Hi,
I have to plaster a bare patch on a brick wall. What is the best way for joining the new plaster to old one?
Should I have a sharpish vertical cut of the old plaster towards the bricks (it is quite crumbly and easy to remove with a scraper)
or
should I let it be feathered as it has come off (remove lose bits)?
I am going to use undercoat and finishing plaster.
TIA Charles
IMHO just tease off anything obviously loose and donlt worry about straight edges - they would tend to be more noticeable when patched.
Cheers Jim K
You can't really feather plaster.
Spot on - the eye is extremely good at identifying straight line imperfections. A random jagged edge should be a less noticable imperfection.
PVA (dilute) the bricks and the broken plaster edges first. You want to use a scratch (under) coat to about 2mm behind the finished surface, and then finish coat to bring it level. Apply finish coat whilst scratch coat is still wet, and ideally before scratch coat completely sets.
Andrew Gabriel said the following on 27/07/2010 23:00:
Yes I will do that ... I might have to randomise it a bit more.
what dilution roughly?
Thank you for the last bit. I would not have done that :-(
C.
Not very critical, 4 water to 1 PVA should be fine. Add the water to the PVA slowly initially whilst mixing, as a dollop of PVA in water doesn't mix easily. You can buy it pre-diluted in 5l containers.
Bonding coat is probably the easiest scratch coat plaster to use, as it contains glue too, so it sticks easily to almost anything (including your plastering tools if you don't wash it off well).
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