dropping chimney

7 Aug 2010
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United Kingdom

I am going to be dropping the chimney below the roofline on my bungalow and would like to know the exact way to re-fit the flue.
I've got a bit of an idea, but want to know the exact way.

I know the chimney has to be dropped low enough for it to be inspected around the top, but what is the minimum distance below the roof.

The flexible liner is 5" and fits through the 5" lead slate, but does not fit inside the rigid liner (which is a twin wall liner) that I need to drop into the top of the chimney.

Can some type of reducing liner be sealed to the existing liner, so that I can then fit it through the rigid one.

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Chimney dropped to not less than 1000mm from anything combustible.

Flexible liner terminates at top of remaining flue then fit a clamping plate to liner to hold it level with top of vent.

Used to be we would connect a gas hood to the clamping plate which in turn you would lock your length of twin wall into, this method was specified when we were dropping chimneyheads for the local authority whilst doing re-roofs.
When appropriate the twin wall was connected to an RTA (ridge tile adaptor) and vented through a gas ridge.

Last one we done was around 4yrs ago so regs may be different now.

Clamping plate is sealed to chimney stub with 4-1 sand mortar mix.

Gas flue venting was always tested and checked by gas safe bod.


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