Advice requested in respect of suspected penetrating damp. Damp can be a major issue in the home. Find answers to questions or post your own here.

[corum_uk]

Hi,
We've had occasional problems with what we think is penetrating damp.
This probably isn't a DIY job but I'd appreciate any views/opinions on what might need to be done.
The semi was built around 1969 as part of an MOD estate.
Roof has had new felt, batten and ridge/verge a few years ago.
The damp issue only happens occasionally when persistent heavy rain is driven from the southeast/northeast.
Some years we don't notice any problems inside at all.
Over the last few weeks its been non stop heavy rain from the southeast and the results can be seen in the photo's, with wet patches at various points on the wall, a large wet patch in the centre of the wall at the bottom, and a wet patch near the back door from floor to ceiling.
Pretty sure the drainpipes aren't overflowing, I looked out the other night during a heavy downpour and couldn't see anything overflowing from the top.
That said (see photo), it looks like the drain underground has collapsed, or at least the ground is sunk, but that's a separate issue and has been like it for quite a few years (survey and groundworks no doubt needed).
The most pressing issue is definitely the wet spots appearing inside.
When we first moved in around 2011 and stripped the wallpaper and attempted to paint the wall with a roller, chunks of plaster were coming off on the roller, no doubt as a result of earlier penetrating damp, and we've since had it replastered, although that will probably fall off now as well!
Thanks.
https://drive.google.com/drive/folders/ ... sp=sharing

[stoneyboy]

Hi corum_uk
The damp around the back door will be due to bridging between the inner and outer walls. The problem may be due to the new back door, its frame profile will be narrower than the door it replaced. This reduction in profile may have exposed a narrow strip of the outer brickwork on the inside edge of the frame. Making good the plaster will provide a path for damp. You could check by hacking off a small section of the inner plasterwork, if you see the innner masonry, vertical DPC and a strip of the external bricks then this is your issue.
The damp at low level and the spots on the wall are probably due to snots from when the wall was built being allowed to fall into the cavity. It’s likely that you have a ventilated cavity which is why the -problem appears when the outer wall becomes a]saturated. This is not an easy problem to solve but do not have the cavity insulated because it will make the problem far worse.
Regards S

[corum_uk]

[quote=stoneyboy post_id=135836 time=1770245483 user_id=18922]
This is not an easy problem to solve but do not have the cavity insulated because it will make the problem far worse.
Regards S
[/quote]

Hi, and thanks for the response and insights.

Regarding insulation, these pictures show the cavity under my living room window (window sill is loose at the moment!) with lots of broken down insulation that was presumably pumped into the walls at some point after the house was built. So this could be making things worse? I recall a local plasterer who I've used in the past mentioning that he had branched out into a business that went around removing this type of insulation, at a few grand a pop, but i'm not sure how effective or destructive the process is.

https://drive.google.com/drive/folders/ ... sp=sharing

Someone suggested repointing and a coat of storm dry might help as well?