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    We are planning a refurbishment of an 1850s sandstone building in North Yorkshire. While doing some opening up to see what is there we removed some plasterboard from above a window reveal. The inner and outer leaf are well supported on 170mm deep concrete lintels but the rubble core inside has a triangular defect running about 450mm up from the reveal level. roughly the same shape and proportions as a piece of toblerone.

    The window is not original but was put in sometime between 1940 and 1990 along with 2 others we have not opened up yet.

    The question is how to deal with this. I would anticipate lime mortar and sandstone rubble gradually built up, with some form of either temporary or permanent supports to hold it in place, and how should it be finished to prevent further collapse. The final finish is probably going to be insulating lime plaster.

    Any thoughts or experiences gratefully received - already worked out will want seriously good eye protection!

    • CommentAuthortony
    • CommentTimeDec 17th 2019
    Foam in polystyrene sheets with non expanding foam
    • CommentAuthorvord
    • CommentTimeDec 17th 2019
    Foam might not be the best for filling a hole in an old wall. Breathable structures have water vapour going back and forth and interrupting the flow tends to result in actual water which can get annoying. This sounds like a building question rather than an an insulation question so might be worth another ask on the period property forum.

    Photos would be helpful. I've found it possible to insulate an old house, and have learned a lot from mistakes made in the past that caused the walls to go green with mould.
    • CommentAuthorjfb
    • CommentTimeDec 17th 2019
    Hard to picture exactly what the gap is (photo?). Structurally it doesn't sound as an issue. Filling with lime mortar and rubble should be fine. Or shape some stone/block to fit in the gap and then muck it in. If I am right and you are looking up at the gap as you say eye protection might be needed. Throwing the mortar up with some force from a trowel might be the best way. Then bit more muck ontoop of the rubble you push up into the gap. Make sure the mix is not too wet.

    Have you considered wood fibre board as insulation? If you have a flat surface already to work on (that is existing lime plaster is in ok state and straight enough to board straight on top?) It could well be worth it. Insulating render is much more expensive for an equivalent level of insulation with wood fibre board. But it needs render on top as well so it might depend how much you are doiing yourself.
    Thanks for responses so far. - pictures attached as requested

    We are wanting to have a breathable solution because of the old structure of the house.
    We have considered wood board and would prefer to use it however:
    We have a problem with space on the front wall. The doorways into the 2 front rooms are set directly on the inside of the front wall. We will only be able to manage40mm of insulation (solid central wall and staircase mean we cant move them). While the outside is dressed stone the inside leaf is uneven rubble. By the time it is smoothed off, or battened out we will have little space for wood board. We have to go back to the wall as there are between 1 and 3 layers of gypsum plaster over the original lime. The insulating plaster will parge, smooth seal and insulate from the wall inwards. If anyone can think of a way round that we would be delighted.
    Also our interstital calcs suggest that there would be condensation at the wall/insulation interface, and also our walls tend to be moist due to high groundwater levels (built on the springline and we have a spring at the back of the house) and driven moisture (500ft up within 1 mile of the North sea, nothing between us and Denmark). Would that levl of moisture be a problem for wood boards?

    The photos show the window and the hole, plus a couple of the inside of the hole. Hope they help.

    and another
    other side
    and now with picture!
    • CommentAuthorrevor
    • CommentTimeDec 18th 2019
    I think originally the rubble infill would have been supported with wooden lintels a well as the outer an inner walls. When I did our refurb and put new windows in, in a similar situation you have here, I had to put in several (4 or 5) 6x4 concrete lintels to replace the timbers that were there as recommended by building control to support the infill. There will always be a danger of rubble falling although judging by the photos they look pretty big stones. I left a small gap between the lintels them with foam in the gap to help reduce cold bridging and then insulated the "concrete lintel ceiling" in the reveal with insulated plaster board. The wall above can then still breathe. I think you should put lintels in. Is LABC involved ? I guess they would insist on it.
    • CommentAuthorgyrogear
    • CommentTimeDec 19th 2019
    Posted By: Phil & ColetteThe inner and outer leaf are well supported on 170mm deep concrete lintels
    Posted By: revorI think you should put lintels in.


    (especially if there is any fracking expected back in your part of the world...)

    • CommentAuthorjfb
    • CommentTimeDec 19th 2019
    bigger gap than i thought. looks easy to put an extra lintel or two in the middle.
    Thanks again

    LABC will be involved when everything finalised.

    Will be able to get one lintel in and build up from it into the void, the second one wont be possible (unless they make telescopic concrete) due to the big ones on the inner and outer leaf. Insulated gap will be good idea. Should really have been done when the window was put in I guess back in the 50s or 60s. There was a 1997 refurb done when the plasterboard went up, presumably the architect, builder LABC ignored/avoided the hole. All before we moved in.

    When we took the plasterboard down there was some debris and dust but certainly not tthe amount that would have come from the void.

    This is a relatively new window, the original windows do indeed have a series of wooden lintel acros the whole reveal.

    Not too worried about fracking round here as we are in the National Park, and more to the point the new Potash Mine would object (and have bought a lot of the mineral rights). Also the fault line at the top of the garden should keep them away!

    • CommentAuthortychwarel
    • CommentTimeDec 21st 2019
    Why bother doing anything with it, as you say it hasn't moved since the plasterboard was last put up.therefore the stone work above is acting as an arch.
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