Breathable Plaster?

[jungle_jim01]

Hello. I've begun the dusty work of removing old plaster which has blown off the wall (a mixture of recent and lime plasters). I'm wondering about replacing with breathable plaster. I'm sure that there are a lot of folks who will shout that i should use lime, but presumably a modern plaster will be easier to work with? I've spotted lots of 'breathable plasters' on the market, so any recomendations? Also presumably i only need breathable plasters on the external walls?

Cheers

 

[jungle_jim01]

oh yeah...and also...any thoughts on insulation + dry lining these walls? thanks in advance.

 

[FamilyWiggs]

Jim - I think you're missing the point of the forum! :wink:

Although you are of course correct, that there is not a significant benefit of breathable wall coverings on internal walls if everything is dry and no condensation, etc. However I would add 2 points:

a) lime plasters are soooo much nicer to look at - much nicer texture, and you'll know you've done the right thing (a bit like the detail on gargoyles on the rooves of churches - where no one except the stonemason will know how good the workmanship was);

b) I find lime plasters soooo much easier to work with than modern plasters - they are much more forgiving, and much easier to get a good finish; plus you have days to work them and rework them to get the finish you want, not the frantic rush you have with pink carp.

 

[jungle_jim01]

interesting...i've no experience at plastering at all, however, my girlfriend has just begun a plastering course...do you think the skills in modern plastering will be transferable? thanks for the advice

 

[FamilyWiggs]

I've done both but am certainly not an expert.

Gypsum is hard to do well (the only job I've ever bought in was someone to plaster a ceiling before I knew it was evil stuff) and very easy to do very badly.

Lime plaster is a different technique, more pushing and pressing and smoothing is required, than float work as with gypsum. Although you can get a perfectly flat glass-like finish on lime if you float it carefully when it is drying.

Gypsum is faster and more stressful work than lime which you can keep coming back to over days. You need to keep pressing out the cracks and keeping it moist until it goes fully off. Some people think this is extra work; I think it is extra time to get it how you want it.

 

[MatthewC]

... presumably a modern plaster will be easier to work with?

Why should you presume that? It sets very quickly, and so you have to get it right almost first time. My plasterer certainly agrees that lime is much easier to work with (as FW says), especially if you buy it pre-mixed.

interesting...i've no experience at plastering at all, however, my girlfriend has just begun a plastering course...do you think the skills in modern plastering will be transferable? thanks for the advice

As far as the skill of applying it goes, yes, it's transferable. My young-ish plasterer said that he hadn't done much work with lime since his training but he loved working with it. He has shown considerable skill with the application, and we have educated each other about the techniques and timings specific to lime. The finish is superb - if you are near Oxfordshire, PM me and you can come and see it.

If your plaster was all blown, do you know why? There must have been some dampness/water ingress - has it been fixed? Otherwise you will be wasting your time whatever you do!

NB Of course, if your house is listed, you would need LBC not to use lime plaster, which I would not count on getting.

Matthew
http://houseintheenchantedforest.blogspot.com/

 

[jungle_jim01]

Good point about the reasons for it blowing. It was originally damp from a leaking pointing. I've repointed in lime mortar and all damp has dried out. I understand and believe in the lime point of view, but just weighing up the options against practicality, time, and financial constraints. Is there any reason not to dry line the walls then skim with lime?

 

[Feltwell]

Dry lining is quite quick, relatively easy requiring only a basic skill level and it's cheap, but there are several points against it:-

- It's not breathable. There's no point in skimming with lime - you might as well do it in gypsum. If you were going to use lime for the surface finish then you'd need to buy a product to enable you to skim over the plasterboard.

- It will give you a perfectly flat surface which will in all honesty look wrong in an old house. A few imperfections are good!

- It feels cheap & nasty in my opinion. Go and have a look round any new build, tap the walls and you'll see what I mean. Do you really want the "Barratt Box" feel in your lovely old house?

- It's a pain in the @rse when you want to hang anything from it. Pictures are OK, but putting up shelves and the like can be a right pain. You drill through the plasterboard and into the wall behind, fair enough - but then you need to be very careful not to crush the plasterboard as you put your shelves up, as unless you are exactly over where a dab of adhesive is behind then there is a void that you'll just push the plasterboard into.

- Plasterboard does not like the wet, at all. I've had pipes leak above lath & plaster ceilings, apart from surface stainings there was no ill effect. Above plasterboard and I've needed to replace sections. What if your damp has not fully gone away? I'm presuming your internal wall is bare at present, so is breathing nicely internally as well as externally. Even plastering with lime will reduce that breathability, but nowhere near as much as with plasterboard!

