DIY Doctor UK DIY Forums

Hi I was hoping that someone could help answer a question. I have previously addressed a damp problem in an old building by removing the debris collected in the cavity. I am now embarking on a new project and once again have a damp issue, it appears to be the same type of damp however I have a concern about going into the cavity as this building has cavity wall insulation. Can someone tell me the best way to resolve this problem, and if it is advisable/sensible to open the wall to gain access to the cavity? The only other thing that is concerning me is that the damp appears to have spread from an outside wall around to a chimney breast, could this have spread or is it likely to be two sets of damp joined (one from the outside wall and one from water running down the chimney)?

Thanks for your help.

you wont have cavity wall insulation in the chimney brest,It could be penitrating damp or a flashing problem,or something else.
For the cavity problem,I suggest hiring a borescope (fibre optic camera) drilling the wall and checking where the damp is coming in.

Thanks for the advice, I have since been up on the roof and it does look like there could be an issue with the chimney flashing. On the use of the boroscope for the other outside walls would I be able to see anything if there is either insulation or debris in the cavity? If I do have penetrating damp and have to remove bricks what if any issues can I expect from the insulation? Thanks again for your help.

your chimney brest exterior is either face brick or render finish,If its face brick check for any cracks in the mortar and repoint the mortar.Then spray a clear silicone solution like aquaseal over the entire area.
If its rendered tap the wall with a hammer,if it sounds hollow it needs hacking off and re- rendering
With the borescope you should be able to see if the wall ties are covered in mortar,this is usually the case for damp patches shown on the plaster inside the property.
Knocking off the mortar will solve the problem,some of the insulation will fall out on removal of the bricks just stuff it back in.

That's perfect mate, thanks for your help.
I'll start that at the weekend.
Thanks again, Matt

Help?, 100 year old terraced house, injected damp course put in 2 years ago, one small area (3ft) still damp so plaster hacked off to 1 mtr wall dried, and re plastered. 3 weeks later complete area of new plaster wet.
WHY?
Further info, next door is empty and cold
condensation is apparent in room as new insulation, and double gazing put in.
Could any one offer a solution please?

I suggest fitting an air vent with a sliding hit and miss vent on the inside.And or fit trickle vents to the windows