waterproofing basement walls

Penetrating damp is caused by water entering through defects in the structure of the house. The way to prevent and cure it is through a high standard of house maintenance. Keep the roof sound, and maintain the walls as described in this chapter. Repoint when it becomes necessary, and reined any defects in rendered walls. Seal any gaps between window and door frames and the walls with a proprietary sealant; keep gutters and downpipes clear of blockages; deal immediately with any plumbing mishaps that soak a wall; and apply an exterior grade si1icone based water repellent to porous walls. Damp in basements is common because they are below ground level and are surrounded by soil, in which damp is present. There is no practical way to eliminate damp from basement walls, but you can keep the damp at bay.

Prepare the walls by mixing a polythene sheet to them or by applying a damp-repellent liquid. Then fix bitumen lath to the walls with galvanized clout nails. Bitumen lath is a pitch-impregnated corrugated libre. The corrugations create channels on both sides of the material: thaw on the wall side form ventilation corridors in which the mist Can evaporate. Those on the room Side provide a receive plaster. Plasterboard can be used by do-it-yourselfers instead of plaster.  Another possibility is to build a partition wall clad with plasterboard close to but not touching the main wall of the basement, creating in effect a cavity wall, Normally the framework for a plasterboard partition is screwed to the wall, but for damp-proofing it should be fixed to the ceiling and floor, in the way outlined on page 126 for constructing a non-load bearing partition. It is a good idea to fit insulation blanket (of the kind used to line a loft) behind the plasterboard, so that the basement will be warm as well as dry. The floor of the basement will also need a damp proof membrane (such as clear polythene) to stop damp from rising through the floor. Overlap the membrane and the damp proof treatment on the walls.

wall repair patch

a hole in the wallIf a wall repair patch of rendering becomes loose and falls away, or a blister of loose rendering develops, repair it immediately, because the rendering is usually part of the weatherproofing of your home. With a bolster chisel and hammer, hack away the loose, crumbling material back to the brickwork. Begin in the centre of the blister and work outwards towards the edges, until you come to sound material. Similarly, with a bare patch, hack away all round the edge of the hole until you reach sound rendering. Make your own mortar for the repair 1 part of cement to 5 or 6 of sharp sand with a proprietary plasticizer added is a suitable mix or buy a bag of ready-mix and add water. In either case the mortar should be of a stiff consistency. First, treat the bare bricks with a pva building adhesive, mixed and used according to the manufacturer’s instructions. Apply the mortar in two stages. Place some on a hawk, hold it close to the wall and push the mortar into the damaged area with a steel float. Just before this first application hardens, scratch its surface in a criss-cross pattern with a knife or the point of a trowel – builders call it the‘scratch coat’. Leave for 24 hours, then apply the finishing coat, making it as similar as possible to the finish of the rest of the wall. For instance, if the wall is smooth, spread out the top coat until it  is slightly higher than the surrounding area. Then draw a batten across the surface of the patch in a sawing motion to remove surplus mortar. Leave it for about an hour to dry, then dampen it with water – you can apply this with an old paint brush – and smooth it off with the steel float.

The other finishes you can achieve, which are listed below, should be worked while the finishing coat is still soft, a few hours after it has been applied. Roughcast has a proportion of coarse aggregate in the final coat, which is thrown (literally) on to the wall as a wet mix, and left untrowelled. Scraped finish is achieved by leaving the final coat to harden for several hours, then scraping it with a tool, such as an old saw blade. Textured finish has the final coat worked with a trowel or even an old banister brush. Stippled effect, too, is created with a soft banister or dustpan brush. Wavy effect is produced with a piece of ribbed rubber when wall repair patch. Bold texture is achieved by dabbing with a fabric pad.

Damp wall | rising damp

damp wall | rising dampDamp wall is one of the worst defects that can affect a house. Even in its milder toms it is unpleasant but a serious outbreak will first destroy the decorations, then in time attack the woodwork, and eventually strike at the fabric of the building; it will make the place dank and unhealthy. There are three types of damp, each with its own causes and cures. Rising damp, as its name suggests, is damp rising up into the structure from the ground. Penetrating damp, caused by rainwater (or occasionally by water from a plumbing mishap), enters through defects in the shell of the building. The third type of damp is condensation, which originates inside the house. It is not always easy to decide which type of damp your Home is suffering from. In extreme cases it wil1take an expert to give a correct diagnosis. However, there are some general pointers. For instance, if the damp occurs low down on the wall near floor level, you can suspect rising damp. In, say, a bathroom that is prone to severe condensation, the paint can be lifted away from the wall by damp near the skirting, which is a symptom of rising damp, but the cause could equally be condensation streaming down to the bottom of the wall. The effects of condensation can also appear misleadingly on many parts of the walls and ceiling, but this type of damp wall is usually easy to recognize. It occurs when most of the windows are closed (which reduces ventilation) and after water vapour has been released into the air by cooking, washing clothes, or bathing.