How do I deal with a damp building?

Tŷ-Mawr ‌‌ posted this on 19 Oct 2023

We are frequently asked for advice on how to deal with a damp building - so if you are renovating one, remember you are not alone!

The guiding principle should be to deal with the root cause of the problem(s), instead of simply covering over the symptoms.

We commonly see evidence of poorly-functioning rainwater goods and detailing which let water into the building: this water can become trapped behind any cementitious render or plaster, preventing the walls from drying out. It is pointless to carry out any internal plastering and decoration without first dealing with the existing moisture in the walls. The moisture would continue to degrade the new plaster work, resulting in further cost and disruption.

So your first task is to repair gutters, downpipes and land drains – this will stop any further accumulation of moisture in the walls.

Then remove any inappropriate cementitious render and/or internal plaster. This can be carried out straight away.

You must now leave the building for as long as is necessary to allow the walls to dry. The process of drying is dependent on weather, building/wall orientation, and time of year - so can take considerable time. If new plaster/render is laid onto damp walls it will extend the drying time and be more susceptible to frost damage. Paint finishes will discolour whilst the plaster/wall dries.

When the walls are fully dry, the process of rendering/plastering can begin.

Once the new plaster is fully dry, apply an appropriate breathable paint.

Damp buildings are difficult but not impossible to deal with. Unfortunately, we have seen too often that this type of work has been rushed, which just causes further problems.

Categories: Damp Buildings