Damp walls

[Julian3449]

We have a stone built 4-bed house in Herault (34) and little money.

Some of the external walls are showing damp in some areas. The region does not get a lot of rain , so I am not unduly concerned.

The house appears to be built directly onto the ground, with shallow foundations if any.

Since they are made of thick stone, I guess a damp proof course is impossible?

Does anyone know of a cost-effective, non-invasive method of treating the walls to stop rising damp?

Julian-34 (region and age)

[Ron Avery]

If the exterrnal walls are showing damp this could be due to ingress from above, have you guttering all the way along above this wall?  If you have, you may need to re point your stones as the old lime/sand pointing does get a bit soft after a while and acts like a sponge,  which in fact is what it is intended to do.

As far as I have been told, traditional stone walls do not have a damp course and they should absorb the damp from the ground up to about a metre and that is why they have sand and lime pointing. You can water proof interior walls if water ingress is a problem with a special sealing paint ( designed for " les caves)   from Bricos, but it is not cheap, a tin is about £30 and that only does about 25 sq metres 

[Hegs]

Check out www.periodproperty.co.uk "Agony Uncle" section. Usually the advice goes along the lines of:

- Obviously check for rainwater infiltration first as Ron has suggested

- Otherwise the problem is usually due to later changes to the property stopping the walls from breathing

- Remove any earth buildup around house, any concrete paths around the house, dig drainage channels to allow moisture to drain away from house etc

- Remove anything stopping the walls from breathing at a low height (concrete render etc)

- Ensure house is properly ventilated

Apparently things like chemical DPC and sealants shouldn't be used without great thought as they stop the walls from breathing and can make the problem worse in the long run.