure 11.2);

2) the ground-floor slab in a brick or masonry building;

3) a raft foundation in a timber frame building (Figure 11.3).

The construction process is similar for each type and here the following aspects should be provided:

· a hardcore bed;

· a blinding;

· a damp-proof membrane (dpm).

Raft foundations also need steel reinforcement.

Figure 11.2 Oversite Concrete Floor below a Suspended Ttimber Floor	Figure 11.3 Raft Foundation

Building a suspended timber floor

The following elements are necessary for building a timber floor: honeycomb sleeper walls; air bricks; a damp-proof course; walls plates; floor joists; floor boarding.

Honeycomb sleeper walls are brick or block walls built over the oversite concrete so that air can circulate freely in the gap to all parts of the underfloor.

Airbricks are special bricks with holes in them that allow air to flow through.

Damp-proof course (dpc) is usually bituminous felt laid on the sleeper walls in widths of 102.5 mm to prevent dampness entering the wall plate.

Wall plates are timber pieces about 75×100 mm that are used as bases for fixing floor joists. They are laid carefully on the dpc along the length of the sleeper walls.

Floor joists are the pieces of timber that span between the wall plates and support the floor boards.

The type of floor boarding depends on availability and preference. Standard choices are: softwood boards; plywood; blockboard; chipboard.

Softwood boards should be at least 25 mm thick and less than 100 mm wide. This reduces the shrinkage gaps between boards and the possibility of distortion.

5 Read the text again and answer the questions that follow (1-8):

1. What are three main functions of floor?

2. What is the normal classification of floors? Characterize it.

3. How does a concrete slab function?

4. Why is it necessary to ventilate a space under timber floors at ground level?

5. What are the requirements for a typical oversite concrete floor slab?

6. What types of concrete ground floor prevail?

7. What are the necessary elements for building a timber floor?

8. What is the appropriate size of softwood boards to reduce shrinkage gaps?

Follow-up

6 a) Find the synonyms in the text for the following words:

Kind, construction, obstacle, to guarantee, abutting, contraction, component, building process, straining, to penetrate.