1901 terrace with unusual damp problem

[drpepe]

1901 stone built house, was originally a semi then around 1913 someone built a house on the other exterior wall - which is about 30 cm higher than our house.

The presumed structure of the 'new' party wall is below (credit to cAtLeYx from the diynot forum for the pic), although it is unknown whether the builders installed a cavity.

A previous owner got a damp company to come in and inject and rerender the party wall from front to back in the hall (not the rear party wall in the kitchen) - however this hasn't worked as you can see below, the damp is coming out of the wall at ~1m where the new damp proof render ends. Also the pink plaster has blown in several places. When I removed the wallpaper, the line of damp is visible across the whole party wall. High humidity (70-80%) in the hall has resulted in green growth on wooden furniture.

The question is what can be done? I can't change the lay of the land, or my neighbour's house. Replacing with lime to allow the damp to breathe from the wall would appear to me to be a non starter as the source of the damp will not be removed. The past 2 years have been spent digging out the damp muddy subfloor in the hall, dining room & front room and installing more airbricks. I currently have the builders in for a rear extension, and having removed the kitchen units, the builder has suggested vandex coating the wall before installing the new kitchen. I am a little sceptical as a (similar??) treatment has clearly failed to some extent in the hallway. What i don;t want is to install the kitchen and in 6 months time the cupboards smell of musty damp...


Any advice would be greatly appreciated.

 

[malcolm]

It's worth asking your neighbour if they have any damp in their side of the wall. The damp seems to go very high up your side of the wall. If you both have a problem it could indicate a water source such as a leaky pipe that needs to be dealt with.

From what has happened so far a perfect waterproof coating on the wall seems likely to transfer the problem to floor and ceiling joists and to the neighbours.

I would be keen to find out a little more about the construction. Just measuring the wall thickness would give you a clue. A gap in the plaster at the appropriate point covered by a taller than normal skirting board might be enough to stop the water sucking up if the problem is simply as described in your image.

 

[drpepe]

It's worth asking your neighbour if they have any damp in their side of the wall. The damp seems to go very high up your side of the wall. If you both have a problem it could indicate a water source such as a leaky pipe that needs to be dealt with.

From what has happened so far a perfect waterproof coating on the wall seems likely to transfer the problem to floor and ceiling joists and to the neighbours.

I would be keen to find out a little more about the construction. Just measuring the wall thickness would give you a clue. A gap in the plaster at the appropriate point covered by a taller than normal skirting board might be enough to stop the water sucking up if the problem is simply as described in your image.

Hi there - yes i do know he has had a damp company in to look at his hallway (on the party wall) - this was within the last couple years. The treatment in our hall was probably 4 years ago, and I also know our house has had at least 2 rounds of chemical DPC at the front wall (see below) - god knows how many times over the years the party wall has been done ...

COuld you explain what you mean by your last paragraph - what would be useful to know about the construction and what exactly do yo mean about the gap/tall skirting?

 

[Feltwell]

I'm surprised the builders bothered to build a new wall on your neighbours side - that they didn't just turn the outside of the original wall into the inside wall surface of the new house.

If you're certain that a new wall was built, given that you don't know the construction detail between the 2 houses, I'd take some plaster off and remove a couple of bricks and see what lies behind. An endoscope would of course be the perfect tool to see in through the gap, but to start with a digital camera or phone with flash poked through the hole may show some detail.

If there is a cavity and you want to see further in then someone who does drainage surveys might be an option.

Simple question, but what is the joint like at roof level between the houses? Is there a possibility that water is getting in there and travelling down a cavity?

 

[Matt Green]

No DPC, chemical or otherwise, is going to function in that wall; it will be bridged by your internal plaster.

I would assume the wall is solid or functions as a solid wall at ground level and consider a lining system (Delta/Triton/Others exist). If you are more of a purist, then isolated timber battens and a lath and plaster internal finish would achieve the same thing.

Malcolm's comment about the skirting relates to the fact that plaster should never be continued into contact with the floor, a gap of at least 50mm should be left to prevent water moving from beneath the floor into the wall plaster. The skirting hides the gap and the taller the skirting, the bigger the gap can be and the more water will evaporate behind it. It's a a good suggestion, but I think from the sound of it, that section of wall is earth retaining to 300mm so it may make no difference in this case.

M.

 

[malcolm]

I've got an internal wall that has blown it's paint off due to damp. In my case the plaster extended all the way to a concrete floor. Bricks and stone aren't good at sucking water up from the floor, but plaster will suck water up like mad. The trick there will be to hack the bottom couple of inches of plaster off and cover with a skirting board. The same sort of thing might work a little higher up on your wall if you think the water is getting in at a higher level.

Never trust the damp companies. Have a read of http://www.heritage-house.org/ for a better way of dealing with damp. The videos are excellent.

 

[drpepe]

I'm surprised the builders bothered to build a new wall on your neighbours side - that they didn't just turn the outside of the original wall into the inside wall surface of the new house.

If you're certain that a new wall was built, given that you don't know the construction detail between the 2 houses, I'd take some plaster off and remove a couple of bricks and see what lies behind. An endoscope would of course be the perfect tool to see in through the gap, but to start with a digital camera or phone with flash poked through the hole may show some detail.

If there is a cavity and you want to see further in then someone who does drainage surveys might be an option.

Simple question, but what is the joint like at roof level between the houses? Is there a possibility that water is getting in there and travelling down a cavity?

Hi - thanks for the comments. I am absolutely not sure that the construction is as the diagram above - it is purely assumed I'm afraid. They may well have just used the existing wall, and there may actually be a cavity. In fact I can investigate this when i visit the house (we have moved out while renovation works are ongoing), by looking at the construction of the blocked up apertures in that party wall that used to be windows and doors (these are alcoves in the party wall as it stands e.g. the book shelves in the first picture used to be an external window).

I could knock out a brick to investigate if a cavity exists - it may be full of debris bridging the gap.

I think the roof is sound - next door's roof overhangs ours a little and the detailing seems adequate to me.

Thanks for the clarification re: skirting - we have tall skirting (25-30cm), and the plaster does not go down to floor level.

Heritage house is a good read, thanks. The youtube videos are certainly an eye opener to the chemical industry...

 

[Zebra]

My thought also was to excavate a couple of bricks to see what is going on. You may be wise to advise your neighbour of what you are doing. It would perhaps even be a legal requirement under the Party Wall Act. Have a read of the Party Wall Act explanatory booklet, it's not quite such a dull read as it sounds.
http://www.planningportal.gov.uk/buildingregulations/buildingpolicyandlegislation/currentlegislation/partywallact

 

[bobby spray]

Sage advice from the posters above. having experienced something similar myself, i removed a couple of bricks to find a blocked cavity. Unfortunately not blocked with rubble but with concrete 'snots' after the building of an extension. had to resort to firearms to remove !