Penetrating damp?

Tigger90 · 21 Dec 2019

I have a 140year old solid granite wall, rendered on the outside with no damp proof course. The floor joists were removed and the whole room was taken back to bare granite and brick 5 years ago. A new solid concrete/insulation floor was installed. I do not use this room very much and have the radiator on low.
I have noticed the moisture patches on the wall have got larger the last month or so.
Would you say I have penetrating damp?

Notch7 · 22 Dec 2019

If the walls were plastered with standard 2 coat gypsum, ie bonding and multi, it would quickly absorb any damp coming through the wall.
Gypsum is hygroscopic and wicks damp quickly.

I would say that is damp coming through from the wall.

bobasd · 22 Dec 2019

the projection appears to be a redundant chimney breast - thats been blocked up without a flue vent.
flues must be through vented from bottom to top.
the stains and rusting corner beads are probably due to the flue not having been swept before being blocked off.

when the concrete floor was installed was a membrane (DPM) also installed? when you remove the c/breast skirting from (all three sides of) the c/breast you should see a few inches of membrane.
how high is the ground outside the back wall?

knock off all the stained plaster to the front and sides of the c/breast, and cut the angle bead at a height of about 300mm above the last signs of damage.
carefully inspect the two return wall panels & skirting below the window boards.
open up the old fireplace opening and clean out all debris and soot from the surrounds - then sweep the flue. what's the state of any other flues in the house?

to make good: use a 4:1 or 3:1 lime render mix with a limelite skim. and plastic angle beads.

JohnD · 22 Dec 2019

when the wooden floor was removed and replaced with concrete, was it because of damp and rot damage?

do you see such damp on other walls, or just on the chimneybreast?

Ventilating the chimney may do the trick, if the ventilation can dry out the moisture faster than it arrives. Unventilated chimneys get internal condensation, but your wet is low down. When you open up the old fireplace, dig out all the old rubble that the builders threw in there, and it may help to dig out below the old hearth. You may find that's where the damp is coming from. With the rest of the floor sealed and unventilated, there's nowhere else for any damp to go.

Have a look at the outside of that wall in case there is e.g. paving or ground allowing water to pool or run towards the wall, or a dripping gutter or leaking downpipe. I have no experience of granite but I believe it is not absorbent so your damp will be travelling in plaster, render, and brickwork or rubble used on the middle or inside face of the wall. If there is any possibility of an old pipe under the floor or in the chimneybreast, suspect leakage.

Tigger90 · 22 Dec 2019

Notch7 said:
If the walls were plastered with standard 2 coat gypsum, ie bonding and multi, it would quickly absorb any damp coming through the wall.
Gypsum is hygroscopic and wicks damp quickly.

I would say that is damp coming through from the wall.

Thanks.
Yes, there was 2 layers to the plastering or maybe 3? I can remember that it was a greyish colour and then the pink plaster.

Tigger90 · 22 Dec 2019

bobasd said:
the projection appears to be a redundant chimney breast - thats been blocked up without a flue vent.
flues must be through vented from bottom to top.
the stains and rusting corner beads are probably due to the flue not having been swept before being blocked off.

when the concrete floor was installed was a membrane (DPM) also installed? when you remove the c/breast skirting from (all three sides of) the c/breast you should see a few inches of membrane.
how high is the ground outside the back wall?

knock off all the stained plaster to the front and sides of the c/breast, and cut the angle bead at a height of about 300mm above the last signs of damage.
carefully inspect the two return wall panels & skirting below the window boards.
open up the old fireplace opening and clean out all debris and soot from the surrounds - then sweep the flue. what's the state of any other flues in the house?

to make good: use a 4:1 or 3:1 lime render mix with a limelite skim. and plastic angle beads.

Thanks.
This is the wall between 2 windows there has never been a chimney breast on this wall. The chimney is on the other wall which has a stove fitted.
It is only this portion of the wall that’s has an issue. There is no damp on the window reveals.
Yes, the floor did have the DPM fitted and it does go up behind the skirting.
The top of the outside level is 7 inches lower than the inside flooring level.
The corner beads have lightweight curtains in front of them, they are never drawn as I have blinds and the curtains are just for decoration!

