damp problems

3 Dec 2006
Reaction score
United Kingdom
I understand that installing cavity wall insulation can lead to damp problems I'm wondering if cavity wall insulation can cause the following damp problem
On the south east corner of my detached house at the dpc level and slightly below I have a damp patch it extends for approx 6 bricks horizontally and up to 3 bricks vertically but there is no apparent damp inside.I'm assuming that the dpc has been laid properly as the house is now 30 years old and this never appeared until the cavity wall insulation was installed.
Any comments would be appreciated
Sponsored Links
Give the insulation guys a ring explaining prob. they should be able to send a surveyor out to check in case their work has filled lower cavity below DPC or similar.
Thanks for the reply
I am now totally confused I thought that c/w insulation was blown in through holes drilled in the outer wall and would be forced everywhere in the cavity unless a barrier stopped this from occurring. The only way that I can see a barrier being installed is to either drill holes below the dpc or remove enough bricks to put a physical barrier in the way.
What normally stops this from happening
Thanks again
I`m not say it is the problem and indeed may be acceptable, but as you said the damp in this area only occured after the insul. then maybe thats where you start the investigation.
As its only showing on outer skin and below DPC it may not be an issue, thats what DPCs are for. Peace of mind may come from a visit by a survey guy with a cavity probe/camera.(not a medical term) :rolleyes:
The reason behind my first thought was that the cavity should be filled with weak mix concrete 2/3course below DPC. If for whatever reason the cavity is subject to filling this lower area with rain, then if blown insul has dropped into it ,then it would act as a wick and pull up thus soaking wall.
A trial hole in outer skin 2 course down at damp area might show water in cavity or not.
Sponsored Links
External walls won't dry out as quick once CWI has been installed, as there is less heat getting to them from inside. This sometimes causes the bricks to spall with the freeze/thaw cycles.
As the CWI has filled the cavity you've actually lost some air space for the circulation of moisture in the cavity. Water that drains down the cavity usually ends up at DPC/cavity tray/cavity fill and is discharged out through the weepholes but filling the cavity may have resulted in water ponding and/or condensing in the now limited space in the cavity.

Have the weepholes been checked to see they haven't been blocked with the insulation?

If there's no route out this could explain
Hi Thanks for all the replies
I've been thinking about this occurrence since reading these and have concluded that I will drill a 11/2" hole below the damp patch and fit a plastic ventilation plug and await developments it may cure the problem you never know.
post note the surveyor used an endoscope to examine all cavities before the installation of the insulation

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local