Plaster advice for an old house

[Merrow]

We're needing a room replastered and I'm not sure what sort of plastering we need! The house was built in 1910, and the issues with the plaster have been caused, we've been told, by the previous owners using gypsum over lime plaster. I suspect we'll be going back to brick for the whole room, but it is one wall that has failed pretty completely. Until a conversation yesterday I didn't realise there were different plastering options - I assumed if it was down to the brick work it wouldn't matter. Now having looked into it a bit I'm mainly just confused.

Is it always best to use lime plaster in an old house if that was that was there originally? There's one external wall (and the patio doors take up a lot of space on that wall). There's pretty considerable cracks everywhere so we assume some movement.

Any advice appreciated - we've a recommended plasterer coming to quote on Wednesday, but I've no idea if he does lime plastering and if he doesn't I'm less inclined to trust his opinion on whether or not it's necessary.

I'm in the building trade.

Gypsum over lime will crack, because gypsum dries very hard, whereas lime has some flexibility.

Lime was used in the past in part because it was the available product, but in part because it forgives slight structural movement, which is common in older properties that often don't have the foundation depth and dimensional stability of newer builds.

Technically, if you strip to brick you could go over with a bonding render then a topcoat of gypsum, but you risk nasty cracks if there is even slight movement.

You could also batten and board or dot and dab with a flexible adhesive, both methods are pisspoor and to be avoided.

The best thing to do would be to find a plasterer who can do lime and have it done in that.

Another reason for lime is it allows more moisture transfer, so allows the wall to breathe, older houses often don't have cavities or modern DPCs and gypsum coatings can cause damp spots that refuse to ever truly dry.

My advice with any older property is to use the construction methods used when it was built where at all possible to avoid issues.

Hi OP

older properties need to breath so anything you put on either side needs to be vapour permeable. The issues you have will be because modern materials have been used. Normally causing damp and so on.

so strip back to brick and allow it all to dry out for a year then re group on if you want to like plaster at that point.

also check outside, do you have leaky gutter, raised ground levels, has the outside been rendered/pointed in cement? All these would contribute to a “failing wall”.

you really do need to find trades that understand heritage properties and techniques.

I also suggest you join the Facebook group Your old House UK - Repair and Conservation, there are many people like you on there alongside conservation officers and expert trades.

I'm not sure about cracking as we've returned back to lime for breathability. Possibly the same applies. I am told lime also responds better to movement.

Go back to brick and use lime on the internal walls if you are advised that's the issue. Breathable, material that would have been used and as long as you don't use any modern bonding materials you will be fine.

Talk to your local lime plaster merchants as its best to get a local mix. They'll happily advise.

My husband did a £150 course, and we then took instructions from a merchant and did it ourselves as funds are tight. Was our first attempt perfect - no in places. But our next room was miles better and also lime if forgiving, it is still a bit squishy in the days after. Wear gloves etc. Mask when mixing.

Whatever you do, do NOT ruin your grest job with modern paint.

Use breathable. INGILBY in Sudbury is always recommended. Dirt cheap, family run firm, free advice. And no i haven't got shares!! Their lime wash paint can be colour mixed and is so good to use.

You can't paint straight away, but it's ok as the wall turns cream with lime so it looks ok.

Also if anything has been wet our surveyor said expect a good 18months plus to fully dry. The lime will keep drawing out the moisture (in a good way).

Really you need roaring log burners or fire on over the years with airing and vents.

Old houses just need to breathe and move. We're now going to do lime on our extension as it worked out cheaper and we enjoyed it.

Thank you very much everyone, sounds like there's consensus on lime! There

Check out the SPAB website and SPAB books on renovations

Yes to lime plaster and breathable paints aswell
Don’t seal the plaster with any glue based paints. It will lock in moisture
The same goes for wallpapering over