Why basements get wet
Below ground, walls and floors are in contact with soil and groundwater. Without a barrier, moisture passes through masonry and floors, causing damp, salt deposits, mould and flaking finishes. Many older Tyneside homes have cellars that were originally built for coal and storage, not as living space, and they often have no damp proof barrier at all.
The main approaches
- Cementitious tanking, a waterproof coating applied to the walls and floor to resist water pressure
- Membrane systems, where a dimpled membrane lets water drain away to a sump and pump, rather than stopping it
- A combination of the two, with drainage as a back-up for higher-risk situations
The right option depends on how wet the space is, whether there is groundwater pressure, the condition of the walls and what the room is to be used for. A store needs a different standard from a bedroom or study. We look at the actual conditions and avoid a one-size-fits-all approach.
Preparation is everything
Tanking only works if the surface beneath is sound. Failed plaster is removed, loose mortar repointed, cracks and voids filled, and any salts dealt with. Where walls are old and uneven, extra preparation is required. Applying a coating over damp or salt-contaminated plaster is a common reason for failures.
Drainage, ventilation and services
Waterproofing works best alongside good drainage. Faulty gutters, leaking downpipes or defective drains outside can load the wall with water, so we check these first, see underground drainage repairs. Habitable basements also need adequate ventilation and, in some cases, means of escape. If the floor is to be lowered to increase headroom, see cellar floor lowering.
Local considerations
Terraced houses in Newcastle often have cellars under the front rooms, and the ground close to the Tyne and its tributaries can be damp. Properties near the coast may also have salt in the masonry, which affects the choice of materials.
Converting a basement into a habitable room is likely to need Building Regulations approval. See GOV.UK for guidance, and the Planning Portal for planning questions.
Frequently asked questions
Can any damp cellar be tanked?
Most can, but the right system depends on the walls, water levels and use of the room. We inspect first. If water is entering because of an external fault such as a leaking drain, that should be dealt with as well.
Do I need a sump pump?
Not always. Pumps are used where water has to be drained away, for example with membrane systems or where groundwater is a concern. Dry, lightly damp cellars may only need tanking.
