Render mix - Confused HELP please!

22 Feb 2006
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United Kingdom
Please guys help me! I have read so much about plasticisers, waterproofers, in the scratch coat, not in the scratch coat but in the top coat, hydrated lime or not.... HELP. Lime is very expensive, is it necessary 1:1 cement. Can I do without it all together?

Ok scratch coat 4 - sharp/plasterers sand to 1 cement
top coat 5 ditto 1 ditto

What thickness should each coat be? 7/8mm?

Please help with the lime, plasticiser, water proofer.

Thanks guys in advance, Barry
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1: if you are using sand and cement then the lime you will be using will be hydrated, thats cheap as chips

2: scratch coat thickness depends on the trueness of the wall you are putting it on. (always use an integral waterproofer in your scratch coat) i don't care what anyone else says. don't add lime to the scratch coat and 4:1 is perfect

3: before the scratch coat check wall/walls for cracks or mortar movement, mesh these with stainless eml

4: 5:1:1 sand/lime/op and good plasticiser, don't get it too fluffy. NEVER put a stronger mix on top of a weaker mix

the waterproofer will 1: stop mortar joints ghosting through plus will give you time to edge up nice an flat and float at a reasonable pace. don't forget drip beads over windows and above dpc.

hope this helps

ps get any organic material off first i.e. moss/algae/ivy etc and eml over any timber (forgot to mention that) plus if you have a straight mortar joint? put back to back stop beads for expansion/contraction

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