All about Chimnees... Please!

(Hilary Jane Dunk) #1

Chimney sweep came and did a good job and gave me the certificate to prove it. So far so good....All part of getting ready to buy & install my new Burley 12 kw woodburning stove......But unfortunately an exterior inspection, up a ladder and via binoculars, confirmed my fears that the stack had developed a 'lean'.

Through the binos, it was easy to see a certain amount of crumbly brickwork (though the house itself is stone), and at about the eighth course of bricks, a distinct lean, (outwards away from the house, thankfully), could be seen. Although apart from this(I can here the laughter), it doesn't look too bad.

"Il est dangereuse..".so it must be fixed asap. The sweep suggested that it could be partially dismantled and then instead of building it up again a tubular section could be inserted....He was not interested in doing the work himself or installing my flue for the wood burner , as the roof on this old maison from the 1920's is quite high(as is the stack) and the sweep has said that it would need someone with access to a "cherry picker".

I would be grateful if anyone with expertise in this area, could give me any idea of how much this is likely to cost ? Obviously, I need to get estimates...but what did they charge you for this ?

Answers asap please,Thanks.

(John Withall) #2

"but 'red' placo (plasterboard) specifically designed for the job is frequently used".

The words specifically designed are a bit misleading, Red placo (fireline) is used to resist the passage of fire in a burning building and not long term in a chimney situation and also the condensation and humidity would in most cases cause it to sag after a while.

It sounds like Hilary has the register plate already as part of the kit? presumably in steel.

(John Snell) #3

Hi Hilary,

The sheet material used to close the chimney / flue void around the exit pipe is called a 'register plate' and it should fit snugly to all sides of the original opening. It must be heat-resistant (obviously!) - but 'red' placo (plasterboard) specifically designed for the job is frequently used.

A layer of faced insulation material (heat / fire resistant) is often, but not always, laid on top of the register plate, and this is designed to restrict heat-loss. It's cheap to buy in small panels from any hardware shop and is intended to save you money. In practice, this small mattress of insulation softens the impact of the inevitable bits of old mortar which tumble down the chimney. Make sure you buy the right stuff and not 'ordinary' insulation!

What you're trying to do is to stop heat-loss (waste) going up the old flue and making sure any fumes in the old void don't sink back into your room. A few euros well spent.

(Hilary Jane Dunk) #4


Thanks for this 'surveyor John'...(a lot of Johns on this site)...

As part of the kit for the wood burner, there is a plate which fits the void around the stove pipe just above the chimney piece opening and it is, I believe, standard practice to fit this ?

I've even seen examples on the internet where the void is filled with some sort of insulation material...I'm hoping that is not required by 'le mairie'...another expense and I'm on a really tight budget.

Perhaps the plate comes with some degree of ventilation /holes ?

(John Snell) #5

Sounds like you're on the right track: dismantle back to sound work. It might be unnecessary to mount an extension - depends on the draw of the flue at the stove - worth checking to avoid further expense. But a cap - yes ;- and a fair sized one to keep rain out of the flue, especially during the times when the stove is not in use. A small point, but avoid sealing the (old) flue void thus created; air needs to circulate to wick away moisture.

Surveyors should always look at chimneys - they can say a lot about the property; - not something you get from the diagnostic reports which can create a false sense of confidence when buying. Yes, I'm a surveyor!

(Hilary Jane Dunk) #6

Hi John.

I think it did have a bit of a curve apparent from the roadside when I bought the place in 2007....I don't think it was mentioned at all in the survey that I had done prior to the purchase.....I should probably have negotiated a bit harder and got the price down by getting a price for the building work.....but it seemed so cheap at the time(something that I could never have afforded 'en Angleterre', so I didn't push it.

The building has an attached barn and a couple of small attached outbuildings, (the whole forms an L shape) and could well have been originally part of farm buildings for a small chateau/maison de maitre nearby. The date 1912 appears in masonry on 2 sides of the house...but I think this is when it was probably converted, when other windows and floors were added. The big main room stone fire place is 'grande' and myself, at 5'7" cannot see onto the mantel piece.The exterior wall (behind the fireplace), is flush, there is nothing added on here.

I was thinking that the liner for my wood burner would go up the existing flue, which my sweep ensures me is good..(I'm not sure how this would be fixed at the top of the chimney ?) but in any case it would need to be capped with some sort of cowl to stop rain entering.....It's from the 8th course of bricks as the chimney emerges out of the roof where the bend presumably, if the stack is taken down to that point, then a flue extension, topped with a cowl could do the job, look ok and be alot cheaper than a rebuild.

I need to hear from the man who said he must have built over 2000 chimneys ! Ou est vous ?

I will try and add a couple of photos later, which might help....

(John Snell) #7

Hi Hilary. There's nothing wrong or worrisome about a bit of characterful angle (think Pisa for example), but what you really need to know is whether this is progressive and why it is moving. Bricks are glued together, so if they're on the move it suggests their support is failing;- no wonder your sweep doesn't want to touch it! You mention it has "developed a lean";- when did you last look at it with a critical eye?

And is it the bricks that are "crumbly", or the jointing. A bit of weathering / spalling of bricks is not a cause for concern, within limits _ what is a concern is this: if there's a partial collapse above course No 8; where is it going to fall, and what is your insurance position?

At the risk of being a pedant: modern flues can exit buildings anywhere you want: certainly easier than rebuilding a high-level stack, using conduits fixed to external walls:- don't get hung-up on the need for a new stack. Make it secure, cap it (but allow ventilation into the flue void), and forget it.

No ideas about cost, but suggest you take a closer look at the whys and wherefores as a first step: buildings don't start moving or wobbling without some good reason; it may be nothing other than age; on the other hand it could be movement in the supporting roof / wall structure: from what you say, the stack is not original.....but could have been added to improve the flue draw?