Hi all, I’ve scoured the forums to see if my particular problem is covered elsewhere but no luck, so before doing something I can’t undo I thought it best to ask for proper advice please;
On preparation for re-decorating my lounge recently, I found very slight damp at the base of the wall ends at the patio door reveal. On further investigation the job went well sour; I found the parquet edge band (two tiles wide) lifted easily, coming away with soft crumbly lumps of damp screed. The tiles remained dry presumably thanks to the bitumen they were laid with. Since moving in 23 years ago there’s always been a slight upward incline at the edge band, but it’s never changed so I assumed it was just poor levelling.
The attached pic was taken after initial attempts of a clean out with a shop vac. I then made up a ‘cowbell’ shaped scoop but could only reach down to 2ft deep where the sand had gone from damp & crumbly to almost as wet as bricklaying mortar mix. I’m assuming there should be a poured concrete footings bed at the bottom, but I haven’t been able to reach that deep.
The slab itself is 3” thick, with no evidence of any DPM, and ends flush with the outer face of the inner leaf. It seems reasonably impervious to water compared to the brickwork & screed. The UPVC patio door frame sits on the outer leaf DPC, with its inner edge flush with the brickwork, so leaving a 2.5” wide cavity gap that wasn’t easy to bridge with tiles or some sort of closer. The door opening appears to be original, and not having been modified from french doors with brick ears.
Further inboard from the cavity, the screed is normal strength, dry, and firmly bonded to the slab, as are the parquet tiles, so I’m hoping to keep repairs localised.
On the outside, there’s soil abutting the wall, and topped with patio stones, at 2 bricks clear below DPC. The pointing is not in great condition and the bricks are damp up to DPC level. The soil is clay, but the house is sited at the top of an incline, so not in a soggy soil area.
It’s now been left open for two weeks, and the cavity has dried out quite significantly so it does seem that lack of ventilation is (perhaps one of several) main cause(s). The house only has one air brick, and it’s at head height on the opposite side of the building, but the cavity is filled with poly bead insulation, which I’m thinking may be aggravating the problem, although there never was any ventilation below the door reveal anyway.
On trying to look left & right into the cavity each side, there does seem to be crumbly fill, but not as high as DPC level, so I’m wondering if this is just dropped ‘snots’ accumulated from the bricklaying….or should the outer leaf intentionally be braced below DPC against soil swell pressure? There are 3 brick ties at 1 brick below DPC, and the two not in view in the picture are corroded through, so not stainless steel, which suggests that below DPC shouldn’t be damp. And why should there even be any tension ties if the wall is braced both sides?
I’m not a builder, so I’ve trawled the internet for concrete floor installation details, but all I can find is modern practices, which pay a lot of attention to damp protection, so am left puzzled about why in stark contrast my 1959 built house has almost nothing, and worse still, a sand filled cavity which equates to putting a drinking straw in a glass of drink.
I’m not sure what to do, and have read some info warning against use of chemical damp proofing because blocking one path only means the damp will find another way up.
I’m considering my options, but they’re just best guesses, so any advice appreciated please. Leaving the cavity empty seems preferable, if allowable, or filled with waterproof PU foam.
On preparation for re-decorating my lounge recently, I found very slight damp at the base of the wall ends at the patio door reveal. On further investigation the job went well sour; I found the parquet edge band (two tiles wide) lifted easily, coming away with soft crumbly lumps of damp screed. The tiles remained dry presumably thanks to the bitumen they were laid with. Since moving in 23 years ago there’s always been a slight upward incline at the edge band, but it’s never changed so I assumed it was just poor levelling.
The attached pic was taken after initial attempts of a clean out with a shop vac. I then made up a ‘cowbell’ shaped scoop but could only reach down to 2ft deep where the sand had gone from damp & crumbly to almost as wet as bricklaying mortar mix. I’m assuming there should be a poured concrete footings bed at the bottom, but I haven’t been able to reach that deep.
The slab itself is 3” thick, with no evidence of any DPM, and ends flush with the outer face of the inner leaf. It seems reasonably impervious to water compared to the brickwork & screed. The UPVC patio door frame sits on the outer leaf DPC, with its inner edge flush with the brickwork, so leaving a 2.5” wide cavity gap that wasn’t easy to bridge with tiles or some sort of closer. The door opening appears to be original, and not having been modified from french doors with brick ears.
Further inboard from the cavity, the screed is normal strength, dry, and firmly bonded to the slab, as are the parquet tiles, so I’m hoping to keep repairs localised.
On the outside, there’s soil abutting the wall, and topped with patio stones, at 2 bricks clear below DPC. The pointing is not in great condition and the bricks are damp up to DPC level. The soil is clay, but the house is sited at the top of an incline, so not in a soggy soil area.
It’s now been left open for two weeks, and the cavity has dried out quite significantly so it does seem that lack of ventilation is (perhaps one of several) main cause(s). The house only has one air brick, and it’s at head height on the opposite side of the building, but the cavity is filled with poly bead insulation, which I’m thinking may be aggravating the problem, although there never was any ventilation below the door reveal anyway.
On trying to look left & right into the cavity each side, there does seem to be crumbly fill, but not as high as DPC level, so I’m wondering if this is just dropped ‘snots’ accumulated from the bricklaying….or should the outer leaf intentionally be braced below DPC against soil swell pressure? There are 3 brick ties at 1 brick below DPC, and the two not in view in the picture are corroded through, so not stainless steel, which suggests that below DPC shouldn’t be damp. And why should there even be any tension ties if the wall is braced both sides?
I’m not a builder, so I’ve trawled the internet for concrete floor installation details, but all I can find is modern practices, which pay a lot of attention to damp protection, so am left puzzled about why in stark contrast my 1959 built house has almost nothing, and worse still, a sand filled cavity which equates to putting a drinking straw in a glass of drink.
I’m not sure what to do, and have read some info warning against use of chemical damp proofing because blocking one path only means the damp will find another way up.
