Hello

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!

Phil

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.

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.

Phil

other side

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.

bigger gap than i thought. looks easy to put an extra lintel or two in the middle.

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.