Sand and cement on cement board...

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Olliejim

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Hi Everyone,
Just looking for a bit of advice here.... I have a client who's house is covered in 1960's hanging tiles..she would like to remove the tiles and render but would also like insulation added externally...this is my plan..
Remove tiles, leaving felt and batton in place.
Fix 25mm celotex or similar.
Fix 12mm cement board, tape all joints.

Now, the tricky part... She is on a fairly tight budget, so monocouche and acrylic renders are out of the question. The desired finish is stone colour so my intention is to use a mix of yellow, holme, white cement and lime ( test panels to be made up to achieve desired mix). Is lime a bad idea? Maybe allowing moisture through and making joints visible?

My worry is how well this is going to adhere to cement board, should i use steel mesh/ fibre glass mesh? Also ive heard of rendering first coat onto a tacky Sbr slurry?
Any advice would be greatly appreciated.
 
You can ply instead of the cement boards, then eml wire over the ply. Scratch coat 4.1.1 sand,cement & lime, render MESH all the scratch coat, then smooth render top coat 6.1.1 use plastic beads
 
tottiman said:
You can ply instead of the cement boards, then eml wire over the ply. Scratch coat 4.1.1 sand,cement & lime, render MESH all the scratch coat, then smooth render top coat 6.1.1 use plastic beads
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If you apply mesh straight over the ply this will most probably crack.
Timber and sand & cement is not a good mix.
 
If rendering on ply your better to use roofing felt first (the textured rough shed roof type) overlapped then EML over that using screws and washers and put good dollop of SBR in your scratch coat. Ive used this method loads of times had no issues at all. Infact did a couple of dormers where im working today a few year ago so will put some pics up later (y)
 
tottiman said:
Eml over the ply first. Done dozens of them, we've never had any probbs with cracking.
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If doing it your way do you not even seal the ply first with say SBR ?? If not im very suprised you dont get cracks using only EML mate??
 
Defo don't fix the eml over the ply.
If you look at the correct spec it is ply,membrane,battern,membraine then rib lath
This is how we used to do it and it's to expament spec.
This is a dated method.
Just done a large job using external carrier board then a thin coat jub system which is guaranteed.
It's the best way for sure
 
When ever I have rendered over ply iv always done exactly as Bobby says and always 3 coated a pricking up coat a scratch and a top coat getting weaker as you go, did a out house at my parents house 6 years ago and not 1 crack in sight , good luck mate
 
Marshy said:
If rendering on ply your better to use roofing felt first (the textured rough shed roof type) overlapped then EML over that using screws and washers and put good dollop of SBR in your scratch coat. Ive used this method loads of times had no issues at all. Infact did a couple of dormers where im working today a few year ago so will put some pics up later (y)
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Same as u mate never had any problems and a lot cheaper to do
 
Marshy said:
If rendering on ply your better to use roofing felt first (the textured rough shed roof type) overlapped then EML over that using screws and washers and put good dollop of SBR in your scratch coat. Ive used this method loads of times had no issues at all. Infact did a couple of dormers where im working today a few year ago so will put some pics up later (y)
Click to expand...
Yeah we used to do it this way but put fibre in scratch. 20 years ago when first started with my old man. Would use a jub system now. But this Defo works [emoji106]
 
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