Lime plaster over plasterboard

[tumbledown]

Yet another question - I know they are coming thick and fast from me, but as a novice taking on a major renovation job, I have plenty of them!

Can you sucessfully lime plaster over plasterboard? you may ask why I would want to! The internal partition walls upstairs are just studwork and plasterboard. with all the other jobs I have to do, I can't afford to take them all down and replace with something more traditional like lath and lime plaster. But I really do like the look of lime plastered walls. Would the lime plaster stick to the modern surface? quite a few of the walls have been left unfinished, that is, no render at all (I think they started to renovate but gave up!). I have been removing the cement render from the outer walls to replace with lime render, and I know leaving the plasterboard is a bit of a cheat, but they are not really affecting the historic structure of the building or causing damp problems, so I consider their replacement as low priority compaired to some of my other problems!

Another question: I'd like to try and do this work myself, but I'm not sure how easy this is for a novice. I've been reading up about it and it doesn't sound too difficult to get the hang of (famous last words!).

Does anyone have any tips oe do's and don'ts for the beginner? Would you buy the lime putty/hair/sand etc seperately and mix your own, or go for a ready mix version? (I've been looking at the Anglia lime web-site at the ready mix products and they are not too far from me).

 

[skier-hughes]

When I get around to starting my plastering I'll be buying ready mixed to begin with, and as I gain more experience I'll move on to mixing my own.

As for plastering onto plasterboard, my local lime supplier does a special mix just for this. I've not used it, and only remember it from a conversation we had when discussing lime, so maybe ask at Anglia Lime?

I intend to try doing it myself first, because I enjoy doing things like this and it give me great satisfaction in knowing I've done it. I'm also not inclined to keep going and going at it with no success. If I find it's something I can't master, I'll get someone in to do it, and move on to trying something else.

That's my beginners eye view on it.

Graham

 

[tumbledown]

Thanks Graham - sounds a very sensible approach, why didn't I think of that! Thats good news about a special mix for plasterboard - I'll make some inquiries. Its the ceilings I'm not looking forward too ......

 

[Ian Bond]

Hi

You could try this stuff:

http://www.mikewye.co.uk/dg27tech.htm

I'm going to do this myself, as my attic and kitchen ceilings are plaster boarded over the original lath & plaster. There's no way I'm pulling down the ceilings just to redo in lath and plaster, so to me the best compromise is applying this DG27 stuff and skimming with lime.

One reason I love lime plaster is you have more time to work it to a decent finish than with gypsum. Having said that plastering is still a hard skill to learn but well worth having a go. Especially if your house has wobbly walls anyway - my plastering blends in beautifully, whereas a perfect flat finish would stick out like a sore thumb.

Initially I mixed my own lime putty from bagged hydrate, and made up mortars and plasters by hand. But as the jobs stacked up, I've gone for the ready made stuff. More expensive, but less work and hassle.

 

[Ian Bond]

Oh get the hair separately and mix it in as you need it - the lime will dissolve it if you leave it in the wet mix for long periods of time.

I should have made the effort to go on a lime plastering course - instead I experimented on my house, and as a result ended up redoing some of my earlier work.

And wear safety specs to keep the stuff out of your eyes.

 

[tumbledown]

Thanks Ian. I thick I'll go for the ready mix - at least until I'm used to the stuff. I have ceilings that need doing too, but I think I'll practice on the walls first.

 

[rshartley]

I used the DG27 product on my recent renovation and it worked well. You can use it as a primer over all sorts of substrates and then skim over with finishing plaster. I even used it on the MDF walls of a newly built airing cupboard and (for speed) I limewashed straight over it with no plaster involved. I intend to skim it when I get the chance.

I mixed some of my limewash pigment into some diluted DG27 and used it to paint some radiator pipes too. It's really useful stuff but not cheap.

My approach to DIY lime plastering was to buy Jane Schofield's little green book, a couple of SPAB publications and Mike Wye's DVD. All of these were useful for starters and then I attended a day long practical course.

I too bought premixed mortars for convenience and because I wanted to be sure that what I had was going to work the way I needed it to.

I have two tips if your walls are quite wobbly or wavy like mine are:

• 
  1. If using a steel trowel or float, get yourself a Venetian plastering trowel rather than using a conventional one. I found the smaller angled trowel much easier to use.
  2. Don't try to go for too thin a finishing coat or you'll be there all day trying to get a smooth finish

Irrespective of the shape of your walls, I recommend that you never take a strong halogen work light and shine it along the length of a wall you've plastered - it's just too depressing a sight!

 

[NT]

Making your own lime putty is very easy. Bagged lime plus water, mix it to a creamy putty, fit an airtight lid and store it for a few weeks minimum. Its time thats the difference.

Also I would always test lime putties before use, as it is posible to get a bad batch that never sets.


NT

 

[Ian Bond]

I too bought premixed mortars for convenience and because I wanted to be sure that what I had was going to work the way I needed it to.

never take a strong halogen work light and shine it along the length of a wall you've plastered - it's just too depressing a sight!

Very true

It takes years of practice and a high degree of skill to achieve that authentic wobbly plastering, perfectly blending in with the original work.

