Damp from Chimneys

[kreyszig]

Hello all

We've not long moved into a Victorian semi, a lovely place indeed.
We had a building survey done prior to purchase, and the surveyor recommended rebuilding the chimneys in order to insert a lead sheet, to prevent damp. There are obvious signs of damp in all three rooms on the top floor which the chimneys pass through, some more than others.

That was the recommendation, but as a bare minimum he reckoned we need to repoint the top of the chimneys.
There are three chimneys, two on the eaves and one at the back thats a bit more difficult to get at. But everyone that's looked has said scaffolding access is good.

Obviously rebuilding is going to be/would be pretty expensive. The more I look at them I think they look ok apart from the very top, and that water ingress is likely from cracked flaunchings, so rebuilding the top part could be a reasonable move.

I'd be interested in any advice you can give about what I can look for to indicate whether I do or don't need to rebuild.

Currently one chimney has an open fire which we would like to put a woodburner in, the rear chimney has an open flue boiler running up it and there is a gas fire in another chimney - so we could I hope keep a bit of heat in them over the winter, and that this might help a bit.

Some pictures; they are not very good I'm afraid as they've come from the first viewing. But you can see the general condition I hope:

rear chimney

rear side chimney

front side chimney, algae

 

[MatthewC]

Hi, that's a nice looking house and the chimneys do not seem to be in awful condition, apart from lacking two pots by the look of it. The condition looks a lot better than mine did, and at least if they do need doing, you should only be replacing the top course or two with the flaunching - we had to replace nine courses down on one!

I've got a wood burner in one with a stainless steel flue (expensive!), and an open fire under another. Both these have fancy ugly things on which stop birds and most of the rain. I've also got two more unused which have clay sailor caps on for cover with ventilation. We were also plastering throughout so any leakage was covered by a good layer of lime plaster and have had no problems.

You must know a good bit already to know what "flaunching" is! I'm not sure what the lead sheet would do apart from flashing - if he means lining the chimney, that's not a solution I've heard of (but I'm sure someone here will know).

Matthew

 

[malcolm]

Were there any fireplaces in the first floor that have now been blocked off? The advice I've had is to put an vent in where the fireplace was and to pop a chimney pot with a cover on over the disused chimney. That's the venting approach to getting rid of damp. Might well be other approaches that waste heat a little less.

 

[stuart45]

I'm not sure what the lead sheet would do apart from flashing - if he means lining the chimney, that's not a solution I've heard of (but I'm sure someone here will know).

Matthew

It's probably a lead tray. It's always put in new build chimneys to stop moisture getting down the stack. Just lead has a good video on line on how to install one.

 

[kreyszig]

Thanks all for the replies!
Laad tray - that's the one. I haven't seen anything about retrofitting one without rebuilding the entire stack. It's a horizontal sheet that goes through the stack with a hole for the flue - and is installed at the roofline.
All the fireplaces on the first floor are still open or vented.

It's reassuring to hear someone is thinking along the same lines as me. As for knowing about flaunching - I've been reading what I can, but it's all new to me!

Anyway, more pics to come!

 

[plasticpigeon]

I think maybe just start with sorting the flaunching out and putting a vented cap on the pots, My chimneys don't give any hassle and they don't have lead trays and 2 of them aren't even in good condition.

 

[Zebra]

There was a discussion on a similar topic here.
http://periodproperty.co.uk/forum/viewtopic.php?f=1&t=13645

 

[stuart45]

I think maybe just start with sorting the flaunching out and putting a vented cap on the pots, My chimneys don't give any hassle and they don't have lead trays and 2 of them aren't even in good condition.

Chimneys years ago didn't have trays and probably didn't need them. Back then the fires were daily more and this helped keep the stacks dry. In modern times, the fires may only be used once a week or even less, so damp has become more of a problem.

 

[Svenedin]

I have some recent personal experience of damp from chimneys. We had a damp chimney breast and I thought it might be the flaunching. We went up to investigate and found that the flaunching was in good condition. We concluded that it was probably rain coming straight down the chimney pot so we put a MAD cowl (metal anti-downdraft cowl) on the offending pot (we worked out which one it was by using a smoke pellet in the fireplace below, it wasn't the one we thought it was). Since putting the cowl on the damp problem has completely resolved. Strangely, this rain down the chimney problem doesn't seem to affect other chimneys in the house. Of course the damp could be caused by many other things: bad flashing, cracks in the lead of a valley, broken slates, or mortar missing between bricks in the stack but sometimes it isn't nearly as complicated as that. My chimney has an open fire below but of course this is only used in winter. We could have used a different type of cowl if the chimney was not being used.

 

[DJH]

Chimneys do need dampcourses in them whether they are of lead, which is the correct material to use, or a token plastic membrane. I suspect they were never fitted, although it has always been recognised as a necessity, through cost cutting, ignorance or 'that'll be all right we'll be long gone by then' attitude' which has prevailed since the year dot in the building industry which is why we are all having our various problems today such as lack of dpc's for example...

