What is causing the damp in these photos?

[mcjizja3]

Hi,

I've recently exposed an old fireplace in a room we are renovating. I had previously noticed a damp patch on the outside of the house on the fireplace wall but didn't quite realiase the extent of the problem until everything was stripped out.

This is the view from inside, as you can see the bricks are crumbling:

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• mcjizja3
• 30 Apr 2012
• 1

And from outside (There is only 1 brick thickness in the wall at the back of the fireplace):

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• mcjizja3
• 30 Apr 2012
• 1

From a distance:

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• mcjizja3
• 30 Apr 2012
• 1

As you can see there is a damp line all the way from the chimney stack down to where it looks to have 'pooled' at the bottom. The chimney pot for this downstairs fireplace is capped, the room above is uncapped (there also seems to be a family of jackdaws in there!). The room above has a blocked fireplace and no vent that I can see. So my initial thoughts were water ingress through the uncapped chimney leaking right down to the DPC?

Before I exposed the fireplace, there was a gas fire using the chimney although this was unused for a few years before we moved in. If any condensation was caused by the gas fire this would have dried out by now, right?

Another suspicion I had was rising damp. The fireplace was filled with bricks, soot, plaster etc and the quarry tiled floor beneath is damp. (We're planning on having an asphalt screed eventually to sort this out) So the old DPC could have been bridged in this location for many years.

We had a new DPC a year ago when we moved in.

Maybe all three factors could have contributed to the problem, and others I haven't thought of?

I want to have work done to rectify things, but after reading so many conflicting opinions and articles I want to make sure I have the right thing done.

Thank you for looking, I hope someone can help.

 

[tim00]

1. What do you propose to do with the open fireplace (s)?
2. How do you know that the fireback is single brick? On the outside of the fireplace cheek, does it measure back 2 x bricks to the back wall?
3. Typical for your conditions would be some penetrating and a little rising damp.
4. If possible, post a pic of the exterior at ground level.
5. Research on here, there's much info ref flue's and stacks and openings.
6. There is a condition called sulpherisation that takes place in unswept and unvented, gable flues. But first, deal with the above Q's 1-5.

 

[tim00]

7. Given the waste on the gable, perhaps carefully examine for weeping leaks, any supplies to the basin etc that the waste serves.

 

[mcjizja3]

1. What do you propose to do with the open fireplace (s)?

We would like to leave it open, just clean it up for now and ideally have a woodburning stove in there eventually, when we can afford to (i'm expetcting chimney to need lining etc). But we are uncovering lots of issues in this room so realise we need to leave our options open and do the 'right' thing in terms of cost/quality/realism.

2. How do you know that the fireback is single brick? On the outside of the fireplace cheek, does it measure back 2 x bricks to the back wall?

The cheek is 2 brick (lengths) yes. The previous occupants have added a window adjacent to the cheek, the width of the wall is clear from looking out of the window. (The interior face of the window is level with the fireback wall, there is a sill over the interior brick face below the window)

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• mcjizja3
• 30 Apr 2012
• 1

3. Typical for your conditions would be some penetrating and a little rising damp.

OK thanks, do you think the uncapped chimney for the room above is a likely culprit?

4. If possible, post a pic of the exterior at ground level.

Here it is:

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• mcjizja3
• 30 Apr 2012
• 1

5. Research on here, there's much info ref flue's and stacks and openings.

Yes, I will continue to, thanks.

6. There is a condition called sulpherisation that takes place in unswept and unvented, gable flues. But first, deal with the above Q's 1-5.

Yes, I was reading about that last night, thanks.

7. Given the waste on the gable, perhaps carefully examine for weeping leaks, any supplies to the basin etc that the waste serves.

It's a condensate discharge pipe for our boiler which was only fitted very recently, so I don't think that's related. The copper one running horizontally is the gas supply.

 

[tim00]

2. Ignore the position of the frame - the gable appears to be a 9" solid wall, which would be appropriate for the built date.
Water might be penetrating thro the frame reveal tight to the c/breast. Spray water on and observe.
Smeared on patch pointing appears to have taken place. Whats required is to rake out to 18mm and re-point in 4-1-1, or 3-1xlime. The original mortar is lime mortar. Replace perished bricks. How far you would want to go is up to you, but cover the area in question.
3. No. Research your options for all flues and terminals in that stack.
7. Of course, i didn't think.

FWIW, I can see what might be historical, exterior, injection holes in the course just above the horizontal gas pipe, but no signs of interior injection holes. Any injection should have taken place in the course just above the solid floor.
AAMOI, does the frame have a lintel supporting the depth of the wall?

 

[mcjizja3]

Firstly thanks for the time you've taken to respond. It's really helpful.

