Plasterers think I'm mental...

[HookHouseResto]

Hi all,

First post and maybe a bit of a tired subject but: LIME PLASTER!

We're redecorating a bedroom in our 1902 solid brick walled home and the plaster on the external walls is sounding very hollow (I think following water damage from a chimney in poor condition) so we have engaged with a few plasterers. We've suggested that we'll do the donkey work and take the walls back to brick for them and then we'd like a lime plaster base coat and finish coat on there and that we're doing so because we want to maintain breatheability (particularly as I'm looking at EWI on the biggest wall at some point). A couple have come round and were then never heard from again but we did get a pair of brothers come round who seemed to take on what we were after and gave a preliminary quote.

However later calls have been essentially the one brother trying to convince me that they can do the lime base coat but then we should just skim the whole room in multi-finish as we're getting the ceiling done with that anyway. They are literally lime plastering specialists and I'm still a bit wet behind the ears on this old house stuff but... multi-finish won't breathe will it? What's the point in me having them put lime plaster on if they're just gonna cover it with that! He doesn't seem to get what I'm trying to achieve.

Its frustrating as we are on a bit of a schedule due to our second baby due date's rapid approach but not many plasterers seem to want to get involved in lime around here.


Having said all that I'm now thinking of doing internal wall insulation and I reckon these plasterers are going to think I've properly lost it if I start talking about vapour open wood fibre board!

 

[Lacan07]

Hi all,

First post and maybe a bit of a tired subject but: LIME PLASTER!

We're redecorating a bedroom in our 1902 solid brick walled home and the plaster on the external walls is sounding very hollow (I think following water damage from a chimney in poor condition) so we have engaged with a few plasterers. We've suggested that we'll do the donkey work and take the walls back to brick for them and then we'd like a lime plaster base coat and finish coat on there and that we're doing so because we want to maintain breatheability (particularly as I'm looking at EWI on the biggest wall at some point). A couple have come round and were then never heard from again but we did get a pair of brothers come round who seemed to take on what we were after and gave a preliminary quote.

However later calls have been essentially the one brother trying to convince me that they can do the lime base coat but then we should just skim the whole room in multi-finish as we're getting the ceiling done with that anyway. They are literally lime plastering specialists and I'm still a bit wet behind the ears on this old house stuff but... multi-finish won't breathe will it? What's the point in me having them put lime plaster on if they're just gonna cover it with that! He doesn't seem to get what I'm trying to achieve.

Its frustrating as we are on a bit of a schedule due to our second baby due date's rapid approach but not many plasterers seem to want to get involved in lime around here.


Having said all that I'm now thinking of doing internal wall insulation and I reckon these plasterers are going to think I've properly lost it if I start talking about vapour open wood fibre board!

You're correct, multi finish is not breathable. I doubt these brothers are lime specialists if they want to multi finish skim over a lime base.

Are you sure you haven't misconstrued what's been said, maybe they're saying multi finish the ceiling and internal walls whilst the external wall remains lime. This is usually quite common practice.

EWI is considered more effective than IWI but only if you have a fairly empty wall free of outlets, soil pipes, etc. Neither will be cheap unfortunately unless you're willing to get involved.

 

[Kearn]

I wouldn’t waste the effort and money on the board for insulation, as long as the external brickwork is free from rubbish and able to maintain staying dry, then just go thick internally straight onto brick with hemp lime as a base and even scratch coat, before finishing. You can build a very thick single coat, more so than with haired lime, generating good insulating properties with no air gaps.

However, if you have existing lime on the wall, why remove at all? Hollow plaster can be saved and it’s likely just in a couple of discrete locations where it has lost its key. Stainless screws and a bit of jiggery pokery can pull the detached areas back onto the brick carefully without over stressing the lime, and you can then just deal with the small fixing areas. And for such small touch ups, polyfilla is absolutely fine and won’t compromise the performance of the entire wall.

There’s a general rule of not going looking for work, and stripping entire walls then replastering is a messy, slow and expensive job than most would avoid if possible.

Competent lime plasterers are few and far between, and therefore won’t be available for a long time, if they’re even interested. Once they are, depending on your location you’re looking at £130-180 a square metre. That’s assuming you’ve done the removal already. It’s then 3 visits to apply plaster, plus any intermediate maintenance and checking. And another 6+ weeks once complete before you can decorate.

And yes you’re right, the chuckle bros shouldn’t be trusted if that is their advice - I imagine the base coat won’t be actually lime either, just a sand cement mix with a bit of powdered lime thrown in…

 

[mardinor]

Leave well alone. Nothing wrong with hollow sounding plaster on walls - just don't knock on them! Ceilings above beds may be another matter, but even then the SS washer trick works well.

 

[larry]

I've been in a similar situation but paying somebody to do the work really isn't an option..I've had a fair bit of luck with Breathaplasta and the "magic sponge" trick. Leaves a textured finish but looks good enough for me. Then breathable paint on top. That's been over wood fibre boards.

The worst part is stripping back the years of paint and paper on top of the old lime plaster. Absolute nightmare. Plastering over the top was a relative doddle!

Ps I'm not convinced gypsum is unbreathable but PVA commonly used to control suction certainly isn't and in any case an equally important property is flexibility (how are your big concrete foundations looking?), which multifinish certainly is not.

Recommended Tikkurilla paints, reasonable price and they publish SD values so you can see how vapour permeable they are.

 

[paulc]

Ps I'm not convinced gypsum is unbreathable

I'm kinda leaning that direction myself. With the pink stuff, there is a noticeable change in colour when it gets wet, and then it will slowly turn pink again as it dries. However, gypsum is water soluble, so if the plaster is exposed to prolonged damp, it will turn to a mush. Lime plaster is much better at handling damp conditions, so wins out on walls that lack a DPC or are subject to periods of penetrating damp.

 

[malcolm]

The gypsum on my walls doesn't dry quickly. It just sits there being damp and clammy. The thin skim takes weeks to dry. Replace it with lime and the lime dries fine.

While gypsum is not completely impermeable it is not breathable enough for my needs

 

[Stevers]

Gypsum plaster is breathable, but hygroscopic according to my (and Bing's) understanding, so penetrating damp and condensation will be uneasy bedfellows with gypsum plasters.

 

[malcolm]

Gypsum plaster is breathable, but hygroscopic according to my (and Bing's) understanding, so penetrating damp and condensation will be uneasy bedfellows with gypsum plasters.

That would explain what I'm finding.

I've been going through the house making sure that one side of every downstairs wall has lime plaster at the bottom. That seems to have fixed the damp issues.

 

[Lacan07]

I'm kinda leaning that direction myself. With the pink stuff, there is a noticeable change in colour when it gets wet, and then it will slowly turn pink again as it dries. However, gypsum is water soluble, so if the plaster is exposed to prolonged damp, it will turn to a mush. Lime plaster is much better at handling damp conditions, so wins out on walls that lack a DPC or are subject to periods of penetrating damp.

Gypsum does indeed have some degree of breathability.

Its worth noting that standard plasterboard is just as breathable as lime, but what happens to it when it gets wet or damp is another matter entirely.

 

[MatthewC]

There’s a general rule of not going looking for work, and stripping entire walls then replastering is a messy, slow and expensive job than most would avoid if possible.
<snip>

Yes, if you start stripping lime plaster off a wall, be prepared to get VERY dirty - the dust gets EVERYWHERE. The old plaster comes off very easily but then takes ages to replaster with several separate coats (I think we had four), hence also costing a lot.

If at all possible, do NOT do it. Ask me how I know!