Sealing external log burner flue

26 Jul 2014
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United Kingdom

We have a log burner with an exposed metal flue. Rain water has started to run down the flue inside the house and pool on top of the burner.

On the roof I can see a metal skirt around the flue that has been bolted tight around the flue before it enters the roof through lead flashing.

Anyone know what sealant I should use to try and seal any gaps? Needs to be able to cope with the heat and cold.

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Sounds as though there is no chimney pot on top of the flue; is there an anti downdraught cowl. Post a picture of the tope please.
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If the flue is correctly jointed from roof to top of stove then most likely any water on top of the stove is running down the outside of the pipe.
There can be more than one possible entry points, the first you have identified which is failure of the storm collar to external surface seal.
This collar should overlap,enclosing the top edge of the up stand of the lead flashing so should be well sealed. I have found the most reliable way to do this is to squirt a good ring of the sealer linked to above slightly above the lead, then slide the loosly clamped storm collar down till it starts squeeze up through the joint.
Tighten the clamp and add a bit more sealer and finish with wet finger.
Another point of entry can be the weld between the flat and upstand of the lead flashing which can fail due to stress from excess movement of the flue in windy conditions, possibly due to poor rafter/roof supports.

To my mind but not having seen the installation, if it were entering inside the flue through lack of of cowl it should end up inside the stove or in a soot box?

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