With the autumn rains having definitely arrived, our building surveys will begin to find damp that had disappeared during the dry summer. Before going to expensive rebuilding works, firstly consider if there is any way of keeping the water away from the structure.
The installation of roof edge guttering and downpipes connected to drainage or garden water storage would considerably reduce the rainwater currently accumulating around the perimeter of the building. The positioning of garden sprinklers should also be reviewed for similar reasons.
If still damp, consider the installation of better drainage around the outside of the external walls, ideally down below the lowest internal floor level, with appropriate infilling above so that water seeping in from the soil will run down into the drains and be carried away instead of saturating the building and eventually penetrating to show on the inside.
Only if these measures fail or only in addition to these, should you consider the installation of waterproofing on the inside of the walls. That will inevitably hold the moisture in the structure, which can cause it to crumble and corrode, or force it to rise until it reaches a level where it can ‘flow’ over the top of the waterproofing.
Bear in mind that it will take at least another warm summer before the damp already in the building dries out. Damp under marble of ceramic floor tiling can take a number of years to dry out, with the adjacent walls acting as wicks to draw up the water underneath and thus show damp at lower levels. Much better not to have the damp underneath at all, so even in a dry house don’t let that bath overflow or leave the kitchen tap on in error!!
Campbell D. Ferguson, FRICS, is a chartered surveyor in Spain.His company Survey Spain Network arranges valuations and surveys by RICS chartered surveyors anywhere in mainland Spain and the Balearic and Canary Islands, and Gibraltar. This includes valuations, building surveys, structural surveys, building inspections and investment and development appraisals.