A plasterer told me he once started work on a ceiling and it went off
straight away. It turned out the plasterboard had been up too long and
had dried out.
I am just about to skim a couple of small areas, the biggest is 4
square meteres and the board is bone-dry without any smell. It has
been up for a year.
Shall I just go for it, or in your experience, would you wet if first?
If so how?
An alternative to the plastere's big bristle brush waved at the wall is a
pump up garden sprayer - the kind you use for weedkiller.
Filled with clean water this can give a fine misty spray and be used to wet
down large areas quite quickly.
For a small area a hand sprayer (just a bottle with a trigger top) would no
doubt do the same.
I think the hand sprayer is a great idea, it's only a small area.
[I built my extension with the usual cheap Celcon building blocks but
I could never get them wet enough, long enough, with the bucket of
water/paint brush method (in the summer heat). It was more exhausting
leaping up and down painting it with water than applying the render so
in the end I just blasted the wall with a hose pipe.
The original part of the house (1955) used a denser block, whitish,
with a cavity, this only needed a single touch with a wet brush and
you *had* to wait for fifteen minutes or more before you were *able*
...and when new plaster touches old plaster, at least that's what the
literature says so I have always kept everything spotless and thought
it mattered until:-
The chap who skimmed the ceiling turned up and had a good laugh at my
plaster's wheel. He produced a 450 watt electric drill with a paint
mixer. The mixer was covered in old plaster. He mixed it in a large
plastic paint container, about two feet tall and about 9 inches across
that also had old plaster stuck around the bottom.
He mixed up a huge amount so that the thing was nearly full and I
could hardly lift it. By the time I had mixed up half as much again
and staggered in with it, he had most of the first mix up.
So this "remove all traces of old plaster" is a myth? (If mix large
amounts and you're quick).
I don't follow this at all - my immediate reaction was "the plaster's
having a laugh, surely...". But enough folk have responded to make me
think it must be true. Could somebody explain?!
Firstly, plasterboard is encased in paper, so the finishing plaster
has no direct contact with the plaster component of plasterboard.
Secondly, plasterers are commonly required to apply a skim coat over
an old, knackered plastered ceiling to provide a decent finish prior
to redecorating; and you don't get plaster much older than that! So
firstname.lastname@example.org (Lobster) wrote in message
Plaster board is porous. That's why building regs specify foil-backed
boards for ceilings (as a vapour barrier).
Tradesmen are quick, you may not notice the little touches they do
like e.g. damping down, and *that* is the trick.
I am just a fair-weather amateur so everything I do is in the summer.
The mistake I consistently make is too dry e.g. I have to constantly
remind myself "make it wetter than you think" (the bricks, etc, not
If you inadvertantly saturate some bricks, no probs they will be
useable in half an hour (brick-laying-wise), but when a barrow-load of
render falls off a too-dry-wall it is most annoying and hard work
reviving it by hand not to mention a time-waste.
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