Doug

 

[kreyszig]

Thanks again all for the input. I took some more pictures on the weekend but haven't got any of the side chimneys from across the street, and of course it's raining now.
I did realise though that I've posted a picture of the neighbours chimney as if it were our rear stack! What a numpty.

Ours has 4 pots and an additional metal pot thing for the boiler. I'm a bit confused by that..perhaps they've kept a pot for decorative purposes...there are only two fireplaces on the first floor, the boiler on the kitchen side and a rayburn on the dining room side (another mystery to me) of the ground floor. No basement.
Anyway I'll put what I've got up this evening. One of the pictures shows the state of the vegetation on the rear chimney.

edit:
I put some pictures up here. Your thoughts on whether these look like they need rebuilding most welcome!

 

[kreyszig]

...I've just come from meeting another builder who insisted that rebuilding the entire chimneys and putting in a lead tray is the only way to stop moisture getting in.
His argument was that there's only 4 inches of brick between the outside of the chimney and the inside..? To be honest it felt like a marketing spiel from the get-go; he hardly looked at them.
Is this the voice of experience, or the voice of someone trying to maximise ££ I wonder.. also, if you missed it there are more pictures of the chimneys in my previous post in a link at the end.
I might have bigger fish to fry though; I went up in the loft to see if there was much damp apparent (it's raining pretty heavily here) and found a large split in one of the roof beams, in an area I know the surveyor didn't look at, because there weren't boards down. le sigh

oh - I noticed a drip in one of the first floor fireplaces. So definitely some water coming down the inside. The bits of the chimney I could see upstairs seemed dry (I couldn't physically get to one of them due to lack of boards)

 

[Zebra]

A complete rebuild might be the only way to be absolutely 100% definately certain once and for all that no damp comes down the chimney. However, if you sorted the lesser problems first, the flaunching and the pot, perhaps a bit of pointing, you may save yourself a heap of money.
Isn't it often the way, that you're not sure what will solve the problem, and all you can do is try something, see if it solves the problem, and if not try something else. Understand that you don't want to pay for scaffolding twice over, but you may just have to take a chance on it.
Pot and flaunching should solve the drip coming down the inside of the chimney. I'd get in the loft again and have a proper look at the stacks, and see how wet they are, and try to figure out whether that's the cause of the damp in the rooms below, and sort the drip coming down the inside of the chimney, before accepting a quote for a full chimney rebuild if it were me....

 

[plasticpigeon]

My not hugely experienced opinion is that your chimneys are very nice, quite fancy and the bricks look very good quality. I imagine the top few bricks may be loose and especially where there is vegetation so the top few courses probably need rebuilding and new flaunching put on. I can't see why the whole thing needs to be rebuilt.

My experience with chimneys is that I had a very distorted chimney with 3 pots at the back of my house. The 3 pots were originally for the copper, range and upstairs fireplace. I had it rebuilt as was leaning considerably and it looked dangerous not because of damp!!! I also had some cowls put on that looked like ridge tiles. However the rather poor builders that did the chimney didn't know to mortar these on so all the water that hit the top of the cowl ran down the sides and into the chimney so there was quite a lot of water dripping down the stack. This didn't manifest itself as damp on any walls though. I put caps on top that overhang the edges of the pot so no water comes down and all seems dry now without lead trays. I would say that builder is touting for more work than necessary so avoid him. I think t is quite likely that the plan of action may be determined by what is found when someone actually gets up there to have a look. Just my 2 pence worth.

 

[kreyszig]

Thanks for that people, I wonder if I'm going nuts sometimes the number of builders that are pushing for a rebuild as if it were the only choice. Comments like Zebras read to me as complete common sense. I'll keep going until I find someone that's happy to just do the tops!

Thanks again - I appreciate the dose of sanity! (Off to figure out what to do about that beam now)

 

[DJH]

I have some sympathy with the builders in this case as the only solution to the problem of damp in chimneys is to take them down and rebuild with trays taking the opportunity to insulate the liners at the same time. The costs involved with scaffold and access is the same whether the chimneys are patched up or repaired and should the patching up fail within a few years then up goes the scaffold again with the resultant comments... that chimney was done by so and so only last year etc etc and the builder who did the original work gets a bad name.

I had similar occasions years ago when I was asked to patch up splits in lead roofs by using flashband or similar sticky black stuff and I'm afraid I always refused and welded lead patches over them instead as I knew that one day the roof would require major works and, in the lead world, it would soon have spread that I was doing substandard work. It's human nature after all to criticise!!

It's a hard choice to make but, as always, it's down to cost but if you can get some bloke with a bucket and a trowel to shin up a ladder on the roof and throw some muck at them then give it a go... :shock:

If you do take off the top couple of courses then fit a dpc under them which will help discourage damp from percolating down into the structure below although that will of course always get wet in adverse conditions.

As always, tough decisions...

Doug

 

[Zebra]

Very interesting point of view Doug, I hadn't considered it from the builders point of view but can see exactly what you mean.

There's a couple of things I've had done to my house - using unusal products for example - where I've made it absolutely clear to the tradespeople concerned that I need their skills but take full responsiblity for the results!