ASK THE EXPERT

Douglas Kent, technical and research director at the Society for the Protection of Ancient Buildings (SPAB), answers your renovation queries

Q The internal walls of our barn conversion keep leaking when we have had rain. What is the best course of action? Should we seal the external brickwork with a waterproofer?

The best advice I can give you is to investigate and deal with the cause of the rainwater ingress affecting your barn conversion. This may be straightforward, such as overflowing gutters (particularly with the heavy rain that we have experienced in recent years). Alternatively, it could be related to the nature of the wall itself, including repointing at some stage using an inappropriately hard cement mortar rather than a lime-based one. Cementitious mortars tend to be of low permeability and are brittle, allowing rainwater penetration via hairline cracks. Repointing may be required using a suitable lime mortar or, in a more extreme case, the application of a lime render or other protective finish may be a recommended course of action.

I would very much discourage you from attempting to seal your brickwork with a waterproofer. Conservation organisations such as the Society for the Protection of Ancient Buildings have serious concerns about the unintended, long-term risks associated with such products. Concerns include the potential to trap moisture and further increase dampness, even with waterproofers that are said to be ‘breathable’.

It is also worth employing a chartered surveyor or other specialist adviser to diagnose the cause of the dampness.

Q Is it advisable to install a wood-burning stove in our thatched cottage?

Historic England and the National Society of Master Thatchers strongly advise against installing wood-burning or multi-fuel stoves in thatched properties following recent research that shows they are one of the most common causes of fire. Where a wood-burning stove is put in despite this, it is prudent to install a modern chimney liner at the same time. Some liner manufacturers, however, require a rain cap be fitted to minimise the likelihood of corrosion of the lining but such caps can increase the risk of fire, so are not recommended with a thatched property.

If you have a renovation question for Douglas, email periodliving@futurenet.com*