Old buildings must be allowed to breathe while modern buildings rely on keeping water out with a system of barriers. Because most old buildings were constructed with solid walls without damp proof courses and originally had no roofing felt, rain or ground moisture could both be easily absorbed into property walls.

You don’t have to wait for a damp problem to solve it if a structure is under construction. The best course of action to the damp problem is always prevention. Nevertheless, an existing damp can still be rectified when handled by professional.









Penetrating damp on old wall and porous wall affected by damp

Preventive measures against damp walls

Constructing external ground levels at least 150mm below the damp proof course. If the ground water table level is above the DPC, water will definitely be absorbed by the bricks leading to damp

Installation of a Damp-Proof Course (DPC) and Damp-Proof Membrane. This prevents any further deterioration to the building and will stop any further expenses for preventing rising dampness in the near future

Providing a proper drainage system around a building

Application of waterproof renders and bituminous coatings on external walls. This is however a preventive method. If done to a damp wall without dealing with the source of damp, it could only make dampness severe with time

Proper ventilation of the property in plan to continuously evaporate moisture from permeable internal surfaces while the wind dries out any expected damp permeable external wall surfaces

Solutions to existing damp

There are various methods to treat damp in walls depending on the extent of damage or cause of damp. It is important that all solutions focus beyond the surface finish of the sections affected by the damp. But how about the moisture already existing in the damp wall?

Keep in mind that the most ideal time to treat penetrating damp is during summer because due to the heat and drought, that the walls are reasonably dried out when in repair.

1. Proofing between wall and plaster boards

Damp walls with plaster board finishes are most likely to be visualized with patches or stains on the surfaces of the plaster boards. Traditional builders would stick the plaster boards on walls using glue for a perfect bonding of the two and to also avoid direct contact of the boards onto the walls. However, in cases of dampness of the walls, the glue easily absorbed the moisture further thereby affecting the plaster boards. This is because the plaster boards also continuously absorb water from the damp glue. Renovation of such walls require that a proofing membrane be drilled into the wall before fitting the plaster board to the wall. A damp-proof course can be drilled into the wall using well treated battens or any metal strips. This acts as a proofing material between the damp wall and the plaster board. The plaster boards can then be drilled to the wall through battens after which finishing can be done.

2. Provision of a new cladding

Cladding is the application of one material over another to provide a skin or layer i.e made of timber, masonry, fibre cement or metal. This is applicable when the outer wall (and eventually the inner wall) have deteriorated considerably.

One can opt for a new (and waterproof) wall cladding when there is regular damp or damp penetrating into the house. The advantage of this is that the house will look like new again and one can to immediately insulate the outside walls.

3. Rendering the walls of the house/application of damp-proof paint

This requires that a protective layer should be applied to the outer wall to avoid or counteract penetrating damp. Rendering must be done after the wall is thoroughly cleaned to ensure that the rendering agent adheres better to the surface and that also existing cracks or fissures must be first repaired.

Note that this solves the dampness problem only after the source of dampness has been identified and critically dealt with. Outside this, the wall is likely to be vulnerable to dampness overtime. If your walls are still damp, the applied render is likely to trap water into the walls, creating a bigger problem later on.

4. Masonry protection/treatment

A masonry protection treatment when applied is to prevent further moisture from seeping into the property walls. This treatment method is widely used in recent structures not old buildings and has insulating properties which improve the thermal performance of your walls.

When injected, it penetrates deeply into the masonry before curing to form a breathable, colorless, water-repellent barrier. Water repellents are designed to line the pores of the masonry to form a water-repellent silicone matrix rather than a film on the surface. Because they line the pores rather than blocking them, the masonry is allowed to breathe so that any moisture in the masonry is allowed to evaporate naturally.

Water repellants are also effective at treating penetrating damp quickly and effectively. When applied/injected, these products are absorbed into the masonry, thus creating a barrier at the bottom layer and block any water from traveling any further into them.

5. Maintenance strategies in affected walls

Repairing masonry defects e.g. cracks in walls, faults doors. If there are any problems then this will need to be fixed with a suitable render

Preventing mould growth by improving the ventilation throughout the property

Improving the heating of the property and insulation of the cold walls

Replacing hard cement render or painting using a more suitable lime-based mortar.

Don’t get sucked into contracting services that only solve symptoms of damp which in the long run, makes it more expensive. Contact London Building Contractors for all your technical and professional expertise advice and solutions to all your damp issues.


Posted on: December 8th, 2021 by London Building Contractors No Comments

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