Hi - I have a 1 storey extension to the side of my house - the previous owners had got as far as getting the scratch coat on but never got as far as getting the top coat done.
The extension is a big old building - originally an old bakery - going back to the early 1900's so is solid brick construction.
The scratch coat looks pretty solid and is waterproof as we have been in the house for about 5 years and no water ingress.
I am now feeling brave having built up my DIY skills and want to apply a cement top coat. The wall has been beaded and is ready to work on.
The only problem that I can see is that a small wooden window lintel was rendered over and the scratch coat has cracked and is coming away - there appears to be no eml on this.
My questions are:
1 - Do I need to wash the scratch coat down or treat it with a fungicide? - the surface is dry and clean with nothing growing on it.
2 - How much sand would I need to give a 6mm topcoat (60 SQM)?
3 - I have read that the top coat needs to be made with a 5 : 1 plastering sand : cement ratio - should I use these ratios; also do I need to use an admixture? (I have some Febmix) should I also incorporate some lime to prevent cracking?
4 - How much water should I use in the cement mixer/what kind of consistency do I need the muck to be?
5 - I was planning to rip up some 6 mm plywood to make battens and screw them to the wall to ensure a level finish when I use the float. However the wall length is 19 metres and its height is 3 metres - realistically how much wall could I cover before the mix becomes unworkable?
6 - For the wooden lintel can I just use eml (how do plasterers get that nice curved finish above the window?)?
7 - Do I need to cover the render with polythene whilst it is drying?
I plan to practise on a section of my garden wall first but I am hoping that I can get a reasonable finish using the float and sponge.
Any tips/help will be greatfully received!
Cheers
Ghekoman
The extension is a big old building - originally an old bakery - going back to the early 1900's so is solid brick construction.
The scratch coat looks pretty solid and is waterproof as we have been in the house for about 5 years and no water ingress.
I am now feeling brave having built up my DIY skills and want to apply a cement top coat. The wall has been beaded and is ready to work on.
The only problem that I can see is that a small wooden window lintel was rendered over and the scratch coat has cracked and is coming away - there appears to be no eml on this.
My questions are:
1 - Do I need to wash the scratch coat down or treat it with a fungicide? - the surface is dry and clean with nothing growing on it.
2 - How much sand would I need to give a 6mm topcoat (60 SQM)?
3 - I have read that the top coat needs to be made with a 5 : 1 plastering sand : cement ratio - should I use these ratios; also do I need to use an admixture? (I have some Febmix) should I also incorporate some lime to prevent cracking?
4 - How much water should I use in the cement mixer/what kind of consistency do I need the muck to be?
5 - I was planning to rip up some 6 mm plywood to make battens and screw them to the wall to ensure a level finish when I use the float. However the wall length is 19 metres and its height is 3 metres - realistically how much wall could I cover before the mix becomes unworkable?
6 - For the wooden lintel can I just use eml (how do plasterers get that nice curved finish above the window?)?
7 - Do I need to cover the render with polythene whilst it is drying?
I plan to practise on a section of my garden wall first but I am hoping that I can get a reasonable finish using the float and sponge.
Any tips/help will be greatfully received!
Cheers
Ghekoman
