lime plastering - expected costs vs gypsum

[Stephen Fasham]

I have an 18th century house (no DPC) which is lime plastered on the inside. I am doing quite a lot of work to the house and need to get quite a lot of plastering done. I was planning to use lime plaster on the ground floor, and the ordinary gypsum stuff on the upper floors where damp is not an issue. Does anyone have an idea of how much extra the lime plastering will cost, and should I persuade a plasterer to 'have a go' or get a specialist?

Please don't suggest that it's easy and I should do it myself, as plastering is the one and only job I'm NOT doing. Plumbing, wiring, central heating installation, bricklaying etc. YES but plastering NO!!

Fash

[Andy]

Take a look at

are many useful articles and a list of specilaists in all areas. Also try you local conservation officer at the council. In my experience it probably isnt worth trying to persuade a plasterer to have a go. Although they would certainly possess the neccersary skills most will think that you just want some builders lime (hydrated lime) added to ordinay gypsum stuff - this is not what you want.

[Peter Taylor]

ordinay > gypsum stuff - this is not what you want.

Maybe I'm wrong, but can't you use Hydrated Lime to make the lime putty? It would work out a lot cheaper probably. I seem to remember at college years ago learning about slaking pits and lime putty mixers

Peter

[andrewpreece]

That's what I've been using to make lime putty/mortar: hydrated non-hydraulic lime. As I understand it in the old days limestone would be roasted to get quicklime ( CaO) then doused with water to get slaked lime ( CaOH? ). I'm pretty sure slaked lime is the same as hydrated lime, so you don't have to contend with dealing with quicklime, which is caustic stuff.

Andy

[Anna Kettle]

You can use hydrated lime to make lime putty (put it in a tub of water overnight to soak) but who would bother these days when a ready prepared tub of lime putty is available ex stock from Jewsons. In the old days ie 5 years ago, lime putty was much harder to get hold of and hydrated lime was sometimes the only easy source.

Quicklime is the previous stage in the manufacturing process so there is no need to bother about that unless you are a keen home lime producer (and there are a surprisingly large number of them)

The Building Conservation Directory as recommended above is a good but expensive source of lime plasterers. It costs an arm and a leg to advertise there so your average lime plasterer (like me) won't be able to justify it. I suggest you speak to the conservartion officer of your local council who will give you a list of local names

Anna

-- ~~ Anna Kettle, Suffolk, England |""""| ~ Plaster conservation, freehand modelling in lime / ^^ \ // Overmantels, pargeting etc |____|

01359 230642

[Andy]

Yes you can use Hydrated Lime to make lime putty but this is considered inferior. The point I was making was (in general) builders/plasterers when asked whether they work with lime plasters or mortars think it means adding a quantity of hydrated lime to a gypsum plaster or cement based mortar or render - which is not what is required for period property restoration.

Im interested to here that lime putty is available at Jewsons.

Pity you live in Suffolk Anna. (Pity for me that is !).

[Stephen Fasham]

Thanks for the info Anna, I will ask the conservation officer next time I speak to him. Just for comparison what would your daily rate be? If you prefer not to post it generally please e-mail me (email exactly as posted).

Fash

[John Rouse]

In article , Andy writes

Try asking them if they slake their own lime - it doesn't matter whether or not they do, its the response that counts - "Yer wot" is a bit of a give-away.

J.

[John Rouse]

In article , Stephen Fasham writes

Lime plastering should be cheaper, the materials are cheaper, and any that falls to the floor can be re-used, unlike gypsum (as long as the floor is clean), so there is less wastage. As the plaster can be worked for longer, its easier to apply, the only downside is that it takes longer to set.

Lime plastering is quite different to gypsum plastering - for one thing you're not working against the clock so much.

If you're anywhere in the middle of England, give Dean Hicks in Derby a call, he's done a lot of lime rendering, including quite a few straw bale houses, and our 150 year old pile.

J.

[Andrew Gabriel]

In my experience, the cost of the materials (for gypsum plastering) is quite insignificant compared to the labour cost (like about 1/10th).

