Chimneys & Fireplaces Question

How necessary is it to let an unused chimney breathe??

Our plan is to remove an existing 4 pot chimney down to the bedroom roof joists. Only one chimney is still in use for a multifuel burner, one was sealed many years ago while the other two have vents into the bedrooms where fireplaces used to exist. A contracter has advised us to have the two unused bedroom chimneys piped together via an inverted "Y" type connection and then piped out through the roof. Is this necessary or can they been sealed off at joist height?
If so do we cap them completely or use vents to let them breath?

5 Answers

Best Answer

Bottom line. if you disuse a flue or chimney you must vent,to let it breath so condensation does not build up and freeze causing expansion and a falling down stack!!


Answered 16th Feb 2012

kelly plumbing Heating & gas

Member since 4 Jan 2012

If you are only talking a few feet of redundant flue then you'll probably be ok with fully capping after reducing the height, with a single vent left in the blocked-up fireplace. If the remaining length of chimney is greater than a single storey it's better to provide through venting by either doing as your contractor has suggested or if the chimney is to be terminated within a vented loft space you could potentially vent the top into the loft.

Answered 18th Nov 2011

Trigonometry Construction Ltd

Member since 3 Jun 2010

If they are redundant just cap them, vent top and bottom.

Answered 18th Nov 2011


Member since 29 Oct 2008

You have to vent top and bottom as the lads above have stated.


Answered 3rd May 2013

DAW contracts

Member since 11 Apr 2012

If they're dropped under the roof, make sure the loft is well ventilated, condensation will happen and the sooty deposits inside the flues love any form of damp

Answered 22nd Jan 2014

Craig walton

Member since 10 Oct 2013

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