Any plasterers on here?

[MinimalistMommi]

We (well the plasterer) are replastering entire victorian cottage built around 1870 - do I need to worry about what type of plaster is used? Does it need to be lime plaster? Something about ventilation or something? if anyone knows anything about this it would be helpful. We're starting with the stairwell.

This is a huge area - where to start!

There are a variety of renders that can be used on wall. Lime renders are usually based on a mixture of lime with aggregates - sand and marble powder are the most common.

Plaster is a render based on gypsum. It is not normally mixed with aggregates, although it can be.

You can also mix plaster and lime (provided you use non-hydraulic lime).

Lime and plaster give very different finishes. The more common interior finish that you paint over is plaster. Lime is more commonly used on tinted renders that you don't then paint over. Which you choose is a matter of taste, imo.

Both lime and plaster are quite breathable. What is not breathable, and is absolutely to be avoided in older properties, is concrete. You would not tend to use this in an interior anyway, except in some very modern ones or in a wet room (sometimes).

Where you absolutely should use lime renders is for renovating the exterior of a period property. You cannot use plaster there, as it is not suitable where exposed to the elements, so your choices are lime or cement based renders. The latter are not sufficiently breathable for period properties and can lead to humidity problems in the future.

Hope this is even vaguely helpful. Let me know either way .

Liara thank you
So basically for our interior the plasterer will use a bog standard plaster? Is that right? We will be painting over it. I really appreciate you getting back to me. I was doing a bit of research online and read this www.channel4.com/4homes/buy-sell/buying-property/property-styles/styles-of-architecture/victorian-08-06-26/display/page/2 and it worried me that a certain type of plaster might need to be used.

We own a similar property. If there is any damp in the walls then lime plaster is better as it tolerates damp and allows it to escape or 'breathe' without damage. We have some gypsum which needs replacing as its decayed and crumbled off the wall, due to the damp.
In theory if there is no damp then gypsum would be ok though not 'proper' in a period house.

Avoid cement at all costs, its very damaging and will trap moisture in the walls, this often results in problems in the future.

There is tonnes of info on line. I often use 'period property' as a reference site.

Lime plaster is more expensive and finding a decent plasterer to do it is a challenging, depends a lot on where you are. I recommend a lot more research
before you decide to be sure you choose the material correct for

... your situation. Google SPAB too, society for protection ancient buildings, they have a lot of good advice and info.
Good luck with your house!

Is lime plaster more difficult to apply than regular plaster? Will I need a specialist plasterer to do it?

I wanted to mention we have had high moisture readings on walls so I think we need to use lime plaster. Does anyone know if there are different types of lime plaster? Also will we definitely need a specialist to apply or can someone experienced at plastering be able to do it?

Its easier to apply as it must dry slowly so you have lots of time to apply it, the skill is in getting a smooth finish, we've struggled on the areas we've attempted ourselves.
It uses carbon from the atmosphere, which it can only do while damp, to 'set' hard. Its a completely different process to gypsum which has a chemical set and happens very quickly. If lime dries out before it 'carbonates' then it will be weak and crumble, and need re-doing.

You should find a specialist professional since it needs understanding to be done well and you need to know what questions to ask as some trades will say they know how to do it, but won't!
Its a slow process as you build up layers over few weeks. Its also heavy work due to the sand that's often used in it.
There are different types of lime depending on the situation you're using it in. Natural or non-hydraulic lime and several strengths of hydraulic lime. I'm not an expert but have looked into this for our own house.

Try and find a specialist plasterer and quiz them about it. Also do you know why the walls appear damp? There is a lot of info about damp online also!

I don't have any experience of victorian cottages, but from what you have linked to it sounds like they would have just stuck a lime render on the wall and then wallpapered over - they would have done this as it would have been much cheaper.

Yes, lime render is harder to work with than plaster. The reason is that you basically can't really rework it. You have to get it right first time, unlike plaster which you can rework for ever. It then has to be kept in the right environment (not too hot, not too cold, not too wet, not too dry) for up to 6 months for the full carbonation to occur. In the meantime the render will continue to feel soft, and if you knock it you will leave a hole in it. Which you will never be able to repair seamlessly.