The above is of course ignoring all the arguments about keeping an authentic finish in your old house. Personally, I tolerate plasterboard for ceilings if the original is totally beyond repair or (as in my case right now) an insulated plasterboard ceiling below the original lath & plaster is the only way to improve the insulation of an attic room to an acceptable level, but for walls I would always wet plaster every time unless there was a very strong reason not to do so. Even for ceilings, whilst I'm not committed enough to replace my existing plasterboard ceilings (done by previous owner) I would always look to repair lath & plaster first if at all possible.

 

[jungle_jim01]

Thanks feltwell for the comprehensive reply. That answers a lot of my questions. I've actually got the same...an insulated plasterboard attic ceiling. I'm definitely thinking it's worth the effort with lime plaster. Can i ask what you've done with your ceiling though? gypsum? or some kind of coating followed by lime skim to match the walls? cheers

 

[jungle_jim01]

also...presumably it's worth using a breathable paint too?

 

[MdB]

One of our old walls was covered in multiple layers of cement and tanking gunk. It was still damp. The other old wall was covered in multiple layers of cement and then dry lined. As the wall was still damp, the plasterboard got damp as well which meant it fell to pieces at the bottom (and was famously repaired with a piece of cardboard and then wall papered over). When we came to remove the dry lining the wall underneath was just black with mould apart from the one small section which was ventilated and fine. Our solution to this was to remove the dry lining, the cement and the cause of the damp (high ground levels outside) and now have a dry wall.

 

[Feltwell]

Thanks feltwell for the comprehensive reply. That answers a lot of my questions. I've actually got the same...an insulated plasterboard attic ceiling. I'm definitely thinking it's worth the effort with lime plaster. Can i ask what you've done with your ceiling though? gypsum? or some kind of coating followed by lime skim to match the walls? cheers

I'm skimming my ceiling in Gypsum, or should I say I'm getting an experienced plasterer in to do this one - lots and lots, and lots, of angles in this room!

Why gypsum? It's on plasterboard - I don't see the point in using lime in this case, it will just add to the cost. The walls are lime plastered and are being filled & repaired, but will still need finishing with lining paper before they are painted so the surface finish isn't so much of an issue.

I really don't like doing this, but undercladding the existing ceiling with insulated plasterboard was the only option to improve the insulation in what was a rather cold in winter and hot in summer attic room. Insulating between the rafters when we had the roof off did make an improvement, but it needs more in my opinion, so a compromise has to be made especially as it will be a child's bedroom.

If you want to skim over pb with lime then someone posted up recently that Mike Wye sell a paint-on product to enable you to do this.

also...presumably it's worth using a breathable paint too?

Breathable paint is only worth using if everything else is breathable - if any 1 element beneath it is not breathable then there's no point. Breathability doesn't matter on your ceiling, only on your external walls. BUT - many people like the soft, "chalky" finish that many of the more traditional breathable paints have. Modern emulsion on your ceiling next to limewash on your walls might look a bit odd. Also consider what the room will be used for when you make your choice - limewash can rub off for example, not good for walls in a kid's room. More durable breathable paints include ones like clay paints - other on here will have more knowledge than me on surface finishes.

My personal opinion is that dry-lining walls should be avoided wherever possible. I have used plasterboard for walls, but only on a more modern house where I was constructing stud partitions and lightweight construction was a must.

In saying all this, I'm presuming that your house is not listed so you have a free choice of what to do. I'm talking purely in practical terms here - if you want to have an authentic finish to your walls then lime plaster is the way to go, without question.

 

[MatthewC]

Dry lining ... will give you a perfectly flat surface which will in all honesty look wrong in an old house. A few imperfections are good!

So my plasterer is doing the skim too well?

If you want to skim over pb with lime then someone posted up recently that Mike Wye sell a paint-on product to enable you to do this.

It's called "DG27" and it is amazing - but also very expensive!

 

[Feltwell]

So my plasterer is doing the skim too well?

I don't know why but I can always tell the difference straight away, without tapping any walls, between a wet plastered and a dry lined finsh, even if the plasterboard has had a skim. The only reason I can think is that a wet plastered finish back to brick/stone, even if done very well, may be very smooth but isn't always flat if you put a straight edge across it - especially at internal corners.

On the other hand maybe I have strange psychic visual wall-penetrating powers and should be trying to get my own series on Channel 5 ! (They show worse, let's face it!)

My comment was more as I seem to remember Jim's place is a bit older than yours or mine. But I may have remembered that wrong.