I am just about to attempt to have a first go at plastering a fairly large lath & plaster wall. I will have to divide the wall into sections and I am wondering what is the best way to join the sections. Should I try and feather the sections, or make a stright line break point between sections ? I have read one post which suggested making a straight linr break.
Any help or suggestions will be greatfully accepted as it is a daunting enough task without having to do things the long way around.
Are you really going to replaster over the laths? That's OK if you have a historic property and you want to restore it in the traditional way, but for anything else it would be *much* less work to remove the laths and fix plasterboard and just skim over that.
If you do it in sections, each section will need to have a vertical batten flush with the plaster finish, to rule off. When the plaster has set this batten is removed and used for the next section. Alternatively you could use galvanised plaster stop beads on each section, but these would be permanent.
When I had a similar situation my plasterer, I know I should have DIY'd it, found the supporting frame work through the plaster and lath and screwed plaster board on and skimmed it. I lost maybe 1/2" of the room but it was much cleaner than removing the old plaster, but not as much fun, and probably added a bit more thermal insulation too.
You should plaster it in two coats. The first coat is called a 'scratch coat' and you don't try to get a good finish with that one, all you want to achieve is a layer of plaster squeezing between the laths to get a good key. You then scratch the surface and let it set. The second coat makes a continuous, flat and possibly plumb surface. If you want perfection then put on a third coat.
The first coat takes longest to do but it doesn't matter if you do it in sections cos it will get covered and the finish is not important. On all but the largest walls you will be able to do the second coat in one go which will give the best finish but if you can't then make a straight line break not a feather.
Lime plaster with plenty of hair in it is the traditional material. I don't know if gypsum plaster will work cos I've never tried, but the hair is a vital ingredient to give it tensile strength
Anna ~~ Anna Kettle, Suffolk, England |""""| ~ Plaster conservation and lime plaster repair / ^^ \ // Freehand modelling in lime: overmantels, pargeting etc |____|
The scratch (base) coat doesn't matter (or are you just skimming?)
For the finish coat, I work in vertical strips, covering as much width as a bucket of plaster can. I feather each strip into the previous one which works only if the previous one is still workable. If it's going to be an hour or more between strips, you can't really feather and you'll need to cut a clean edge. It doesn't need to be a straight line (actually, a straight line can show more afterwards, depending on decorations and how well you join it).
Yes, good idea - I've done the same on my upstairs ceilings. I just assumed from his message that the OP had already removed the old plaster - dunno why I did that now! :o)
I am just skimming using MultiFinish, but I find that it goes off very quickly,hence restricting me to small areas. I am applying 2 coats of skim, as I have read posts that suggest it is not possible to get a good finish with just 1 coat. I am putting on the second coat after the first one has gone off.
I am hoping to paint the walls afterwards, so I need a reasonable finish. There is more to this plastering lark than meets the eye !! Looks easy, but reality is different. I suppose the only way to get better is by actually doing the job.
Yes -- it's exactly the wrong time of year to be learning plastering ;-) At least make sure your plaster is new -- the longer it's been sitting around, the faster it goes off.
You might want to practice in the cupboard under the stairs, or the garage wall, or similar first. I and others have posted a few long articles about how to do it over last couple of years.
First coat does not have to have completely gone off -- normally you recoat as soon at you've finished the first coat. However if it has set and dried (i.e. next day), then you will need to PVA the first coat before applying the second.
Yes, and don't start with the most important wall in the house!
One coat of finish is fine. I expect the problem you have is that the lime plaster is sucking the multi finish dry very quickly. Is the plaster you've got in your pail or on your spot board "off" as quickly as the stuff you've put up? If so, the plaster's *old*. Try applying a coat or two of diluted PVA (1:5 PVA:water). Let the first coat dry, skim before the second coat has dried. You will do best to skim the whole lot in one go, you will get a better finish.
"Lobster" wrote | Anna Kettle wrote | > Lime plaster with plenty of hair in it is the traditional material. | So do you (or anybody else?!) use hair nowadays? | Just curious!
I use hair to cover the top of my head.
I was wondering if one could ask at the hairdresser's for a sack of (human) hair clippings and add that to the mix, or whether it had to be horse hair.
I do indeed. I do quite a lot of repair lime plasterwork work onto laths and as they are slightly flexible the hair is an important feature.
I know some plasterers who use hemp instead of hair and I have heard of fibreglass being used too though I can't imagine it is pleasant to use but it has the advantage that it doesn't rot if it is left in the tubs of wet lime mortar so tons of the haired mortar can be made up at a go. Using hair, I have to add it to the mortar on a daily basis
Anna
Anna ~~ Anna Kettle, Suffolk, England |""""| ~ Plaster conservation and lime plaster repair / ^^ \ // Freehand modelling in lime: overmantels, pargeting etc |____|
Human hair isn't very good partly cos it is weak to begin with but also cos a bag of hair from the hairdresser will contain dyed and bleached and very weak hair
No idea. Anyone else know?
Anna ~~ Anna Kettle, Suffolk, England |""""| ~ Plaster conservation and lime plaster repair / ^^ \ // Freehand modelling in lime: overmantels, pargeting etc |____|
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