Lead tray in chimney

[Johnbelfast]

I have a problem with water ingress in my chimney.  I have a woodturning stove and a stainless steel liner in the flue.  The house is a bungalow built in 1953 but the chimney has been re-built at some point.  The stack is on the edge of the house and does not come through the roof so it is very high -about 8 feet and only 2 bricks wide x 7 bricks long.  There is no lead tray.  A builder has told me i need the stack taken down and rebuilt with a lead tray .  I would like to know if fitting a tray will make the stack weaker and wonder if that was why there isn't one.  Is there any other way I can waterproof the stack without re-building it?

[Temp]

Where are you seeing water on the inside? Chimneys can leak in a lot of different places. 

 

This is how the NHBC say a chimney should be built..

https://www.labcwarranty.co.uk/blog/how-to-ensure-your-chimney-is-constructed-correctly/

[Johnbelfast]

There are damp patches appearing on the wall above the stove and at the coving where the ceiling joins the wall.  In the roof space the woodwork around the base of the chimney is damp and the brickwork is damp.

[Temp]

Might be worth getting a second opinion/quote but could be he's right. Is there any lead flashing between chimney and roof and is that in good condition?

[Johnbelfast]

Yes , the flashing round the chimney looks in good condition.  I've sprayed the brickwork on the stack with Screwfix brick sealant.  Another query I have is about the wisdom of fitting a flue liner and surrounding it with vermiculite.  Surely that could create dampness.  I always understood there should be ventilation in a chimney.

[Declan52]

The vermiculite is used to insulate around the flue so is needed. It's used because it can withstand the high temps that you would get around the flue.

Can you get a ladder out and check the top off the stack to see if water has penetrated  the seal at the top and is working it's way down.

[Johnbelfast]

This morning after another night of heavy rain and wind the water was running down the stack bricks inside the roofspace.  I'm drying it out with a fan heater .  How far can rain drive under lead flashing?  The tiles are flat and the flashing only extends 3-4 inches over the tiles.  I had the flauncing re-done on the top of the chimney because it was cracked.  There is a chimney cowl on the top of the pot.

[Mr Punter]

If the issue is saturated brickwork, you could paint it with Storm Dry.  I think this works OK where there is no cavity tray above conservatories and porches.  Very long lasting apparently.

[Johnbelfast]

I was wondering about Storm dry because I think the issue is saturated brickwork and it would be better to stop the water getting into the stack in the first place rather than stopping it getting further down with a lead tray.  Has anyone else any input on the effectiveness of this treatment?  The chimney pointing is in good condition.

[PeterW]

7 hours ago, Johnbelfast said:

This morning after another night of heavy rain and wind the water was running down the stack bricks inside the roofspace.  I'm drying it out with a fan heater .  How far can rain drive under lead flashing?  The tiles are flat and the flashing only extends 3-4 inches over the tiles.  I had the flauncing re-done on the top of the chimney because it was cracked.  There is a chimney cowl on the top of the pot.

that sounds like a leak and not the brickwork getting wet. Sounds like there are no soakers under the edges of the tiles or they aren’t installed properly. 

[Johnbelfast]

I'll try to get up there and take some pictures of the flashing if the weather is better this week.

[Temp]

I agree with @PeterW that sounds more like a leak.  Lead flashing isn't rocket science but its amazing how badly it gets done.  Generally flashing should be made of separate sheets called soakers that are overlapped and interleaved with plain tiles so that water running down gets diverted to the outside. Sometimes another sheet of lead is put over the top of the lot but its the bit underneath that's  the most important. With wavy pantiles you may only need the one piece top sheet but that's not sufficient with plain tiles.

 

Go carefully in this weather.

Edited February 24, 2020 by Temp

[Jeremy Harris]

We bought a new house that developed a bad leak around the chimney.  Resulted in a fair bit or water damage to a bedroom ceiling.  It turned out that the "builder" had fitted the lead flashing with the overlaps the wrong way around, so water was running underneath the lead at the joints . . .

[Johnbelfast]

I've taken photos and there are no soakers under the tiles , just a strip of lead over the top.

[Johnbelfast]

The first two pictures are of the back of the chimney where it is leaking .  The third picture is on the side which looks better.  The other picture shows how tall the stack is.

[joe90]

IMO it should have soakers as the tiles are offset which means every other tile does not have a ridge to keep the water away from the stack.

[Temp]

To be honest I've seen far worse lead work then that. The tiles are interlocking tiles not plain and..

 

http://www.roofconsult.co.uk/articles/tiling/tips29.htm

 

Flashings
With interlocking tiles, soakers must never be used. Therefore a lead cover flashing will be required. With flat interlocking tiles the minimum side lap distance should be 150mm. However with profiled interlocking tiles side lap cover is not so easy to determine. Many profiled interlocking tiles have a trough that is flush with the side interlock, such that unless the flashing goes over a full roll water creeping in between the flashing and the tiles will run onto the trough of the tile and could run off the edge. The recommendation of the Lead Sheet Association is that the flashing covers a full roll. Depending upon the location of the roll at the side abutment will determine the actual side lap cover distance.

 

So I don't think the top cover is wide enough but not sure if that's the problem.

 

[Johnbelfast]

I have got Tec7 Roof so I could run a bead of that along the edge of the lead top cover.