Kiln-dried sand for render top-coat??

[Czar]

I've now scratch coated a block garden using plastering sand. This sand was very stoney, but has gone on the wall quite nicely.

Is there any glaring reason why I couldn't use a finer sand (kiln-dried?) for the top coat to give it a finer finish?

Any pro's and Con's?

Any thoughts much appreciated...

 

[roy c]

You might have used "concreting sand" ,it should of been "sharp" sand. You can use this sand for scratch and float coat dont use kilm dried or building sand for rendering....

 

[trowelmonkey1]

i've had plenty of plastering sand too lately from three different merchants that's had stones in up to 10mm!! Very poor!!

Plastering sand needs to be well graded so that you need less water to mix it to a good workability but shouldn't be any more than about 4mm really so how lumps like this size i've been finding has been ending up in there i'll never know.

This also makes me concerned about how well washed it is if this is the level of quality control they're applying to their product manufacturing/bagging process.

Really bad form IMO as bad sand can cause real problems.

 

[peaps2]

This also makes me concerned about how well washed it is if this is the level of quality control they're applying to their product manufacturing/bagging process.

Really bad form IMO as bad sand can cause real problems.

It's an issue that comes up if we have to use a different supply.

 

[Czar]

You might have used "concreting sand" ,it should of been "sharp" sand. You can use this sand for scratch and float coat dont use kilm dried or building sand for rendering....

It was actually Wickes bagged 'Plastering Sand'. About twice the price of sharp or building sand too...

Another point, the wall is saturated from days of endless rain. There's a window in the weather tomorrow and I'm hoping to get the float coat on. Am I ok top coating a wall that will no doubt still be quite sodden from all the rain we've had? I know it should be dampened down prior to rendering anyway, but it's had far more than that!

 

[trowelmonkey1]

all the problems i've had has been pre-bagged stuff too.

only way to answer your question is to say 'give it a go' if it slumps then it's too wet.

 

[roy c]

You shouldn't really render on a rain soaked wall as there will be no suction at all and you need a little suction, so I would let it dry out a little if you can. If you do spread it and it's a misty, moisty day lay it on and dont play with it and see if it picks up, it might be a few hours before you can screed it, net alone put a float on it. You might be lucky....