There are several possible ways of damp proofing / tanking your cellar and it is difficult to suggest the best way without actually seeing the cellar. Below are some suggestions that would be suitable in most cases.

1. FLOOR

(a) Paint the floor with 3 or 4 coats of a water based rubberised bitumen emulsion (EABASSOC RBE). Then put sand/cement screed on top (approx. thickness 50 mm). If the original floor is brick or flagstones, it would first be necessary to repair any decayed mortar joints.

(b) Alternatively put down a layer of sand then cover this with a layer of polyethylene damp proof membrane which is a plastic sheet obtainable from builders merchants. The sheet must be lapped up the walls and can be secured using flashing tape. Any joints in the plastic sheet should be made by holding approx. 10 cm of each piece of plastic together then folding them so that one of the pieces goes back on itself and the other lies on top. Then cover the plastic sheet with sand/cement screed.

2. WALLS

(a) On concrete, or brick walls where the pointing is good, you could use RBE as follows. Apply a coat of diluted RBE as a primer. Then apply 3 or 4 coats of undiluted RBE. If using the plastic sheet for the floor as in 1 (b), use flashing tape to secure the plastic sheet which has been lapped up the wall. Apply a sand/cement render on top of the RBE, approx. thickness 50 mm. The use of a waterproof cement is unnecessary.

If the pointing is not good you will need to apply an additional sand/cement render approx. thickness 20 mm directly onto the wall before applying RBE and render as above.

We do not recommend using a penetrative sealant because there is no guarantee that it will actually penetrate, especially if the bricks are damp. If you are using RBE, definitely do NOT use a silicone based penetrative sealant. Silicone is a water repellent and RBE is water based. Therefore RBE would not adhere to the walls if a silicone penetrative sealant has been used.

If the wall is damp or if the hydrostatic pressure is large, e.g. when the water table rises during winter, there is a possibility that the RBE and render may be pushed off the wall. If this is the case the render will need extra support. After the RBE has been applied, coarse wire mesh can be nailed to the wall as a support for the render. When putting up the wire mesh first put strips or small squares of flashing tape on top of the cured RBE at the points where the nails will be used. Apply 2 or 3 coats of RBE on the nail heads and around the nails after the wire mesh has been nailed to the wall. When applying the render, make sure that the render goes right up to the RBE coating on the wall and that there are no gaps between the wall and the render.

If the walls are too wet then RBE will not dry out and solvent based products will not adhere. An alternative solution is to use a thick studded plastic sheet. The thick studded plastic sheet is nailed to the wall such that the studs provide an air gap between the wall and the thick studded plastic sheet. An air gap must be left at the top and bottom of the walls to allow for ventilation. Sand/cement render should then be applied onto the plastic sheet. Thick studded plastic sheets are made by:

John Newton & Co Ltd (London)

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