Rising Damp TreatmentSpecialists in Harrow

The standard remedial approach is a chemical damp proof course: a water-repellent silane/siloxane formulation introduced into the mortar bed so it lines the capillaries in the masonry and stops water climbing. Cream formulations are injected into drilled holes at set centres along a single mortar course and are the usual choice on solid brick, because the cream stays where it is put rather than running into voids.

We install Sovereign and Wykamol systems as an approved contractor, which means holes at the spacing and depth the manufacturer specifies, in the correct course, and product used at the stated coverage rate. Where a wall is rubble-filled, very wet, or built in stone with wide irregular joints, the specification changes, sometimes to a higher-volume injection, sometimes to a different approach entirely.

Once a wall has been wet for years it holds chlorides and nitrates brought up from the ground. Those salts are hygroscopic: they attract moisture out of room air, so plaster containing them stays damp even after the masonry below has dried. That is why old plaster is removed, normally to around a metre above the last visible sign, and a salt-retardant render system is applied in its place.

The usual build-up is a sand and cement render with a waterproofing additive and salt inhibitor, then a skim finish. Alternatives include renovating plasters and dry-lining on a membrane where a wall must not be wet-plastered or where the room needs to come back into use faster. Freshly treated walls need drying time before they are fully decorated, and we tell you how long before you order paint.

A perfectly good damp proof course can be defeated by something bridging it. Raised patios, new paths, flower beds and gravel piled above DPC level all give water a route around the barrier. So do render coats carried down over the DPC, rubble left in a cavity, and internal solid floors poured above the wall's damp proof course level.

The survey looks for these because correcting them is often cheaper and more effective than any injection. Lowering ground levels, cutting back render, forming a clear margin or installing a drainage channel can resolve damp that had been diagnosed elsewhere as a failed DPC.

Victorian and Edwardian solid-brick terraces are the most common case: nine-inch walls, a slate or bitumen DPC that has broken down, and the damage concentrated on party and front elevations. Interwar cavity-walled houses more often suffer bridging or debris in the cavity than a wholesale DPC failure. Stone cottages and rubble-filled walls need a different injection strategy because the wall is not a uniform absorbent block.

Flats and maisonettes at ground level are treated the same way, though access, shared walls and lease conditions shape the sequence. Commercial ground floors: shops, offices, workshops; add trading hours and stock protection to the plan, but the technical work is unchanged.

There are no published prices for this work because no two walls are the same. Length of wall, wall thickness, height of replastering, plaster type, access, joinery removal and any bridging corrections all change the scope. The free survey exists so the quotation matches the property rather than an average.

Every job is quoted as a fixed price, never a day rate. Payment is 50% deposit and 50% on completion, by bank transfer. You know the total before anything is drilled.