Lime plaster and gypsum

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ktf-2021
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Joined: Sat 3rd Apr, 2021 6:23 pm

Lime plaster and gypsum

Post by ktf-2021 » Tue 6th Apr, 2021 6:23 pm

Hi all

Recently moved to a terrace house built in 1901. Got all the woodchip off (and the 60s wallpaper underneath) and it's lime plaster. Decided to prioritise living room so we have somewhere nice to hang out in the evenings. Several plasterers have been to quote but we've done a bit of research and are now panicking that we shouldn't be getting new plaster/gypsum skimmed over lime. However lime specialists are said to be 2-3 times the price (5 bed that will all need doing :shock: ) and hard to find. We're in East Kent. It's a pretty deprived area so I'd be very surprised if everyone was splashing out on authentic lime...

Has anyone been in a similar situation? What did you do? Does 2 or 3 times the price sound right? I don't want to cut corners and cause problems further down the line but I also don't want to spend all of our budget on just the skimming when we have no sofa/bed etc :(

Thanks :)

plasticpigeon
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Location: Birmingham

Re: Lime plaster and gypsum

Post by plasticpigeon » Thu 8th Apr, 2021 10:31 am

I live in a terraced house of pretty much the same age as yours and had similar questions. Your house will almost certainly have a slate damp proof course so I don't think lime plaster is essential in such cases. The original lime plaster in my house was in a terrible state with huge chunks of it collecting in piles at the bottom of the wallpaper that was duct taped to the skirting boards in many areas. Certainly I have had my house replastered with gypsum and don't have damp problems. I don't like boarding so I got hardwall and skim. The one exception was in the kitchen where the dividing pantry wall has no damp proof course and sits on earth. It was covered in hardboard and was damp underneath the board. I laid a limecrete floor which I am certain helped a lot. I also lime plastered that room. It is damp free but I think it if was doing it again I wouldn't be so fussed and would probably do gypsum apart form on the pantry wall with no dpc. More important in my opinion is to make sure that the plaster does not bridge the dpc and that the air bricks and under floor space are clear so that there is decent air flow under the floor. In my house a mix of high ground levels and blocked air bricks caused damp damage to the suspended floor. I know this is not a rigorous conservation approach but I thin, it is appropriate for the style and age of building.

MatthewC
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Re: Lime plaster and gypsum

Post by MatthewC » Thu 8th Apr, 2021 10:51 am

Hi there, welcome to the forum. Lots of advice here, and no question is too silly to be asked, but do search the forum for previous advice.

You don't actually say WHY you want to replaster/skim over the lime (NB well done for getting the woodchip off!). Also please say if the walls are internal or external and what the structure of the wall is. Any wall that has be subject to dampness (e.g. by a broken or blocked downpipe/gutter) will need to have that issue fixed and then you must let the wall dry out before plastering. If you plaster on a wet wall, lime will not set properly, and gypsum will always be cold as you will have sealed the damp in.

If the plaster is completely popped (sounds hollow when tapped, meaning large areas have come adrift from the lath/brick/stone behind), then you will need to have it all off (VERY messy) and replaster completely. If it's popped in just a few small areas, then leave well alone! OTOH, if you want to skim the surface because it has been slightly scratched by the scraper in doing the wallpaper removal, then I personally would advise using any normal filler, applied with care where required - a few small filled scrapes will be OK in my view - and paper or paint over. If the surface is completely scratched then obviously that's a different job, so I guess that's where you are?

Lime plastering is indeed more expensive due to the setting time of the plaster when applying several thick-ish layers, and the rework that is done a few hours after it has been applied (so they do less each day than with gypsum). If you want simply to skim a wall with a single coat of fine plaster then that problem does not apply (if I recall correctly) as the final coat does not get re-worked as the earlier ones do. You might need to apply some special paint before plastering to improve adhesion (I used stuff called DG27 but others are available).

Finally, your choice of adhesive, paper and/or paint will be critical if the wall is to breathe. My brother once applied vinyl wallpaper to a damp lime wall, and it literally fell off (and the room was always very cold).

Hope this helps; I'm the wrong side of London to help with contractors.

Matthew
See my blog at http://houseintheenchantedforest.blogspot.com/

Feltwell
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Re: Lime plaster and gypsum

Post by Feltwell » Fri 9th Apr, 2021 12:04 am

Or - for another option -

If it is just the case that the plaster is well adhered but not smooth enough for what you want, hanging non woven heavy duty lining paper before you paint can work wonders.

This stuff - used with ready mixed adhesive - is much more expensive than cheaper lining papers but does a far, far better job.

https://www.decoratingdirect.co.uk/viewprod/m/MAVNWLPV/

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