Damp - coal shed wall under stairs

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Hi all,

I have posted once about floorboards and damp (which is now getting sorted) thanks to some great advice here.

We are renovating our 1930s semi which we've just moved into. We have a patch of damp on an adjoining wall to our coal shed. This is under our stairs. I've tried to attach photos showing the damp plus the coal shed wall this correlates to the other side. The damp isn't mould, but is tacky and damp plaster.

I have done some googling and feel this could be rectified by removing the plaster down to brick, putting a dimpled membrane on the wall, battens, and insulated celotex/kingspan plasterboard, before replastering.

My only concern is with the coal shed wall. Its flaking, there is residue, and I think its pretty humid in there. Would a stormdry masonry cream be appropriate to apply on this?

If I'm totally wrong and need to do something else, I'm happy for all advice given. We are total renovation novices, but enjoy learning as we go. Many thanks.
 

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Actually, I'm thinking to be doing what I've just suggested the coal shed wall side. Limit the interior mess and insulate the coal shed that's under the stairs. Plaster will probably need removing still...
 
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the water is coming from somewhere.

The amount of water in the wall is quite considerable, so it may well be a plumbing leak. A high pressure water main can have a tiny pinhole you can't see, but the fine spray of water will drench a wall over time. Most leaks are more visible.

rather than hiding it, find out where it is coming from. I think either the outside wall, or the floor.

I think your waste pipe has been dripping on the floor. The wet patch is so close that it must be the first suspect.

If not, have a look at the outside. Is there missing flashing, or a defect allowing rain to run down the wall? Or a faulty gutter or downpipe? Is there a drain or gulley in the ground? Is earth or damp coal piled up adainst the wall? is anything bridging the damp course?

Is the indoor floor concrete?

Does a water pipe run under the floor?

The plumbing and taped-up hosepipe look awful.
 
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Thank you for your reply John.

We've only been in the new house for 3 weeks but this is our main priority at the moment.

The waste pipe is definitely dry. The wet patch you can see is a shadow I think.

Everything outside, guttering, downpipe, etc is sound.

The coal shed is strange. We had one in our previous 1930s semi without issue. The bricks/wall in this one have deteriorated more. Salts are present and they feel damp to the touch.

The floor of the coal shed is concrete and inside we have a tiled floor (unsure what is underneath this) and a wooden staircase.

Further investigation of the coal shed and there's a hole in one of the bricks that goes straight through to inside the house. It's tiny but you can see it in the middle(ish) of the coal shed wall photo. It has been clogged with tissue?! Goodness knows what whoever did this was thinking!

The taped up hosepipe can be untaped. It's connected to a tap (not dripping). Presume the previous owner did this.

Unsure of a waterpipe under the floor. Will need to investigate this.
 
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youve got rising damp. you might have penetrating damp as well.lift the vinyl and have a look what condition the floor is in.
 
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Thanks both. The floor is dry as a bone but loads of salts on the coal shed brick wall. Lino has been removed now. The damp is actually drying out a little inside which makes me think penetrating damp? Maybe condensation too as the coal shed is not well ventilated.
 
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youve got rising damp, why else would the damp blow off the face of bricks and show up inside near the stairs?
conensation doesnt penetrate brick walls.
 
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we dont know which bed your dpc is in?i dont know if its a cavity or a solid wall, id guess its a cavity wall. a cavity could be blocked so youd need to open a few bricks above any DPC in the coal hole to see. inside knock off the damagedplaster and make good with a render. in the coal hole clean off the bricks.
 
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Definitely a solid wall.

And it's an internal wall. It's the inner wall of the coal shed that adjoins under the stairs, so no dpc, I don't think.
 
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what year was your house built?

what town or city is it in or near?

In London (as then was) DPC became compulsory in 1875. other towns may differ.

Go and look at your back and your front doorstep. The dpc can often be seen here. usually a thicker bed of mortar with two black lines which are strips of slate. sometimes metal or bitumen or felt. It will be two or three courses of bricks above where ground level used to be when the house was built. Once you have found it, mark it with chalk. It will be the same height all round the house. Airbricks will be at about the same height.

Numbskulls like to hide the DPC with render, or build paving up above it. This causes damp because it bridges the DPC. The remedy is to remove whatever is on it.
 
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Derby, built 1932. Neighbours also have similar damp issues.

Cannot see evidence of a dpc. Dehumidifier currently running in the coal shed.
 
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are you saying the wall is a spandrel wall? thats a triangle walldoing nothing but supporting the stairs?
then whats the wall showing interior damage in your pic, is that an outside wall?
The wall withthe stretcher brick bonding cannot be an outside wall because you say its a 4"solid wall.
You find any dpc by digging at the beds with a screwdriver.
the humidifier isnt needed.
 
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