Advice please: old plaster identification

magicnumber7 · 6 Sep 2020

We are renovating the bathroom in our ground floor flat, in a Victorian terrace converted in 1990. On the back wall (brick) there are layers of old bonding and plaster under the tiles. See picture. There is a patch of old plaster on the right hand side, that sits on top of the brick. It's pinky brown colour. Seems to have dark hairs in it.

Any ideas what type of plaster this is, please?

I need to decide if we are going to strip it right back to the brick, or just layer over it. Thanks!

dontbelieveawordofit · 6 Sep 2020

sounds like old plaster with horse hair added. common practice until the late 40s -50s.
or it could be jointing material , the old fashioned version of scrim tape.
most important thing is that all the walls are dry.

ted456 · 6 Sep 2020

OP,

1900 plaster was a lime plaster that was often mixed with horse hair - your walls show various kinds of plaster patches plus dabs and lines of adhesive.
At the inside corner there appears to be a gap?
Your best bet might be to remove all the plaster back to brick, & start with a fresh surface for going forward with your project.

Hessian Scrim was the go-to "tape" before the mid 20thC - Hessian Scrim is still available, and very useful indeed in the hands of experienced, time served tradespeople. ie. People who know what they are doing.
But, from the pic you show, there would have been no need for Hessian Scrim in that position.

magicnumber7 · 6 Sep 2020

Thank you, both.

I am tempted just to take it back to the brick. I presume the other option would be skim / board over it all to create fat surface for fresh tiles...?

ted456 · 6 Sep 2020

If you take it back to brick you can render the walls with lime render and tile directly on to the surface.
Or, you can board all wet wall areas with backer board, and use plasterboard for dry areas.

dontbelieveawordofit · 6 Sep 2020

the advice regarding lime render in your bathroom will end you up in a load of bother unless you know exactly what you are doing.
lime render needs time in the correct conditions to cure perfectly or you will end up with a feeble substrate not suitable and unable to take the weight of modern ceramics.
hack the old plaster off back to brick work and dryline the walls with suitable backing materials.
for accurate professional advice on drylining or cement/lime rendering techniques i’d suggest you post in the plasterers forum.
there’s some seriously worrying advice regarding antique ,outdated methods of remedial/renovation techniques being advised here lately which are best left to professionals. in particular lime rendering which seems to be bandied about as if it’s a stroll in the park.
good luck

dontbelieveawordofit · 6 Sep 2020

magicnumber7 said:
Thank you, both.

I am tempted just to take it back to the brick. I presume the other option would be skim / board over it all to create fat surface for fresh tiles...?

yes. dry line with appropriate materials . nice and flat and plumb for a modern finish

dontbelieveawordofit · 6 Sep 2020

ted456 said:
If you take it back to brick you can render the walls with lime render and tile directly on to the surface.
Or, you can board all wet wall areas with backer board, and use plasterboard for dry areas.

what makes you think that DIYERS coming here looking for advice have the wherewithal to correctly mix, correctly apply , correctly monitor the curing process , correctly observe health and safety procedures with potentially dangerous materials. your advice is nothing short of ignorant and dangerous.
you need to be banned before somebody gets hurt or their health is affected by your foolhardy rants and opinions

magicnumber7 · 25 Sep 2020

bennymultifinish said:
yes. dry line with appropriate materials . nice and flat and plumb for a modern finish

Thanks. A recent photo attached. It's the brick wall in the background. Once cleared of all surface plaster, the next step would be something like dot and dab plasterboard, then skim?

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Advice please: old plaster identification

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