Tigger90 · 22 Dec 2019

JohnD said:
when the wooden floor was removed and replaced with concrete, was it because of damp and rot damage?

do you see such damp on other walls, or just on the chimneybreast?

Ventilating the chimney may do the trick, if the ventilation can dry out the moisture faster than it arrives. Unventilated chimneys get internal condensation, but your wet is low down. When you open up the old fireplace, dig out all the old rubble that the builders threw in there, and it may help to dig out below the old hearth. You may find that's where the damp is coming from. With the rest of the floor sealed and unventilated, there's nowhere else for any damp to go.

Have a look at the outside of that wall in case there is e.g. paving or ground allowing water to pool or run towards the wall, or a dripping gutter or leaking downpipe. I have no experience of granite but I believe it is not absorbent so your damp will be travelling in plaster, render, and brickwork or rubble used on the middle or inside face of the wall. If there is any possibility of an old pipe under the floor or in the chimneybreast, suspect leakage.

Thanks
The floor was replaced as I wanted a wooden floor fitted and when the carpet was lifted we noticed the front wall where the windows and where this issue is, the joists were bouncing. After looking, the joists were just on slate and they had rotted at that end.
The outside level is lower and it’s a gravel driveway but I do have really old metal gutters they must be the same age as the house. The roof is new, well 10 years old now!

JohnD · 22 Dec 2019

Tigger90 said:
This is the wall between 2 windows

It would be interesting to see some photos of this wall from the outside.

I'd be looking for a source of water, such as a drain or downpipe.

bobasd · 22 Dec 2019

you say that its a nib from an old outer wall - a wall that would have been over a metre wide?
whats above it, a room or a loft?

given "its the only portion of the wall that has this issue" implies that it could be a rising damp from under the nib thats causing the issues, not damp penetrating from the outside wall.

the problem with my argument is the strange arrangement of windows on either side of the wall nib or whatever it is? why would a c/breast be smack between two windows?

whatever, the present plaster, and corner beads, and skirting will have to be removed as described above.
when the plaster is off the exposed surface will tell us more.
stone walls of that thickness would have been filled with random rubble and even earth.

unless its the photo, the skirting on the face of the wall seems to be showing signs of decay.
the "corner beads" i mentioned are Angle Beads on the outside corners of the wall - google them.

Nige F · 22 Dec 2019

Tigger90 said:
Would you say I have penetrating damp?

No, rising.

Tigger90 · 22 Dec 2019

bobasd said:
you say that its a nib from an old outer wall - a wall that would have been over a metre wide?
whats above it, a room or a loft?

given "its the only portion of the wall that has this issue" implies that it could be a rising damp from under the nib thats causing the issues, not damp penetrating from the outside wall.

the problem with my argument is the strange arrangement of windows on either side of the wall nib or whatever it is? why would a c/breast be smack between two windows?

whatever, the present plaster, and corner beads, and skirting will have to be removed as described above.
when the plaster is off the exposed surface will tell us more.
stone walls of that thickness would have been filled with random rubble and even earth.

unless its the photo, the skirting on the face of the wall seems to be showing signs of decay.
the "corner beads" i mentioned are Angle Beads on the outside corners of the wall - google them.

I had to google nib wall and I don’t believe this is a nib wall. The wall is 20 thick in places and where the windows are it’s about 8 inches.
The chimney is not on this wall and never has been, this is a normal building style for the Guernsey cottages we have here.
As it’s Christmas I won’t be removing the plaster at the moment!
Above is a bedroom in the roof space.
I went and checked the gutters this afternoon and they were full of moss so I have removed that and the other debris.

Tigger90 · 22 Dec 2019

For context I am stood in the doorway and to the right is the window wall and the chimney wall opposite the doorway.

bobasd · 23 Dec 2019

your first post pic showed a projection but having no context my assumption was that the projection was a c/breast (or a nib at right angels to your outside wall).
now, your last two pics show that its obviously not a c/breast - simply put, it's simply a short panel of the outside wall with a recess to each window on either side - showing or explaining that in your first post would have helped.

foxhole · 24 Dec 2019

Good chance the bottom of windows are poorly sealed allowing in moisture .

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Penetrating damp?

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