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Plastering & Rendering

plastering disaster - finishing coat would not stick to scratch coat

Anonymous user 01/03/2024 - 2.50 PM

hello there I don't know where to start, I tried to put on a finishing coat on top of a scratch coat after about a week waiting for it to dry properly. Well instead to my horror as I tried to put on the finishing coat it just would not stick to the scratch coat but instead kept falling off I just could not figure out what was happening. Did I get the mix right? It was very dry despite me adding a lot of water at which point it just turned sloppy and would not stick to the hawk. I used 4:1 mix and tried to mix by hand measuring the materials in a bucket and then turning the mix over before I added the water. This has happened to me twice where something is going wrong with the mix it just turns out to be sloppy or do dry I cant get the cake mix like consistency that I see in college. Having said that they just give us ready mixed mortar which is sand and lime only. Firstly, please can some one explain to me how I can get that soft ice cream mix when I don't have a cement mixer as I am trying to mix by hand. Secondly why was the plaster not sticking to the wall and finally can you skim an outside wall which has just been rendered?

Are you a tradesperson and able to answer this question?

3 Answers

Rigsby Handyman

Rating: 5 out of 5

Southend On Sea

Hi, first thing what were you plastering on, such as con-block or thermolite, as this makes a difference as thermo blocks have more suction which will kill the mix very quickly if not had a good soaking before scratch coat then again before top coat. as far as mix no need to make it to strong as this just causes more problem such as being heavy hard to use and causes cracking, I would use 5/1 mix making sure it was full shovel of master crete or wallcrete, with small drop of febmix or washing up liquid not to muck and added to water not place in mixer or barrow this should give you a nice light soft mix easy to lay on and feather or derby of and nice for floating or rubbing up. hope this makes sense lot easier to do then write about, also if just going alone don't try laying too much on at once better one nice flat wall then whole rough house that you to embarrassed to say you did thanks and good luck from 44yrs of plastering col. Ps a good mix 4/1 and 1 hydrated lime nice soft mix.

Answered13 May 2014

Anonymous user

Did u pva the scratch? Paul

Answered4 June 2014

KM Plastering

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Newcastle Upon Tyne

did you pva your scratch coat get back to me about what you used for scratch coat etc

Answered2 August 2016