Render problem

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Ashleyscoob

Ashleyscoob

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Had a conservatory to outside render dwarf walls and a apex above windows that was ply dwarf walls block.

Eml on ply mixed fibres in scratch with waterproofer on block work bedded mesh in scratch as well

topped it and it all started to crack Just as we had cleaned up so put it down to being a hot day scraped top coat off and cleaned all the scratch lines out thinking will top again when bit cooler as scratch coat was fine
just rendered it today not a hot day no sun on it dampened scratch before topping went lovely finished at 12 went back at 6 and it's all crazy cracked couple areas had lifted rest is not hollow thinking can I put a thin coat render over to sort out with a primer first or will it all need meshing first with a base coat if so what is the best base coat to go on the render
thinking sand has got to be the problem with this but it's is plastering sand which have used before
 
Hey up,

I had similar problem on patching job when my local merchant changed where they got silver sand,
I put it down to sand being really fine so try just normal building,
or if you've got a labourer like mine keep eye on him to make sure the stuff isn't turning too long in mixer or he's putting in too much cement.
 
4-1-1 scratch 5-1-1 top coat we did use the mega mixer drill to mix as not worth getting mixer out for a little amount but have used a drill before with no problems
 
To be fair top coat was at least 12mm suction was not great as the top coat on scratched ply took 2 hours from being put on till sponged up must be sand but it's not soft sand
 
Dunno if i'm right or wrong but i give my scratch coat a watery coat of external PVA if i've got ant concerns,
Any one else try this or am i just wasting glue.
 
Ashleyscoob said:
To be fair top coat was at least 12mm suction was not great as the top coat on scratched ply took 2 hours from being put on till sponged up must be sand but it's not soft sand
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Difficult to say for sure without being there but it does smack of sand with to high a silt content.
Also 12mm is a little over thick for the top coat, 6-10mm would be better. Personally with rubbed up work I aim for 8mm.
EML straight onto ply is a bad idea and EML onto battens should have a prick-up coat first before the scratch.
 
Ashleyscoob said:
What's a pricking up coat before scratch coat ?
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Thats a coat of render applied to make the eml more ridgid. when thats cured you would apply your scratch coat. Like andy mentioned you should have a gap behind the EML so the render can wrap round it self(if that makes sense) but the ply would restrict that happening
 
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Just never heard it called a pricking up coat before but would have done that if needed but over ply the scratch would grip to elm ok or not what mesh would you advise over ply . The scratch coat is fine even on ply. Would the jub thin coat render sort it out
 
Ashleyscoob said:
Just never heard it called a pricking up coat before but would have done that if needed but over ply the scratch would grip to elm ok or not what mesh would you advise over ply . The scratch coat is fine even on ply. Would the jub thin coat render sort it out
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EML is always 3 coat work marra. not sure about the jub gear but someone else will be able to comment on that
 
When you went over the ply did you use anything like a breathable roofing felt between the ply and wire?
 
where was the sand from ? please dont say bq looking at there rendering sand yesterday look the same as sand for laying bricks.
 
henry said:
where was the sand from ? please dont say bq looking at there rendering sand yesterday look the same as sand for laying bricks.
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Sand was from pit close to me it looked fine not to fine have used it before to render a bungalow last year ,have seen b&qs and would never use it
 
Ashleyscoob said:
Just never heard it called a pricking up coat before but would have done that if needed but over ply the scratch would grip to elm ok or not what mesh would you advise over ply . The scratch coat is fine even on ply. Would the jub thin coat render sort it out
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i find it better to use rib lath then eml and batterns. prickup and scratchcoat in sharpe sand. sharpe sand mixed 50 50 with plastering sand for finish. we never use white cement to risky, to expensive, they can decorate it what ever colour they want with a quality external paint. you have to learn how to lead customers by the nose!
 
Been to have a look at render today now dry and it's not blown just cracked so think will hpx with mesh over top 4 mm then prime and jub thin coat never used thin coat before any tips on when to rub trowel over it
 
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