What to do about a damp wall?

[wiseblood]

I live in a 1920s detached house, last year we started having damp problems in the dining room next to the fireplace (external cavity wall, not insulated) paper coming off, efflorescence on the plaster work. It turned out directly above this was a few missing tiles on the roof, with damaged felt and damaged lead around the chimney breast. I ended up having the whole roof re done and the chimney stack re pointed. We were told that the damp was the water falling though the damaged roof, falling down the cavity, this was highlighted by a damp meter reading high all over the wall internally and that plasterwork wouldn't dry and needed to come off. The exposed bottom bricks were reading 25% on a damp meter, this was 8 weeks ago, the bottom bricks are still reading 25%ish now. (some are 25, some ar 12ish, its all very random)
Ive taken a few floor boards up and there is a damp section on the ground, about 30 cm by 15cm in diameter, next to the chimnet breast, this has been here for about 6 weeks and not changed.

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Ive contacted several damp specialists and only one has turned up, he told me i need the problem was the roof and i need the wall tanking at a cost of £800, not including plaster work.
A plasterer told me that this was all fine and i should just re do the wall in a foil backed plasterboard and it will be ok.
I personally dont see why i need the wall tanking, as this isnt going to cure a problem if there is one.
Im after some advice on if this is still a problem, or if im just being paranoid, as im getting a different answer off everyone i speak to.

Sorry about the long post i hope it all makes sense, and thanks for any help.

 

[dishman]

Is the chimney sealed at the top? Or does it have an open cowl allowing air flow through the chimney. Or at any point are their air bricks which allow air flow through the chimney.

Before you ripped everything down, was the chimney sealed at the bottom?

 

[ree]

You noticed damp conditions 12 months ago. Suddenly?

Do you have any pics of the roof & stack prior to the re-roof? And after?

You have since had a new roof - when did you re-roof?

You still had damp conditions - were they better, same or worse?

What about damp conditions in the room above and in the loft?

Have you had the flues swept?

You removed the plaster and fire surround - when?

What am i looking at through the floorboard - a concrete oversite or a soil oversite? Why did you lift the floor boards?

Is that pipework CH microbore or a gas supply?

Perhaps post pics of the external c/breast and stack, and the elevation wall?

If you use the Search facility on here, & in the roofing forum, & read up on similar subjects you'll notice that chimney stacks & faulty flashing often play significant parts in introducing moisture.

 

[wiseblood]

You noticed damp conditions 12 months ago. Suddenly?

Not suddenly no, we started noticing the paper coming loose at the corner next to the fireplace, it slowly got worse

Do you have any pics of the roof & stack prior to the re-roof? And after?

I can get some later on today of the stack now but not before

You have since had a new roof - when did you re-roof?

Feb/March time

You still had damp conditions - were they better, same or worse?

What about damp conditions in the room above and in the loft?

The room with the damp problems was reading high on a damp meter all over the right hand side of the wall, with the plaster on. The room above was reading 25%+ on the plasterwork. The room above is now reading low teens on the plaster work, so yes there is an improvement generally in the dampness.

Have you had the flues swept?

Yes about four years ago when we changed the fireplace

You removed the plaster and fire surround - when?

About 8 weeks ago

What am i looking at through the floorboard - a concrete oversite or a soil oversite? Why did you lift the floor boards?

It feels like soil.
We lifted the floor board as it was damaged, so I was going to replace it. Not to do with the damp problem.

Is that pipework CH microbore or a gas supply?

Its a gas supply to the fire

Perhaps post pics of the external c/breast and stack, and the elevation wall?

Ill get more pics tonight when i get back from work

If you use the Search facility on here, & in the roofing forum, & read up on similar subjects you'll notice that chimney stacks & faulty flashing often play significant parts in introducing moisture.
I will do thanks, i believe the roofer (wife's uncle) when he says the roof and flashing is sound, he has been up since, to double check and said everything is sound.

Is the chimney sealed at the top? Or does it have an open cowl allowing air flow through the chimney. Or at any point are their air bricks which allow air flow through the chimney.
There is an open cowl at the top, there are air bricks into the room but not on the chimney i don't think


Before you ripped everything down, was the chimney sealed at the bottom?
There was a gas fire in place, used less than 10 times a year.

Thanks for the responses. I've replied to the questions above, and will attach more pictures later on today.

 

[wiseblood]

Here is the pics of my chimney breast from the outside, i dont have access to it, it can be only accessed from my next door neighbors land.

She has built a little wall between the chimney breasts.

The above pic is of the wall where the problem lies.
The four loose bricks are now back in properly, they were taken out to see if the cavity was filled with rubble, which is was slightly but not much (cleared 6 weeks or so ago)

My neighbour had planted plants inbetween the her little wall and my house. We have asked to to remove them, unsure if its done yet.

The red line is where there is a brick wall under the floor boards and the blue patch is where the damp under the floor boards is.

The numbers are the percentages of the bricks on a damp meter (only cheap off amazon, bought for logs but has a brick setting on it)

The rest of the wall is between 5-10% on the bricks.
The damp patch under the floor boards is 23%

The bricks on the outside of the house are also 5-10%

Hope this all makes sense to people.

Cheers

 

[tony1851]

Those so-called 'damp meters' are worse than useless.

 

[wiseblood]

Those so-called 'damp meters' are worse than useless.

To be fair, it gave the same reading as the all singing all dancing one the damp specialists gave.

 

[masona]

http://www.askjeff.co.uk/rising-damp/

 

[ree]

Thank you for the detailed response and the pics. I'm afraid that i cant come to any definite conclusions.

The planters might be bridging the side walls of the c/breast - do you know where your internal and external DPC's are - esp in relation to the flag pathway? The external bottom course of the c/breast is very wet and stained.

When you had the bricks out did you examine up the cavity looking for blockages and snots on cavity ties?

The fender wall is holding soil up to the concrete, or stone, front and back hearths. Moisture could be coming up from this soil infill.

The stack and c/breast pointing look to be in excellent condition.

The lead flashing wasn't done by a leadworker. And given that the roof flattens out at the eaves this flashing could be a problematic area. The lead "flaps" would have to be lifted and checked for capillary moisture.

Are there any signs of staining on the overhang soffit? The tile doesn't appear to be new tile from the last 12 months!

Perhaps the majority of the damp is residual from when roof tiles were missing, and it will slowly dry out - perhaps.

When making good I would render the suspect wall with S&C, dont use gypsum plaster.

I have to go out now - perhaps i can come back to this later.

 

[wiseblood]

When you had the bricks out did you examine up the cavity looking for blockages and snots on cavity ties?
Not with a camera or anything just with what we could reach, we have had a large amount of building work done, the other side of the house got knocked down and that was rather clean

Are there any signs of staining on the overhang soffit? The tile doesn't appear to be new tile from the last 12 months!
The soffit was rotten where the damaged tiles were. We are in a conservation area, so all the roof tiles are reclaimed

Perhaps the majority of the damp is residual from when roof tiles were missing, and it will slowly dry out - perhaps.
We were hoping thins, but thought the patch on the floor would have disappeared by now if this was the case

When making good I would render the suspect wall with S&C.
Whats S&C?

 

[ree]

Maybe the damp seen on the oversite, and the fender wall in the same pic is a combination of residual damp, true rising damp and some penetrating damp.
Do you intend to keep the hearth arrangement as it is?

If you have done with the gas supply then i should have it made redundant at its source tee.

Sort out any wiring or cable runs or outlets at this point in the work.

Sand and cement.

The stack flashing looked like the old flashing re-used - just saying, i dont obviously know for sure.