I personally think it gives a lovely effect (there are loads of different types of finishings that can be done with it). But it would be terribly annoying to use a render like that and then go stick some wallpaper or paint on it.

What is currently on the walls? If they are already plastered with gypsum you would have to remove all that before putting up a lime render too.

Sorry, forgot to say that my second paragraph applies to non-hydraulic lime, which is the really breathable one.

Hydraulic lime sets faster but is much less breathable.

Render is used outside. Plaster inside. I disagree with re-working lime if that's what you mean. Its gypsum that cannot be re-worked.
As I say, research is the key.

Sorry if I'm using the words wrong, I'm ESL and live abroad, so not necessarily completely accurate with regards to specific terminology. Here we call anything that is applied onto a wall a render, plaster is a gypsum based one.

Gypsum can be reworked forever in the sense that even after it is set it can be patched with more gypsum and made seamless. You can also sand it to remove bumps, and fill hollows with more gypsum. This is not the case with lime, the seams will always show once it is set.

So, I contacted a local to us specialist lime plaster last night (has been doing it 15 years) and the cost was horrific, estimate of £1,500 per room he said as our terraced cottage was built 1870 it would have had lime plaster. I described the plaster I had found on removing wallpaper (blue/grey/green) and he's said that was original lime.

The whole house is wallpapered, under wallpaper is areas of modern plaster skim and large areas where old (lime) plaster was left.

Damp: we had high moisture reading on walls, we had ukdamp.co.uk come in who were great and said it was due to raised ground levels outside. We had extra air bricks added front and back and a drainage channel at front of house to soak water away from bricks.

So making another phone call today to another (25 yr) lime specialist, I hope I'm not horrified about the price again.

Before all this happened I wanted lovely white walls. Will I still be able to have this with lime plaster? Will a lime wash make it white?! Clueless here. I was originally going for a sharp, modern look with a great finish with gypsum plastering so I guess I will get a different look with lime. Will it be more rounded and not as sharp if that makes sense? Will it look ok?! We were going for a 'modern cottage' look with woodburner, wooden floors, rugs, cottage style doors etc Will the lime plaster look nice with what I had in mind?!

Not being funny, but Mr Specialist Lime Plasterer does have vested interest in telling you you need lime plaster....maybe consult a normal plasterer too? Someone who comes recommended and has experience with old properties...

mummy I think it's going to be quite hard to find a plasterer to give an honest answer really, plasterers don't like working with lime because it is much more difficult to use than gypsum plaster

Maybe I need a start another thread on this with a better title to see if any mumsnetters have used lime plaster.

You can get just about any finish you want with lime plaster - it can be ultra-smooth, shiny, as white as you like and so on.

Lime itself is white, much more than gypsum, it is the aggregates that give it colour.

If you go with a marble powder untinted finish, you will get it very white indeed.

But it does take some considerable skill to apply it very smoothly.

Re the damp, was the wallpaper staying on OK?

I feel that most regular plasterers will tell you gypsum is fine in every situation as they are unfamiliar with lime and its benefits. Those who work with lime are sympathetic to old buildings and their problems.

I also prefer the look of lime, it would give a lovely soft finish to the walls. Maybe search for some local properties (thinking National Trust) that have it so you can see the finish?

earlygrey totally agree with everything you're saying! People say gypsum is fine due to lack of knowledge about old buildings, even the tiniest bit of research as shown me I need to look into this and consider what to do. I know price will be a issue too so I guess I'm going to have to see what happens.

Li thank you very much for telling me about the finishes! that is very useful. We originally were going for very white with regular paint before lime came into the equation. So I am after a very white finish and preferably smooth too! I think the softer look should look ok? It's a terraced workers cottage in the city though.

We're pretty sure we going with lime now, need to decide whether to lime putty or hydraulic lime

Anybody know which one is 'better' or is it a case there are benefits to both? From what I can see hydraulic lime will set a lot quicker than lime putty.

