Hi,
Thank you for these amazing videos. I am plastering a room and have a couple of questions.
Part of the wall in an alcove has blown, so I think it is best to break the blown wall off and use a Bonding Coat then skimmed with multi finish.It is only about 60cm by 100cm.
1. Is bonding plaster best for old brick as a backing coat?
2. Can I use my finishing plaster trowel? (I do not want to damage it for the finishing coats.)
Answer
Bonding coat will work well for this kind of patching up - as long as the wall is not damp. If it is dry - then all is good. Carefully remove the old plaster and gain a good edge by slicing away any rough plaster with your trowel or a knife to ensure you do not disturb the bond any more than you have to.
This edge will probably very porous and may need soaking with lots of water - otherwise the moisture will be sucked out of the new plaster so fast that it may crack away. Then apply the Bonding Coat and rule off and then carefully push the edge in to allow room for the finish coat to join flush to the existing plaster - if you are just patching. However it depends upon how big the alcove is - as it may be worth thinking about putting the Bonding Coat plaster in flush and then apply PVA to the whole wall and skim the whole wall. This can sometimes be quicker than trying to achieve a seamless join.
It is definitely okay to use your finishing trowel - just be careful with it - using it as normal it will be absolutely fine - just be careful when scraping the floor and avoid nails that could nick the edge.
Let me know how it goes
Paul