Advice sought on suspected penetrating damp problem

[corumuk67]

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.

Damp problem – Google Drive

drive.google.com

 

[Old Salt]

I am not a builder but some of the brickwork looks as if it could do with being repointed. The down pipe by the conservatory looks as if the joint could be closed up and make sure its clear. The lead of the conservatory looks as if it could be reshaped closer to the wall.

 

[Wayners]

Looks like water isn't running away as I can see puddles.
The ground gets saturated under the slabs then the damp gets in the cavity and property.
Aco drain along the centre taking water away maybe or french drain. Something like that.
You also need to get those slabs away from brickwork with 100mm of gravel.
Then. In the summer apply storm dry to brickwork.
Looks like a very wet and damp area that can be easily be fixed.
Go watch some skillbuilder YouTube videos on the subject for information

 

[corumuk67]

Thanks both for the responses so far, some solid observations there.
I've been in discussion with the neighbour a while ago about getting a drain survey done with cameras, as it certainly looks collapsed in areas. I guess if it is that could also allow water to back up into the drainpipe or flood the surrounding soil even if the drainpipe itself isn't blocked?
Presumably that would also entail excavating between the houses to lay new drainage.

As old salt mentioned the pointing is definitely a bit shabby in places and could probably do with some repairs. I was wondering whether getting the wall rendered would help, but the 'storm dry' sounds like a somewhat cheaper alternative. I'll have to look into that.

Luckily the rain has eased over the last few days and the wet spots on the wall are slowly drying out and fading.

 

[noseall]

Thanks both for the responses so far, some solid observations there.
I've been in discussion with the neighbour a while ago about getting a drain survey done with cameras, as it certainly looks collapsed in areas. I guess if it is that could also allow water to back up into the drainpipe or flood the surrounding soil even if the drainpipe itself isn't blocked?
Presumably that would also entail excavating between the houses to lay new drainage.

As old salt mentioned the pointing is definitely a bit shabby in places and could probably do with some repairs. I was wondering whether getting the wall rendered would help, but the 'storm dry' sounds like a somewhat cheaper alternative. I'll have to look into that.

Luckily the rain has eased over the last few days and the wet spots on the wall are slowly drying out and fading.

See if you can ascertain whether the specific damp spots coincide with the cavity ties.

 

[^woody^]

As an old MOD house, is this a system or traditional build?

The following is based on a traditional build ....

The external wall is getting saturated - the staining at high level. The bricks are soft clay and the unfinished recessed pointing is the wrong choice - it allows water to easily penetrate the joints and the bricks.

Its common, and likely that this saturation is then causing water to run down the back of the external bricks in the cavity and into any mortar snots on tie wires (the random wet circles) and across at the floor level (the larger damp patch).

The black mould may well be related to water cooling the wall, causing a condensation issue.

Remedy - have the cavity opened up (externally) at the damp spots to check for and remove and cavity bridging. Water saturation of the external leaf is not an issue, but cavity bridging is.

In extreme cases of blocked cavities (or poorly fitted insulation that can't be removed) then the external wall may need to be pointed up with a better weather-resistant joint, and maybe a water proofing coating applied.

If there are numerous locations of damp, then a borescope cavity survey may give a better idea of a course of action.

If there are other unrelated patches of black mould elsewhere in other rooms, then there is probably a separate condensation issue and you'll need to check out general information on dealing with excess humidity and condensation related issues.

 

[corumuk67]

Hi Woody, thanks for the detailed response and comments.
Not sure what you mean by a 'system' vs 'traditional' build, but your subsequent observations have pretty much hit the nail on the head I think and the spots that appear part way up the wall and then grow and shrink after heavy rain definitely fit the idea of the water bridging the cavity either via wall ties or something else.

We don't seem to have problems with mould elsewhere in the house, which I try to keep ventilated as much as possible. A spot here or there over the course of 15 years but prompt cleaning and maintaining ventilation seems to prevent it returning (the house does get cold in winter which pushes the humidity up, so I'm always on the look out).

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. Could this be an issue as well contributing to the penetrating damp? 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.