Screening a solid floor

Filed Under: Do it yourself, Home repair, Remodeling    by: ITC

Screening your floor gives vital protection to a new layer of damp proofing and is an essential preparation before replacing floor covering.

It can be done in two ways. If the unevenness is slight, or you want to cover the existing flooring without lifting it, the best method to use is a self-leveling flooring compound. Make sure your floor is clean, dry and dust-free. If it is at all dusty, you should treat it with a proprietary concrete sealer before applying the flooring compound.

Mix the compound with water until it has a creamy consistency, and then pours enough on the floor to cover an area just under 1 sq m (1sq yd). Using a steel float smooth it out so that nowhere is the layer thicker than 3mm (Vain).

Then move onto the next square. Remembering that the compound will level itself out, so removing float marks and producing an acceptable finish. Leave it for a week or longer before laying the flooring. A second application, to smooth out slight lumps and bumps, can be applied after two or three days, but no more than three coats should be used otherwise there will be a risk of cracking at a later date.

The second method of leveling, using a mortar screed, is slightly more arduous but it does give the damp-proof membrane greater protection. Working from the far end of the room towards the door, divide the flood into strips about 1m (3ft) wide using 50 25rnrn (2 x line) softwood battens, and use more battens around the walls. Make sure that they are level with a spirit level, and if they aren’t, pack them out with scrap wood.

It is vital that you get all the battens level because they serve to guide you when you start laying the screed. If you don’t have them level, then your screed won’t be true and that’ll cause more problems when you come to lay the final surface. Cover the floor. a section at a time, with a 1:3 cement to sharp sand mortar, mixed with the minimum of water to the consistency of brown sugar_ Using a stiff board, scrape jt level with the battens and tamp it slightly as you go, using a steel float to give it a smooth finish.

To get the best finish to your screed keep the blade damp to stop the surface from dragging, but don’t make it too wet. When you complete each section remove the guide batten furthest from you and fill in the resulting channel before tackling the next section.

If you lay a screed during a warm dry spell it’s advisable to lay a plastic sheet over it for at least three days. This stops the mortar drying out too quickly and lets it cure properly. Even in milder weather it’s still best to sprinkle water gently over it twice a day for a few days. If the mortar dries out too quickly it will be below strength and will probably crack as it dries. Finally make good the walls and replace the skirting.

The big drawback with this method is that it raises the level of the floor by 25mm (1 in). Strictly speaking you should dig out the existing floor to the required level before starting, but this carries the risk of damaging any existing damp-proof membrane. One way of accommodating the extra thickness is to trim the bottom of the doors and build up any existing external doorsteps.

Do make sure that you don’t reduce the floor/ceiling height below the Building Regulations minimum of 2.3m (7ft 6in) and remember to do something about the change in level at the door thresholds: a shallow ramp is better than a shallow step.

There is another option, and that is not to lay a membrane at all. Instead you select flooring that can be laid using cement-based flooring adhesive. The former lets the damp through. so you should choose material that won’t be harmed by it, and the latter acts as a sort of damp-proof membrane itself.

But. as it is a makeshift solution. it will not always work and there is nothing to stop the damp rising through the walls. The floor will therefore be attacked from the edges. which can be just as harmful and the result will be that the whole floor will eventually have to be replaced, not only giving you extra work but also further expense.

Be Sociable, Share!

Tags: , , , , , , , , , , , , , , , , , , ,

Leave a Reply


5 × three =