Damp area appeared after plaster previously dried on internal wall

thms

New Member
We're in the middle of an extension and we've had an existing internal walls boarded and skimmed. The plaster dried out initially and all looked good, but now it's gone damp at the bottom on two small sections of internal walls.

Initially the cause was thought to be a leak, but there is no sign of any water. As far as I know there are no pipes in the wall near the damp patch. The old lead pipe does go up into the wall away from this area but there is no sign of water leakage in this area. There was no sign of damp on these walls prior to the building work.

It's a mystery to the builders and me. Can't figure it out. Any help appreciated.

Looking below the damp area, there is a mini-basement area, filled with rubble and the brick below where the damp is worse looks a little damp here. Can't see any sign of a DPM/slate.

Pictures:

  • 1st and 2nd pics - Major damp area which appears having previously drying
  • 3rd pic - This is below this major damp area in the mini-basement/rubble pit
  • 4th pic - Second damp area, around 90 corner to left of major damp area
  • 5th pic - The internal walls prior to boarding and plastering
 

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Last edited:

The Hobo

Well-Known Member
We're in the middle of an extension and we've had an existing internal walls boarded and skimmed. The plaster dried out initially and all looked good, but now it's gone damp at the bottom on two small sections of internal walls.

Initially the cause was thought to be a leak, but there is no sign of any water. As far as I know there are no pipes in the wall near the damp patch. The old lead pipe does go up into the wall away from this area but there is no sign of water leakage in this area. There was no sign of damp on these walls prior to the building work.

It's a mystery to the builders and me. Can't figure it out. Any help appreciated.

Looking below the damp area, there is a mini-basement area, filled with rubble and the brick below where the damp is worse looks a little damp here. Can't see any sign of a DPM/slate.

Pictures:

  • 1st and 2nd pics - Major damp area which appears having previously drying
  • 3rd pic - This is below this major damp area in the mini-basement/rubble pit
  • 4th pic - Second damp area, around 90 corner to left of major damp area
  • 5th pic - The internal walls prior to boarding and plastering
you got a male dog
 

ChrispyUK

Well-Known Member
Correct answer... Dot and dab is for new builds and not refurbishment work.... Just dabbed a lounge at cutomers request but injected it then sand and cement rendered it to 1.2m 1st with added sbr....

funny you should say that. I’ve just done the same (Without the injection) today on my house I’m doing up as external wall is getting insulated PB.
 

ChrispyUK

Well-Known Member
The customer never asked for it but its that quick and the cream is cheap its not worth not doing....

it had been done previously. Walls are bone dry and I’ve dug down to the raft externally, repointed and tanked with Remmers mb 2k. The previous owner had a damp company in 20 yrs ago due to rotten floorboards etc. They replaced all the downstairs timbers, injected, hacked off etc. They never stopped the water coming in under the floor though!!!! Muppets!!!!!
 

brimplas1

Well-Known Member
it had been done previously. Walls are bone dry and I’ve dug down to the raft externally, repointed and tanked with Remmers mb 2k. The previous owner had a damp company in 20 yrs ago due to rotten floorboards etc. They replaced all the downstairs timbers, injected, hacked off etc. They never stopped the water coming in under the floor though!!!! Muppets!!!!!
They did half a job then....lol... My 1st house was the same, bought it in summer and the sub cellar was bone dry.... Come winter it had a foot of standing water...
 

ChrispyUK

Well-Known Member
They did half a job then....lol... My 1st house was the same, bought it in summer and the sub cellar was bone dry.... Come winter it had a foot of standing water...

They did the ‘standard’. Perhaps it was summer when they did the job. When I bought the house, there was water under the floor causing condensation. 20 yr old floorboards rotten again. I believe that this was ‘the issue’ hence the tanking etc. If you’ve got experience with french drains, then I would appreciate some advice as I haven’t back filled yet. PM perhaps?
 

Brimstone

Well-Known Member
Presuming you have somewhere for it to drain to.. big "U" of PM, bit of pebble in bottom and lay perforated drain to falls, fill rest with pebbles to the topcover with a bit more pm and whatever you want to finish with, even soil. PM stops soil/sand etc permeating (?? wha??) running into the stones & holes and blocking up the drainage.
 

brimplas1

Well-Known Member
They did the ‘standard’. Perhaps it was summer when they did the job. When I bought the house, there was water under the floor causing condensation. 20 yr old floorboards rotten again. I believe that this was ‘the issue’ hence the tanking etc. If you’ve got experience with french drains, then I would appreciate some advice as I haven’t back filled yet. PM perhaps?
Im no expert bud, just use common sense ...lol... I was on my arse for money so i dug a hole about 4ft deep, put a plastic bin in the hole with lots of 6mm holes in it and put a sump pump in with a float switch..... I ran the outlet through the kitchen cabinets and out into the drain.... It worked a treat, when it rained i could here it kick in and hum....
 

ChrispyUK

Well-Known Member
Presuming you have somewhere for it to drain to.. big "U" of PM, bit of pebble in bottom and lay perforated drain to falls, fill rest with pebbles to the topcover with a bit more pm and whatever you want to finish with, even soil. PM stops soil/sand etc permeating (?? wha??) running into the stones & holes and blocking up the drainage.

Basucally the plan with landscape fabric around it. Problem is the fall. All drains at back of house. Have set up a site level, and deepest I can get is about half way down my trench. Ideally would be at the base of it.

Would I better be filling whole trench with 20mm gravel, or filling bottom with soil/clay then gravel. My thinking is that, if it’s all gravel, hydrostatic pressure may at least push up water into the pipe.
 

ChrispyUK

Well-Known Member
Im no expert bud, just use common sense ...lol... I was on my arse for money so i dug a hole about 4ft deep, put a plastic bin in the hole with lots of 6mm holes in it and put a sump pump in with a float switch..... I ran the outlet through the kitchen cabinets and out into the drain.... It worked a treat, when it rained i could here it kick in and hum....

me neither mate. Everyday a school day and all that. Like you said...apply some common sense. Helped out in a cellar conversion a few years back and although a commercial product, basically the same as what you did.(y)
 

brimplas1

Well-Known Member
me neither mate. Everyday a school day and all that. Like you said...apply some common sense. Helped out in a cellar conversion a few years back and although a commercial product, basically the same as what you did.(y)
But without wrapping the whole place in plastic and charging 10k...... lol
 

ChrispyUK

Well-Known Member
But without wrapping the whole place in plastic and charging 10k...... lol

Not cheap is it. Can’t remember the rest of the spec, just helped with the sump pump and concreting.

mortgage valuer asked for structural report and timber and damp On mine. I paid for independent experts as I know the usual story reg damp companies and their ‘free’ reports. Couple hundred quid was worth it as I went back and re- haggled the offer we’d put in and got a good few grand off.
 

Brimstone

Well-Known Member
Basucally the plan with landscape fabric around it. Problem is the fall. All drains at back of house. Have set up a site level, and deepest I can get is about half way down my trench. Ideally would be at the base of it.

Would I better be filling whole trench with 20mm gravel, or filling bottom with soil/clay then gravel. My thinking is that, if it’s all gravel, hydrostatic pressure may at least push up water into the pipe.
If its all gravel then it'll migrate or settle out at the level of your drain or come out lower down. Presume there is a slope - one option might be to ignore the drain and dig a big soakaway on the downhil side - one of those milkcrates wrapped in fabric jobbies. Then you'll get the falls etc.
 
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