There are a number of damp patches on the interior walls in two separate rooms in our house

April 2014

Question

I recently inherited an old detached house that belonged to my aunt. It’s located in a rural area. My partner and I have been renting accommodation for the past few years and have some savings, which we would like to spend on renovating the property before we move in.

The house has been uninhabited for a number of months but we have noticed that there are discoloured patches (light brown) on the interior walls in two separate rooms.

We don’t know if the patches are a recent occurrence or have been there longer. We don’t have any knowledge in this area and don’t know what’s causing it or how to fix it. Any advice would be much appreciated.

Answer

This house has been occupied in recent times and presumably it has been upgraded in the last 30/40 years. It would be useful to know the original construction and subsequent repair and upgrade work.

Typically when houses were refurbished, external walls were re-rendered, internal walls dry lined, ground levels raised and roof finishes replaced.

Both traditional and modern methods of building are able to function efficiently if they are done well and are properly detailed. But over the last four decades, as the understanding of traditional solid walls has largely disappeared, modern techniques have been applied to breathing structures, to disastrous effect.

Cement renders, along with “plastic” paints, waterproof sealants and damp proof courses, act as barriers to the wall’s natural ability to breathe. This is when trouble occurs, with a mix of technologies that trap water within permeable materials exacerbating the very problems they are trying to resolve.

The source of dampness can be remote from the place where you are seeing it. Venting vacant buildings is crucial. Lack of ventilation can cause rot to manifest.

Virtually every old house will have some sort of damp problem, varying from something simple that is easily remedied to a long-standing issue that is impossible to resolve and may have to be ‘managed’ and accepted.

Damp staining can be associated with condensation, penetrating damp, rising damp, plumbing leaks and the effects of salts from rising ground salts; chimney flue gases on interior walls; urine saturation where animals have been kept.

The discoloration is likely to result from one of the aforementioned issues. Your problem may be simple to resolve. The most important rule is to diagnose the true cause and, if possible, tackle the problem at source rather than simply treating the symptoms.

Old buildings require different degrees of interest and skills, and not all jobs are advisable for the untrained, or even for the seemingly dextrous. In order to assess the problem, I suggest you contact your local chartered building surveyor with experience of old buildings, who can also advise you on the renovation of the property.

Jim Drew is a member of the Society of Chartered Surveyors Ireland