At least that's what I tell people!

 

[Nigel Watts]

There seesms to be an implication here that lime plaster gives a rustic finish whereas modern gypsum gives a smooth one. Lime can of course give a perfectly smooth and flat finish, with a marble like surface, and this is what is often needed in Georgian or Victorian houses, especially townhouses.

If you want the plaster reasonably flat over a large area you should use a system of dots and screeds. I didnt find this hard to do. The difficult bit was then getting the beautifully smooth surface finish (this still eludes me). The answer I suspect is to use several very thin finishing coats, scrubbing them first with a crossgrain float to get an even distribution of material, and then with a steel float for the polish.

 

[Ian Bond]

It's not that I'm trying to imply lime gives a rustic finish - it's more to do with my amateur plastering technique

I can do just a rustic a finish with gypsum, which usually sets in the bucket before I've got in on the bl**dy wall. A very expensive way of DIY plastering, as most got chucked away.

In fact, I can get a far flatter and smoother finish with lime, as there's plenty of time to work it, compared with gypsum.

My house is a vernacular building with wobbly walls, so naturally that;s the finish I try and achieve!

 

[Gervase]

Lime plaster will stick quite happily to plasterboard provided you whack on some of the dreaded PVA first. As the board isn't breathable it's not going to matter if the plaster is laid onto PVA and it will help it bond.
As for smoothness, dots and screeds is the way - and a good long feather-edge. Get a lightweight aluminium one rather than heft around a wooden job, and it will let you get your walls a plumb and true as you fancy.

 

[tumbledown]

Thanks for the tips Gervase. But, at the risk of sounding stupid, I have no idea what "dots and screeds is the way - and a good long feather-edge" means. I'm afraid as a complete novice they are terms I've never heard before. Could'nt give a brief idiots guide could you?

 

[Ian Bond]

Lime plaster will stick quite happily to plasterboard provided you whack on some of the dreaded PVA first. As the board isn't breathable it's not going to matter if the plaster is laid onto PVA and it will help it bond.
quote]

That sounds like a cheaper option, Gervase.

It's got me wondering how 'breathable' standard gypsum plasterboard actually is?

I think you can get a foil backed sort - is that to provide a vapour barrier?If so, it seems to suggest that the ordinary stuff lets water vapour through.

The DG27 stuff is supposed to be breathable, and I'm not sure why that's necessary if it is to be applied over non-breathing substrates.

So perhaps the easiest thing to do is go for the PVA (diluted?)

Ian

 

[CHRIS]

I hate to say it but the British Gypsum White book is a great way to learn about various modern plaster boards and finishes etc, have a look at their website and go through the cataloge.

You will be able to go into the builders merchants and not sound like a Sunday DIYer!!!! also tells you about coverage per bag etc (big help when new to this game).

The other option is to add some PVA to Limewash as Per "Interlime" from Trad paints in Hitchen

http://www.british-gypsum.bpb.com/immediacy-217

 

[NT]

Gypsum plasterboard soaks up water like a sponge, so I guess its very breathable. (When wet it can be bent.)

NT

 

[Sue Wilkinson]

Another question: I'd like to try and do this work myself, but I'm not sure how easy this is for a novice. I've been reading up about it and it doesn't sound too difficult to get the hang of (famous last words!).

The Lime Centre (is that the same as Anglia Lime? certainly in the right direction for you) runs lime experience days, I would heartily recommend you go on one for plastering. You learn a lot, and you get the chance to practice with experts on hand to stop you doing it badly and to answer your questions. You will get home ready to go.

I have attended such days for pointing and plastering, and they both increased my confidence so that I knew how to do it. There's been no stopping me since and I now get paid by fellow villagers to do it fo them. Bob Bennet is the main lime man at The Lime Centre, never met him (I did my experience days at IJP near Reading), but spoken to him on the phone, he's a mine of info, as is Mike Wye.

I recommend you buy the ready mix, until you are comfortable with what you are doing this is a worthwhile extravagance. Don't buy it haired though, by the hair seperately and add when you want to use it. You need Jane Schofields little book about lime (see the book section of this site) for the line drawing of how hairy to make the mix, basically much more than you think.

Its not difficult, but you need a bit of technique and some confidence.

Hope this helps.

Sue

 

[Ian Bond]

If you're rendering (plastering onto a solid substrate, such as stone) I've found that you need a lot less hair in the mix than for lath work - otherwise it won't stick properly.

Tumbledown - if you're skimming over the plasterboard, you won't really need to add hair (although fine, white hair can be added to finish coats).

Mike Wye's site recommends a 3:2 mix of fine sand to lime for skimming plasterboard - that's something I'm going to have to remember when I do my plasterboard ceilings. I usually use a less lime rich 2:1 mix for skimming over lime backgrounds.

http://www.mikewye.co.uk/mikeprices.htm#limeplaster

 

[rogerh]

I have no idea what "dots and screeds is the way - and a good long feather-edge" means.

Me neither but this explains it:

http://www.stucconews.com/questions/question2001.html

 

[tumbledown]

Thanks for the URL Roger - although I'm still not sure I fully understand it, but at least I've got a better idea of whats going on!