Technically, putty which is used to make up hydraulic lime, is more breathable and is (i think) preferred by conservationists. Hydrated lime is used when it needs to cure under wet conditions. I think hydraulic would be good in your situation but your plasterer will advise you better.

Hydraulic is much less breathable.

Lime putty is one of the forms of non-hydraulic lime. More commonly used for fine interior finishes, it is more expensive and takes much longer to set. Non-hydraulic lime also comes as a powder, but it is harder to achieve a truly smooth finish with powdered lime than with putty.

Hydraulic is more commonly used in exteriors, although in olden times it would be non-huydraulic everywhere, I think. Hydraulic is a more modern invention used to replicate some of the benefits of cement (faster setting, and the ability to set in the presence of water).

Um, Liara, I think something is getting lost in translation here. In the UK our terminology is quite different from that which you are using, and I think things are getting confused.

This might help:
Plaster= the material used to cover interior walls
Render= the material used on exterior walls( on the outside)
Mortar= the material used to glue brick /stone together to build a wall (well, it isn't strictly a glue but that's where it goes)

All three were made with lime until the 1890s. After this, cement gradually became more popular and eventually became virtually universal by the end of the 1950s. Buildings originally made with lime should be repaired/ refurbished with lime- because of the construction technology, if you substitute cement or gypsum where lime ought to be used, you will almost certainly get damp problems.

There are 3 main "types" of lime in the UK:
Hydrated lime, also called bag like or builders lime. Avoid this like the plague, it is intended for use as a plasticiser in cement mortar and is not useable for lime mortars, renders or plaster (unless you want a powdery mess that will fail within months of being applied)

Natural hydraulic lime. This is a dried powder which is mixed with sand and water to make plaster, mortar or render. It is classified by its NHL number. 3.5 is usual for most applications, 2 is suitable for sheltered situations, 5 is used in continuously wet or very severe environments ( lighthouses and canals were made using this for example)

Lime putty (occasionally called non hydraulic lime, but not often) This comes as a putty and is mixed with sand to make mortar or plaster, occasionally render but less commonly used for this. Many lime plasterers consider it to be the best for interior plasterwork, and personally I tend to agree.

Lime putty and NHL lime are a specialist material and only available from a few specialist producers. You won't find it in Jewsons! Similarly, lime plastering is a specialist job and the plasterers do command high wages, which makes it expensive.

For your situation, I would say you definitely need to use lime plaster. The price you said per room doesn't sound too outlandish to me, but it is always worth shopping around and getting several quotes.

Sorry, that is long! But specifying this sort of thing in traditional building is my job, and I can bore for England on the subject! Hope it helps....

Thank you Ker for all your information! you have helped a great deal! Another lime plasterer has just rang me and is coming tomorrow night, I wonder what he is going to suggest...the man today who wanted to use three types of Unilit NHL was saying something about salt seeping through and if we used lime putty this could well happen and leave brown staining- he was quite anti lime putty but I'm guessing that is because NHL is quicker and easier to apply?
I'm on tenter hooks about tomorrow night now, getting this right is really important to me.

Nothing is lost in translation, but perhaps traditional building with lime is more common here than in the UK, so many more products are available as standard in builders' merchants, and the use of it is not restricted to specialist artisans.

We have non-hydraulic lime here (CL) in both powder form and putty. Powder form can be hydrated to form a putty which can be mixed with either sand or marble powder to make stuff which you put on walls, which here can be inside or outside. But for most fine work indoors we prefer putty.

We also get a special powder form of non-hydraulic lime from Morocco which does not require any additives and is used for a finish called tadelakt. This does take some very specialist skill to apply.

We have NHL, which is often used for the making of mortars and for exterior renders, but can also be used as an undercoat on interior walls before a finer finishing coat based on CL is applied.

In interiors in this region a very common finish was to use gypsum mixed with CL, which looks just like modern gyspum plaster but is harder and more breathable.

Sorry if I'm rabbiting on too much and off topic OP, I actually really love working with lime (and plaster, though less so) and can get a bit carried away.