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    Ben Gorman

    Here is Question 11, along with my thoughts about how to answer it. I don’t know whether or not I have the correct answer. I would be really interested in your comments.

    Be aware that the online quiz tends to change the order of the answer options.

    **** QUIZ QUESTION ****

    Ventilation and Airtightness
    Quiz question 11
    When chimney flues through the house are no longer being used what might be sensible ways to both minimise problems and improve health and comfort?
    1. Install a vent in the hearth to provide general house ventilation after sealing up an open fireplace.
    2. Install vents to provide ventilation up the flue to inhibit moisture building up inside the masonry of the chimney stack.
    3. reduce the chimney stack below insulated ceiling levels.
    4. remove chimney and hearth structure altogether to increase room space.

    **** MY THOUGHTS ****

    I’m not sure what the the phrase “reduce the chimney stack below insulated ceiling levels” means. Could anyone explain?

    Presumably 1 would be bad because it could introduce drafts in winter. 2 seems very plausible. 4 would worry me because removing chimney and hearth might cause moisture/mould build in the flue if it wasn’t ventilated.

    Tim Gilbert

    Hi Ben,

    I think that 3 means to remove the top of the chimney so that what remains is within the thermal envelope (and dry). This could work as long as no one lights a fire!

    1 and 2 are the same thing viewed from different angles. Whether the house needs the ventilation will depend of the retrofit but if you are venting the chimney the air has to come from somewhere. Provided the chimney is not on a party wall I would go for 4. When I had work done a while ago I had one chimney removed and another capped and taken up into the loft, so no resultant air movement in the house. Your worries are ill founded because by the end of the job there will be no flue to get damp or ventilate. No chimney, no flue.



    Option 4 of this question got me thinking more than anything else in this homework. Although I don’t have an active project, I’m applying the principles of the course to the terraced house I live in, and I’ve wondered how feasible – if at all! – removing chimney breasts from rooms would be.

    Since the external chimney stack is shared with the neighbouring property, it would be impossible (I assume) to do option 3 – therefore making it pointless to consider option 4, much as it would open up the rooms very nicely!

    I’d be interested to hear any experience of applying these ideas to the chimney in a real terraced house retrofit. Is it a practical consideration, or is it a case of leaving everything intact and making the best of it?

    Tim Gilbert

    Hi Paul,

    I live in a semi, so one side is similar to a terraced house. That is the side where I could not remove the whole chimney, as the neighbour uses theirs.

    The way my builder proceeded was ro remove a slice from the chimney in the loft and support the part above with angle brackets and suitable lintel. My chimney top was capped (x3). He could then remove the lower parts of the chimney and make good. That was 33 years ago and there are no signs of problems in the remaining chimney or loft.

    The space improvement has definitely been worth the expense. Not that I remember how much it was. We would have had expense anyway to make good an already dodgy chimneybreast. I think the price difference was marginal.

    However I do know that some terraced houses have a wide flat chimney where the flues of the different buildings are interdigitated within the line of the party wall (there is probably a correct way to express that) and then you are lumbered. You can only remove your half of the chimney if all your flues, and only yours, are on your side of the party wall. Look at your roof. If you have 2 rows of pots you are probably ok. If you have one row of pots you are not.

    Remember, when making good, that there are flues the other side of the wall and use an airtight parge/plaster, particularly as your work might have compromised the airtightness of the remaining flues. Of course, they may already have been compromised for years but any flue gasses were being drawn up your now nonexistent chimney.


    Tim Gilbert

    PS. The best solution is for you and your neighbour to jointly remove the chimney. Then you really can get rid of the whole thing and remove the risks involved in having a lump of masonry protruding from your roof. Try asking. It won’t hurt.


    Thank you, Tim, that’s really useful insight – and very reassuring that there are potential options! I’ve also done what should have probably been obvious in the first place and started looking around neighbouring streets and properties to see if anybody else has undertaken this type of work. The idea of getting rid of annoying nooks and awkward spaces is very appealing!

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