Rising damp does not exist (continued; not a sequel)

[Lower]

Quarry tiles in older houses were often set on the bare earth. The tiles are approx 2 inches thick and impervious to water and actually formed the damp proof course.

'ello 'ello 'ello - what's all this then? Earth/ash base?'

I wasn't aware that you could use a brick as a damp proof course.
Are you sure this is what you meant?

Yep. the damp proof course internally in comprised of a blue brick course with a layer of slate.

When you laid the screed, I hope that there was, or that you installed, a damp proof membrane!

yes. i did.

At what height is the thing you're calling a damp proof course (a) in relation to the finished floor surface, and (b) in relation to the DPC in the external walls?

the damp proof course in this internal wall is approx 1 brick above the floor level, and one brick higher than the external damp proof course. However, the external damp proof course is 2 bricks high so it ties in with the internal walls in terms of level. However, the area of damp is a long way from any external walls.

 

[Softus]

Quarry tiles in older houses were often set on the bare earth. The tiles are approx 2 inches thick and impervious to water and actually formed the damp proof course.

Mmm, well, ok, but it wouldn't be a very good substitute for a damp proof membrane because you can't make it contiguous with the wall DPC.

I wasn't aware that you could use a brick as a damp proof course.
Are you sure this is what you meant?

Yep. the damp proof course internally in comprised of a blue brick course with a layer of slate.

OK - I've learned something.

When you laid the screed, I hope that there was, or that you installed, a damp proof membrane!

yes. i did.

OK, and did that membrane overlap with the wall DPC?

the damp proof course in this internal wall is approx 1 brick above the floor level, and one brick higher than the external damp proof course.

At that height I can't see what purpose it serves.

However, the external damp proof course is 2 bricks high so it ties in with the internal walls in terms of level. However, the area of damp is a long way from any external walls.

Turning to those outside walls, are they rendered on the outside and/or plastered on the inside?

BTW, what definition of "long" are you using in the above measurement?

 

[Lower]

Mmm, well, ok, but it wouldn't be a very good substitute for a damp proof membrane because you can't make it contiguous with the wall DPC.

the floor level is acutally below the level of the damp proof course, so that isn't an issue.

OK, and did that membrane overlap with the wall DPC?

again, the floor level is below the damp proof course.

the damp proof course in this internal wall is approx 1 brick above the floor level, and one brick higher than the external damp proof course.
At that height I can't see what purpose it serves.

i've explained that badly. Imagine a damp proof course of bricks 2 layers thick running around all the external walls. The damp proof course on the internal walls is only one brick thick. It is effectively the top layer only of the external 2 brick high damp proof course.

However, the external damp proof course is 2 bricks high so it ties in with the internal walls in terms of level. However, the area of damp is a long way from any external walls.
Turning to those outside walls, are they rendered on the outside and/or plastered on the inside?

the external walls are misture of rendered and unrendered. But the rendering only starts one brick above the level of the blue brick. the closest wall to the damp area is not rendered.

BTW, what definition of "long" are you using in the above measurement?

the nearest bit if external wall that has any direct contact with the damp wall is approx 5 meters from the damp area.

my take on the situation is that the slate damp proof course has failed, and damp is rising within the wall. i can see no other explanation for where the damp patch is coming from.

 

[Softus]

the floor level is acutally below the level of the damp proof course, so that isn't an issue.
.
.

OK, and did that membrane overlap with the wall DPC?

again, the floor level is below the damp proof course.

Um, in all other circumstances I would regard a floor being below the DPC as being quite a big issue, so we might have our wires crossed here.

Imagine a damp proof course of bricks 2 layers thick running around all the external walls. The damp proof course on the internal walls is only one brick thick. It is effectively the top layer only of the external 2 brick high damp proof course.

I understand. No problem here, caveat the other points that we're discussing.

However, the area of damp is a long way from any external walls.

Turning to those outside walls, are they rendered on the outside and/or plastered on the inside?

the external walls are misture of rendered and unrendered. But the rendering only starts one brick above the level of the blue brick. the closest wall to the damp area is not rendered.

