The hardcore bed

The purpose of the hardcore bed is to:

1) provide a 1) _____ bed that will keep the concrete slab warm and dry;

2) resist the growth of vegetation;

3) provide a level base for the oversite concrete.

The hardcore bed consists of material that resists 2) _____, such as broken brick, stone or rock.

The pieces should be large enough to ensure plenty of space so that 3) _____ isn’t trapped within the hardcore, the layers should be put down about 150-200 mm thick and flattened by hand with a tool called a 4) _____ to consolidate them. Also the machine called a plate vibrator can be used for large areas of hardcore.

The blinding

The finished hardcore has a rough, 5) _____ surface that should be smooth before laying the damp-proof membrane. It is done by laying about 50 mm of sand, ashes or weak, dry concrete slurry called blinding over the surface of the hardcore. The surface should be carefully leveled and there are no sharp 6) _____.

The damp-proof membrane

The membrane’s purpose is to prevent 7) _____ entering the building through the concrete slab. It is usually a heavy-duty polythene sheet that is tough enough to be handled on a building site without 8) _____ or puncturing. The material should stay intact even when workers walk over it while they fix 9) _____ in the floors and lay concrete. The dpm should be laid so that the edges 10) _____ the joints.

10 Put the steps of making a simple raft foundation slab into the correct order: