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Air vents and a lean to

Discussion in 'General DIY' started by Confused In London, 16 Nov 2019.

  1. Confused In London

    Confused In London

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    Hi all,

    My home has an issue that during its many years of life, number of very questionable building choices have prior to my moving there

    The worse of which is the lack of ventilation of the space beneath the ground floor. On top of that, the back of the house has a concrete floor wrap-around lean to which both blocks any air bricks and I think bridges the DPC.

    My thoughts are to cut a several inches wide trough between the concrete and the posterior house wall, unblocking or if necessary installing air bricks to sort out ventilation and then put a removable grate above the trough. The only problem is that one of the rooms, the length of the back wall has a radiator and so the air brick would be basically beneath the radiator and only separated by the floor (wood laminate).

    Is any of this a problem? Does this all make sense or have a missed a trick?

    I have added some incredibly bad drawings

    Thanks
     

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    Last edited: 16 Nov 2019
  2. WonkeyDorey

    WonkeyDorey

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    its a common problem where there ventilation to suspended timber floor blocks off ventilation.
    The normal solution is to add more air bricks around the sides of the house - but this wouldn't be possible in a e.g terrace house.
    New extensions may require laying of a vent and pipe to the subfloor before the concrete is poured. so you are doing something similar but the air is moving over the concretete rather than through a pipe.

    if I understand it. the lean to is unheated area ?

    You do need to adequately ventilate the subfloor to prevent rot which can take many years to manifest as sagging uneven floors.
    The downside of increasing ventilation is that the floor will get colder.
    i have the same issue with my house but as it's detached can add air bricks to the sides of the house.
    I ended up pulling up the floor boards and clearing the debris because someone had dumped a load of bricks and concrete under which no amount of airbrics would improve the airflow through that. I then took that opportunity to insulate with sheep wool as we were keen to have the original floorboards on show. The wool is draped between the joists and prevents draughts as well as insulates.
     
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  4. Confused In London

    Confused In London

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    We have had new joists and clearing out of a lot of damp debris in the subfloor but the builder scarpered before sorting out the ventilation, so we are in this state.

    Exactly, we are terraced.

    The lean to is unheated but will be rebuilt, with better insulated brick walls and conservatory roofing - but that is a couple of years down the line. Though we could probably just whack in a radiator now...

    So as far as you can tell this would be a valid option? Anything you would change or think better?
     
  5. sircerebus666

    sircerebus666

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  7. WonkeyDorey

    WonkeyDorey

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    I'm not an expert but have done a lot of 'research' into my own situation.

    It seems like a valid option. The reason I ask if the outdoor area is heated is that subfloor ventilation usually relies on dry cold air circulating in the winter so you would get a draft in the lean to area which would make it more difficult to keep warm.


    As suggested above the periscope vents are useful when you have no control over the ground level outside but the ease of installing depends if the wall is solid or cavity construction and if you can easily lift the floor boards.

    A solid wall could be a major pain...see
    https://www.diynot.com/diy/threads/installing-airbricks-in-stonewall.211737/

    Your solution sounds more like this picture I found:
    This would be bad idea outdoors as rain could get into the subfloor which clearly not a problem in your case but they must be kept unobstructed by furniture to be effective.

    30030710.jpg



    Here is the sort of system one would use before laying the screed and I doubt that you would want to cut into your existing concrete to retrofit one.
    timloc-1205-in-use-big.jpg

    You can see why people opt to fill their suspended floor with rubble and concrete (with an insulation slab these days).
     
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