repairing plaster in south wales house

[matz]

Is there any chance someone could give me some info re. the following

south wales typical terraced property, rendered? outside with pebbledash. Plastered interior walls. I have hacked off some plaster from around a bedroom window due to damp ingress (now fixed due to leaky gutter) and have to repair hacked area. The walls are solid about 20" thick made from bricks and black mortar and plastered finish is 25mm thick but its not solid plaster.

I'm thinking of using Hardwall 2 or 3 separate coats then finishing plaster on top to blend in to surrounding plaster. I'm looking for an adequate job not a pristine one hence DIYing it but dont want the new plaster to crack or fall off 12 mths later due to wrong materials or techniques.

Am I on the right track with the above as an adequate repair to the damaged area?

 

[stevethespreader]

Use sand and cement as undercoat not hard wall its a solid wall prone to damp

 

[matz]

thanks Steve. I did wonder about Lime. What thickness in one coat can I do the sand/cement?

 

[stevethespreader]

It's up to you if you want to use lime to be on the safe side, just fill it so its a couple of mm short of the existing coat

 

[matz]

strewth this is a difficult subject isnt it. Reading online, never before have I seen so many varying views of how to do a job!!! before starting, where I'm up now to is using sand and cement mix 4 - 1 scratch coat with plasticiser and waterproofer then top coat 5 -1.

Where I'm struggling for definitive info is for the top coat and whether its 5 - 1 -1 with lime or whether no lime and use plasiciser instead and also do i need waterproofer on top coat (top coat is being skimmed with plaster later) I have read that if using lime in top coat then dont use waterproofer. Am inclined to use waterproofer and plasticiser on both coats and no lime in which case presume use the plasticiser and waterproofer combined mixture.

Also can I leave scratchcoat for days/ weeks or is it more advantageous to put second coat on before scratch has fully dried ie same day.

dont think I'd want to do a whole wall thats for sure any advice much appreciated as doing this thursday...