BTW, what definition of "long" are you using in the above measurement?

the nearest bit if external wall that has any direct contact with the damp wall is approx 5 meters from the damp area.

OK - no reason to think the damp is coming from there then.

my take on the situation is that the slate damp proof course has failed, and damp is rising within the wall. i can see no other explanation for where the damp patch is coming from.

Leaving aside whether or not the DPC has failed, at the moment I can't see any explanation other than damp rising in the wall.

So, this appears to be my Holy Grail. If so, you should be able to take core samples from each brick course that's below the damp area and find them getting progressively drier in proportion to distance off the ground. If the measurements indicate this, then the damp must be rising, if not then it remains inconclusive.

Turning to the remedy, what options, if any, are you considering?

 

[JohnD]

...So, this appears to be my Holy Grail. ..

Lower, I recommend you buy a Tour Guide's hat and get some tickets printed.

 

[Lower]

the floor level is acutally below the level of the damp proof course, so that isn't an issue.
.
.

OK, and did that membrane overlap with the wall DPC?

again, the floor level is below the damp proof course.

Um, in all other circumstances I would regard a floor being below the DPC as being quite a big issue, so we might have our wires crossed here.

Imagine a damp proof course of bricks 2 layers thick running around all the external walls. The damp proof course on the internal walls is only one brick thick. It is effectively the top layer only of the external 2 brick high damp proof course.

I understand. No problem here, caveat the other points that we're discussing.

However, the area of damp is a long way from any external walls.

Turning to those outside walls, are they rendered on the outside and/or plastered on the inside?

the external walls are misture of rendered and unrendered. But the rendering only starts one brick above the level of the blue brick. the closest wall to the damp area is not rendered.

BTW, what definition of "long" are you using in the above measurement?

the nearest bit if external wall that has any direct contact with the damp wall is approx 5 meters from the damp area.

OK - no reason to think the damp is coming from there then.

my take on the situation is that the slate damp proof course has failed, and damp is rising within the wall. i can see no other explanation for where the damp patch is coming from.

Leaving aside whether or not the DPC has failed, at the moment I can't see any explanation other than damp rising in the wall.

So, this appears to be my Holy Grail. If so, you should be able to take core samples from each brick course that's below the damp area and find them getting progressively drier in proportion to distance off the ground. If the measurements indicate this, then the damp must be rising, if not then it remains inconclusive.

Turning to the remedy, what options, if any, are you considering?

At the moment, i don't have a solution. The wall is damp, but not streaming with water or with salts forming on it. There is a triangular area where you can see the dampness on the wall but i shall probably just skim it, paint it with anti damp paint, and emulsion over the top.

 

[JohnD]

... There is a triangular area where you can see the dampness on the wall ...

Is it a cavity wall, or solid? Does the triangle have point upwards and a flat side downwards?

Sorry my mistake about the cavity:

The wall is only one brick thick so no cavity.

 

[Softus]

So, this appears to be my Holy Grail.

...i shall probably just skim it, paint it with anti damp paint, and emulsion over the top.

Can I come and see it first?

 

[Lower]

when i get the paper off so it can be seen more clearly, i'll take some photos first.

 

[Softus]

I look forward to it.

 

[ModernMaterials]

Softus you typed this...

"I wasn't aware that you could use a brick as a damp proof course."

Of course you meant bricks in the plural, obviously one brick isnt going to do much...

Isnt this the whole basis of this thread? whether bricks require a damp proofing? Im still keeping an open mind.

I know for a fact that class 'a' engineering bricks aka 'blues' take on less water than commons or class 'b's and until recently were the only 'damp proof course' in common use...The question is still wether it is required at all...

electrical conductivity now there's a way forward

 

[Softus]

Hm. I've seen a lot of slate being used as a DPC.

Regarding the plural of brick, I can confirm that you got it right.

 

[noseall]

Hm. I've seen a lot of slate being used as a DPC.

double slate bed dpc's are very common in pre war buildings.

 

[Softus]

In which case I can but assume that I've been looking at a lot of pre-war buildings, and that ModernMaterials hasn't.

 

[ModernMaterials]

(trying very hard not to giggle)...which war?