Shite sand

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Birdythespread

Birdythespread

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Hi lads, has anyone in the herts beds bucks region had problems with rendering sand ? Been doing this since 85 and I've never had any probs up till recently, rendering hair line cracking the day after, all jobs scratched, then two coat, ruled, floated then sponged, walk away from the job perfect next day map of England , use multi-cem cement, render guard gold W/P, even lime, but the sand seems **** locally regardless of various merchants , at a loss now HELP:RpS_biggrin:
 
Hi mate , not had much to do with multi cem , only like using blue circle opc , apart from thickness of top coat and two coat on eml , i cant help sorry
 
@Birdythespread like Church I only use OPC for rendering.
When you say the sand is shite what exactly is it you don't like about it?
Have you checked the silt content of the sand?
Are you using fibres in your mix?
 
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I do not use multicem only opc. Used the same source for plastering sand for the last 25 years but every now and then it is course and 'dead'. I use 20% soft sand when this happens. Rest of mix is either Feb Rendamix or Febmix and sometimes lime.

Top coat in summer may be 6:1:1 but in the colder months 5:1:1/2.

i never put more than 1 lime to less than 6 sand. Had it stronger in the past but hairline cracks.
 
id agree but only small hairlines maybe 20mm never road map , i think its more to do with water content per gauge
 
I did a 6:1:1 job without Feb and that cracked all over. The mix used a lot more water than with Feb.

But in this case the OP used multicem and plasticised w/p. Too much plasticer for my liking.
 
i think that some branded cements are stronger than others , some are heavy in additives like multi cem . , i like to stick with opc and adjust the mix and ratios per job in hand
 
we have had the same before I find a lot of so called plastering sand comes up to fine so we always mix sharp and a small amount of building sand seems to bind it together nice . we always use the opc blue circle paper bags seems the mastercrete and others have got to many plastiscers in them
 
I've always used Leighton sharp, which was fantastic, but the pit has gone, the sand almost seems as if the goodness has been washed out of it, it's almost like sugar, really hard to use a few spreads around here are refusing to render because of it, not used fibres, do they not come through when you rub up ? Cheers for the help mate ,
 
And just reading down ill definitely try going back to opc, all the merchants sell or push the multi-cem / mastercrete etc in the poly bags, maybe it's too much with the render guard gold w/proof.
 
Yes the fibres come through to the top. Ok if you are going to give the render a coating.
 
church said:
i think that some branded cements are stronger than others , some are heavy in additives like multi cem . , i like to stick with opc and adjust the mix and ratios per job in hand
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i've often wondered about that - are all OP cements the same strength or not? I usually use blue circle, even though it's french owned. Sometimes castle or rugby cement, that's about all we get up here, but I never use different cements on the same job just in case there's a difference.
 
The local merchants to me all sell blue circle/larfarge opc. The blue circle rapid give a different colour.
 
id say thats quite a weak mix for opc general rule here is 4:1 scratch 4.5-1 float the rest, lime plaza etc is tailored to personal preference. we never tend to get to many problems with that mix we do alot of opc work in Guernsey
 
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