Efflorescence

[Andyphilpott]

My house is 300 years old with granite block walls in the main. It was renovated in 2000 and the walls were rendered inside and then painted. The outside is also rendered using the coloured cement which is popular in Provencal villages.

In one spot I have a continual problem with effloresence - as well as the surface becoming powdery the underlaying render tends to come away from the granite. I have knocked it all back to the granite several times now but after around 12 months it recurs. I have tried unibonding it (onto the granite) as well as different types of render, but to no avail.

I am sure that it is not rising damp - the patch starts around 2 feet above ground level and goes on for a further 15 inches or so. Below 2 feet from the floor it is absolutely fine. No drainpipes etc outside which could possibly case damp penetration either. The wall are over 2 feet thick anyway and I understand from the local builder that it is actually a cavity wall with the gap between the 2 granite walls staffed with horsehair etc.!!

I have heard of a product called Q19 I think which might be the answer but it is very expensive and before I invest in that I thought I would see if anyone on the forum has any suggestions or indeed experience of dealing with such a problem.

Thanks in advance

Andy

[Gluestick]

Don't know if this helps, Andy?

http://www.drytreat.com/home.asp?pageid=3122D126286B2FA9

http://irc.nrc-cnrc.gc.ca/pubs/cp/wal1_e.html

 

[Andyphilpott]

Thanks Gluestick - although the site does not specifically cover efflorescence it look like they might well know of a product which might work so I will make contact with them.

Regards

Andy