No one's mentioned the horse hair yet...

[Anna Kettle]

I charge £20 an hour if I'm doing an hourly rate, but generally I give a price for the job

Anna

-- ~~ Anna Kettle, Suffolk, England |""""| ~ Plaster conservation, freehand modelling in lime / ^^ \ // Overmantels, pargeting etc |____|

01359 230642

[Anna Kettle]

No its not cheaper its more expensive because lime takes longer to set than gypsum and it has to be tended during that time. The tending time adds a certain amount to the bill

Anna

-- ~~ Anna Kettle, Suffolk, England |""""| ~ Plaster conservation, freehand modelling in lime / ^^ \ // Overmantels, pargeting etc |____|

01359 230642

[N. Thornton]

It shrinks and cracks during that time? I ask cos I have this insane idea of trying a small bit of lime plastering one day later in the year. I've never plastered anything.

I was reading up on making the stuff, and I gather quicklime is whats wanted, slaking it yourself. I have some hydrated lime here - is it possible to put it in the oven to dry it out? Or is that nuts? :) I ask because I know lime based dehumidifiers can be recharged by oven heating the wet lime.

I looked up quicklime manufacture, but that process is quite different to just driving off moisture, and I would expect one need not use the same kind of high temps just for drying. I did google but didnt get what I wanted to find out.

Regards, NT

[Anna Kettle]

Yes it will need a light spray and to be consolidated with a float a couple of times. Lime plaster needs CO2 and water to set so you mustn't let it dry out completely in the first week or so. Equally you mustn't drown it or the air won't get into the pores

Ignore quicklime. Buy lime putty from Jewsons and mix it 1:3 with sharpish sand. I think there is a uk.d-i-y lime mortar FAQ

Anna

-- ~~ Anna Kettle, Suffolk, England |""""| ~ Plaster conservation, freehand modelling in lime / ^^ \ // Overmantels, pargeting etc |____|

01359 230642

[Peter Taylor]

N. Thornton wrote

No, this is slightly wrong. The hydrated lime you buy in bags from builders merchants has already been slaked and then dried out again. It doesn't need any more oven treatment. You can soak it in water and make it into lime putty, but it's a long, laborious job and unnecessary if you buy tubs of lime putty as Anna suggests.

If you ever try slaking yourself, remember quicklime is nasty stuff. It is highly alkaline and reacts quite violently with water, giving off heat. Think of the rules when you mixed acid and water at school - you should always submerge the quicklime in the water, not add the water to the lime.

Peter

[N. Thornton]

Thanks for the tips. I've decided though, I'll try a little bit in the oven and slake it, see if it works. If it does I'll do it on a bigger scale later. I'll hopefully incorporate some fibres when I mix it up as well.

I'm not going to travel to Jewsons, which I dont think we have here, and purchase what I have already. Far rather do it myself, more absorbing and less time.

Regards, NT

[Anna Kettle]

Certainly. And then you become a certified limey and get to go to the Buildings Lime Forum Conference and Pissup

and less time.

Unlikely, though I suppose you could be emailing from Mars

Anna

-- ~~ Anna Kettle, Suffolk, England |""""| ~ Plaster conservation and lime plaster repair / ^^ \ // Freehand modelling in lime: overmantels, pargeting etc |____|

01359 230642

[Chris Holmes]

I think there is a uk.d-i-y lime mortar FAQ

I was just about to recommend you as author Anna :=))

[G&M]

Unfortunately yes. A lot in summer, very little in winter. Only don't expose it to frost or it cracks big-time.

Just throw a bag of hydrated lime in a clean plastic dustbin, fill with water (use ALL the safety clothing you can get) and leave for a month, stirring occasionally. Not quite as good as some of the best lime putties but good enough.

[John Rouse]

In article , G&M writes

The problem is that you don't know how long it has been hanging around in the builders' merchants, and how much of the hydroxide has turned to carbonate.

J.