Re: 2. Apologies for my ignorance but I can't see how is isn't single brick thickness, the exterior depth of cheek to window is 19", as is the interior depth of the cheek to fireback. Through the window I can see that the window sits within a single depth of brick. Everywhere else on the wall it is clearly double thickness (i.e. above and below the window). I did think this seemed odd. I wonder if it has been modified at some point.

This leads on to what you mention about the DPC - I suspect that if it isn't double thickness they might have injected into the junk that was filling the fireplace rather than the wall itself.

When we had it done last year, there was a feature fireplace spanning the entire width of the room so the injection was not done from the inside (nor into the cheeks). These are the holes you can see in the joint above the gas pipe. There are holes on the inside, it's just not clear on the photos. They are in the first joint above the floor.

I think I might get Rentokil back out to check this and perhaps to do the cheeks while they are at it.


Great idea about the penetration through the window! The dampness does look to be up against the window. I'll get the hose on it to see.

AAMOI, does the frame have a lintel supporting the depth of the wall?

No it doesn't, only a timber one for the the interior face. We are planning on replacing the window and will have a steel lintel put in when this happens. Could this be contibuting too?

 

[tim00]

2. Perhaps it's only the fireback that is 4.5" - cheeky bricklayers.

3. DPC injection, FWIW, in solid walls is typically "double drilled" from the exterior. Hence, the fireback would have been drilled from the exterior. I can see injection holes in the fireback first course which indicates that they were drilled from outside and burst thro, or were drilled from inside. The cheeks should have been double drilled from the outer face of each cheek - that is, if they were accessible at the time.
Check with Rentokil, will they charge for a return visit and any "make-up" work?

Definitely install steel lintel (s) above any new frame. Doubtful that dropping pressure from lack of a lintel is causing damp. Mind, there is a "crack" ( or pulling away ) down the right hand reveal?

Ref. the floor: i would pull the quarry tiles and see what you've got - come back here at that stage. Research historic solid floors.

 

[joe-90]

It's condensation. You see it all over the UK if you go out and look.

 

[mcjizja3]

The DPC was definitely only done from outside, the interior was inaccessible back then.

When they inject the DPC do they do one injection in the centre of the wall which disperses or do they do a series of injections throughout the width of the wall?

If the latter then it's probably only the cheeks I need to worry about, but if the former then the DPC is probably now in the skip outside!

I'll check when I get home but i don't think that's a crack on the window reveal, just an untidy finish where they've patched up when knocking through and a bit of render I haven't knocked off making it look like one.

Re the floor. I was thinking of pulling the tiles up before we have asphalt put down to keep the floor level similar to the next room. Loads of the tiles are damaged, its really uneven and covered in damp patches. We've already had it done to the rest of the ground floor (except one room which is suspended timber).

 

[^woody^]

If that damp area is in line with the flue, then its sulphate attack of the mortar from the flue gasses - cement eaten away, leaving mainly sand and porous joints

 

[mcjizja3]

OK, so whatever the particular cause(s)....

If I:

-Ensure the DPC is OK.

-Replace the window and ensure it's not allowing water ingress.

-Rake out and repoint all areas where damp is evident using sulphate resisting cement in the mix.

-Replace eroded bricks.

-Allow any condensation to dry by leaving the fireplace open

I should cover all bases?

tim00 - I just lifted a few tiles and it's just sandy earth underneath.

 

[joe-90]

Your're not getting it are you? It's condensation.
Warm moist air from your house is condensing on the cold damp brick. It's not going to dry out, neither will it get any worse - forget about it. Spend your money on a holiday.

 

[mcjizja3]

Spending money unneccesarily is exactly what i'm trying to avoid by posting on this forum, and I'm very grateful for people who know more than me about this subject giving me advice.

At the very worst point of the most eroded brick in the fireback there is probably about an inch of crumbly brick left. This is not something I think i should leave and forget about, even if just for thermal efficiency!

The windows need replacing anyway and we budgeted for this when we bought the house.

The pointing is eroded on that wall and needs doing anyway, I may as well make sure that sulphate resisting cement is used when this happens.

I have had a DPC under guarantee, I may as well make sure it is doing what I paid for it to do.

If, after all this is done nothing has changed. I won't have lost anything, I can put it down to condensation and fly off to Benidorm.

 

[joe-90]

Good idea.

Here's a tip:

It's probably that your floor has no damp membrane and damp is evaporating into your warm house and then condensing, it's like a wick - never ending.

Another tip:

Avoid Benidorm in July.

 

[pred]

In the past i have cured damp in an upstairs bedroom useing Dulux Weathershield, he asked me to quote him for rerendering, there was nothing wrong with what he had, just a bit porous, so if Thomsons waterproofer is as good as what they claim it might relieve your problem a lot quicker and cheaper than other alternatives.