Lead flashing or rubber boot for SS chimney exit?

[thesheep]

The twit who fitted our wood burning stove cut the rubber boot too slack, so there is a few mm gap round it and rain comes down the side and into the house.

I've asked the roofer who is working on the house to change it for a new one. He has suggested he could make up a lead flashing kit instead which turns out to be slightly cheaper (the rubber kit is £92 and the lead kit £70).

With the lead they will weld it to the metal of the chimney he says, to seal it. He seems to think the lead is a better bet, but I just wanted to check whether it is better practice to use rubber so the twin-wall can be removed/disassembled if necessary at a future date? Or is this not something to be concerned about?

Thanks

Ben

 

[Agile]

I dont see how he is going to weld to stainless steel!

Lead is generally better as it lasts for 100s of years.

I wonder if he is going to fabricate it himself from lead sheet.

There are ready made sealing units called "lead slates" which have a flexible rubber seal to fit tightly to the flue. The rubber is bonded to the lead.

In most cases its possible to fill smaller gaps up to about 6 mm using the black roofing sealant which comes in tubes and remains flexible to form a good waterproof seal.

Tony

 

[thesheep]

I dont see how he is going to weld to stainless steel!

Looks like you're right! I had misunderstood him. The lead is welded into a shape so it forms a sleeve round the chimney, then he'll use lead sealant to make a seal between that and the SS.

 

[Agile]

I suppose fabricating it himself will be a bit more paid work for him and good fun too.

But it will be difficult ( impossible ? ) to remove and I would always recommend the "lead slate" as the rubber part has sufficient movement to enable the flue to be removed easily.



Tony

 

[thesheep]

Oh. Hmm, I think he has ordered the lead to be made up now... I suppose I could try and get him to cancel it. Hmm.

If I wanted to remove the lead later couldn't we just break the seal and lift the lead over the top of the chimney again, the same way he got it on?

 

[Agile]

The mastic sealant gets very hard and almost impossible to remove after a few years!

Certainly the lead can be cut though.

 

[thesheep]

And here it is...

 

[doitall]

Good job, is the flue the correct distance from any flammable material

 

[thesheep]

Good job, is the flue the correct distance from any flammable material

I certainly hope so. I got the official building regs form thingy when he installed the stove. Is there something in the photo that makes you doubt it?

 

[doitall]

No, just that the flue can get pretty hot, and I would have expected to see a red slate suitable for high temperatures.

 

[thesheep]

No, just that the flue can get pretty hot, and I would have expected to see a red slate suitable for high temperatures.

I'm not sure. The roof is newer than the stove/chimney. I assume the roofer would have put the correct stuff up... could you explain a bit more about where this red slate would be seen? Isn't the slate the bit on the slope of the roof, underneath the lead?

 

[doitall]

Normally with a solid fuel fire one would use a metal slate and storm collar, I would be very concerned the lead will melt as soon as you fire the stove up for any length of time.

The rubber type slates originally fitted have a black rubber or a red rubber for high temperatures.

How long is the flue.

http://www.percydoughty.com/Flue-Products/Twin-Wall/Stainless-Steel/Fitting

 

[thesheep]

OMG is this never ending

The roofer suggested the lead and I had no idea I should be worrying about this.

The flue is twin-walled and has travelled at least 4 metres from the fire by the time it reaches the roof (the stove is on the ground floor and there are a couple of 45 degree bends in there too).

Personally I would be pretty surprised if it got hot enough to melt the lead but I suppose the principle of these things it to always have a wide safety margin.

Looks like lead melts at around 300 celsius? I really can't see it getting that hot on the outside of the roof, through twin-wall insulated flue. Presumably in the winter, when we're likely to be using the fire a lot, the outside air would help cool it too... but I'm definitely not qualified to judge.

 

[thesheep]

Just found this: http://www.stovesonline.co.uk/wood_burning_stoves/Lead-flashings.html which is somewhat reassuring.

I do wonder if I should have a "storm collar" though.

 

[doitall]

If there's a make on the flue asked the Manufacturer.

I've never seen a lead slate on a solid fuel flue yet, that doesn't mean a lot but worth checking.

http://www.selkirkchimney.co.uk/products/twin-wall-chimney.html