Render Sand

[Geo-B]

What is the choice of sand for rendering house external walls finishing with a dry dash? Sharp or Builders Washed sand. Looking through past posts it is unclear.

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The reason I asked this is I was advised to get Plasterers sand from the merchant but he changed the request on the sheet to WB Sand. Does he assume this to be the same? I have a renderer to apply my materials as this is what he does day in, day out. After reading some posts here it is not conclusive as to what I should have delivered. Washed building sand cracks easily because it is too soft & sharp sand cracks because it sets too hard!! This is what I'm reading from other posts. Can someone clear this up as he's due too get started soon. I stay in central Scotland if the weather has a bearing on the sand to be used.
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moderator

please note 10a

 

[bathjobby]

Sharp sand. As the name implies it has jagged sharp edges (as opposed to water washed round grains) so bonds much stronger. Shouldn't crack if you get the right mix (4 to 1'ish) and get it adhered to a good clean surface i.e. clear off all old remains and dust then 2 coats of 4 to 1 PVA to water mix to seal the area to be covered.

 

[Geo-B]

Thanks for replying bathjobby. Between posting this yesterday & now I found this: http://www.goldtrowel.org/rendering.asp

This is renderer training facility. Check out the mix. What do you think of this? Is it any wonder I'm getting confused. I just dont want it all falling off in a year or so.

 

[Freddie]

Sharp sand. As the name implies it has jagged sharp edges (as opposed to water washed round grains) so bonds much stronger. Shouldn't crack if you get the right mix (4 to 1'ish) and get it adhered to a good clean surface i.e. clear off all old remains and dust then 2 coats of 4 to 1 PVA to water mix to seal the area to be covered.

You do not pva the outside walls to apply render, it has to have a slurry/scud mix 1-1 or 2-1 splattered all over and allowed to dry for at least a week before applying render