Plastering question

[mildmanneredjanitor]

Can someone give me some pointers?

I have skimmed plasterboard before and got on ok, but I've got to skim a couple of old plastered walls, just wondering what prep I should do before hand?

I've removed most of the loose paint and big lumps of filler and goop , is it best to treat with a solution of PVA before skimming?

What sort of thickness can finish be applied? is it worth hacking out all the old bad repairs and plastering these first with (the undercoat type plaster - not sure of it's name?) I have had to chase out for a new cable anyway.
Didn't know how much can be lost with finishing plaster?

Finally is it worth using a straight edge to get the flatness before finishing with a trowl?? I don't intend to plaster much so don't want to buy a feather edge.

Thanks in advance!

 

[AdamW]

I have read that it is best to apply a coat of watered-down PVA and then skim whilst this is still tacky in order to provide a good key.

Bear in mind that plastering is the one thing I always leave to the pro's though!

 

[DAZB]

Spot on with the PVA first .In general a good skim coat will be about 2-3mm in thickness so it may cover some of the bad spots but if you have large patches of bad plaster then it would be best to fill these with Bonding ( the ' undercoat ' plaster ) and then skim over it all afterwards. It will depend on how good you are with the trowel regarding the need for a straight edge. If you feel you will need one then can you not use a cheaper alternative like a 2 metre length of pencil round skirting board to get the plaster fairly flush before finishing it off with a float ?