Time for damp proofing to take effect.

daveo · Post by **daveo** » Wed Jul 15, 2009 12:14 pm

Hi.
I would appreciate some advice on Damp proofing.
I have recently had an extension and internal building work done to my house, this included having some of the internal walls damp proofed. This was carried out by our builder using Dry Zone paste.
This work was carried out 3 weeks ago with the walls re-plastered afterwards. My question is how long should it be before the damp proof course takes effect. My reason for asking is that the dampness was checked on most of the walls before the work started and now most of the walls are giving a good reading indicating that the damp proof course is working. However on a couple of walls the reading are still high indicating dampness is still there. Am I being a little premature in worrying about this so soon?

Also on the corners of one wall there is the edge beading used by the plasterer to give a good straight edge, for some reason the dampness seams to follow this beading quite a way up the wall, is this normal?

Thanks in advance for any advice.

Post by **ultimatehandyman** » Wed Jul 15, 2009 5:32 pm

How long were the walls left to dry out, once the DPC had been installed before they were plastered?

RemedialExpert · Post by **RemedialExpert** » Wed Jul 15, 2009 9:37 pm

Rule of thumb is about an inch a month, so the wall may not be fully protected up to 9 months... just a rough guide.

daveo · Post by **daveo** » Wed Jul 15, 2009 10:09 pm

Hi.
Thanks for the replies.
The walls were left for only a couple of days after the dpc before being re-plastered.

I have just made a quick check and strange as it might seam but the walls at the bottom appear to be dryer than higher up, in some places the intersection between the old and new plaster appear to be the worst place of all, is this normal?

Post by **ultimatehandyman** » Thu Jul 16, 2009 6:52 pm

Take a look at this- damp proofing

An essential requirement of BS6576: 2005 Code of practice for installation of chemical damp-proof courses is to replace wall plaster that has been contaminated by the ground salts deposited by the rising dampness. These ground salts will migrate to the wall surface during the drying out period that follows DPC injection. As the salts are 'hygroscopic' they have a capacity to absorb moisture from the air, especially under humid conditions.