Check the rendering's still attached. Then, if it is, thoroughly clean it.
I had what looked like perfect rendering on my flat three years ago,
which had been applied a couple of decades earlier, which turned out to
be sort of attached in places, but was mostly staying up due to not
having the energy to fall down. 90% of the tap tests had that horrible
On Fri, 22 Jul 2011 13:22:43 +0100, John Williamson wrote:
That is exactly the description of what I found on one of the gables
here last summer. With the exception that a few square yards had
found the energy to fall off in the previous winter.
Got proper scaffolding put up and put a chisel behind it, it would
come away in great chunks. I never really worked out why it had been
rendered in the first place, the pointing was 99% good and the stones
in good condition. I suspect it failed as who ever put in on didn't
remove the paint that was there first so when the paint's bond to
stones or render failed...
I pressure washed the entire wall with an ordinary domestic pressure
washer and "dirt blaster" jet. That removed most of the old paint,
algae and anything else loose. Found a few weakness's in the
pointing. Patched that up and painted with Dulux Trade Smooth
Masonary Paint, it's surived one winter and looks pretty good.
On Fri, 22 Jul 2011 11:53:19 -0700 (PDT), harry wrote:
The test for "powdery" is doe you end up with the old paint on your
fngers if you rub it gently. Even then I'm not convinced that a
stabilising solution is any better than a slightly diluted first
coat. IIRC the first coat I used last year (and this when I've
finished the patching) was about 10:1 paint:water.
Brush is damn hard work if there is any texture to the surface and
tedious in the extreme. Rollers work but you need a decent one. Dulux
Trade Heavy Duty Woven Sleeve(*) worked and lasted well, two and a
half two storey gables with two full coats on smoothish pebble dash
and stone. The dilute first coat was brushed. I don't think that
roller was quite dead but was starting to moult a bit quicker than at
the start. Give a new roller, no matter the make, a good washing and
scrubing before use to get rid of any loose pile.
(*) Be aware that roller is a 1 3/4" core the sheds sell frames for
rollers with smaller cores...
I found if painting textured render (i.e. like stipple finish or
roughcast), those small 4" wide rollers can be good. Often you can't get
enough force onto a full width one to work the paint into the texture,
and the small roller works faster than a brush.
Thanks to all for the tips. I followed the advice about pressure cleaning
and then using a diluted coat. It all seems to make good sense.
They say that a lick of paint hides a multitude of sins. Well this paint
job actually seems to have shown up a load of sins - like what a amateurish
rendering job it was. I think I may have to apply a coat of really thick
textured emulsion to try and disguise the patchiness of the cement
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