RENDERING OUTSIDE WALLS PVA

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Do you need to pva bricks blocks etc before rendering outside walls thanks.
 
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No!! As long as the brickwork is sound, and there is a good enough key, just give it a wet down with a brush/hose, let it drain off a while, then put on your scratch coat while the brick/blockwork is still wet.
 
No!! As long as the brickwork is sound, and there is a good enough key, just give it a wet down with a brush/hose, let it drain off a while, then put on your scratch coat while the brick/blockwork is still wet.

What mix does the scratchcoat have to be?? Does it have to have any additives; say for waterproofing?? And what sort of consistancy are you needing??

Also how thick does the layer have to be?? I can plaster (not a pro) but not done any rendering. I would have to put battens up to act as a guide. Bit amatuer i'm afraid but if the end result is good im happy.
 
The mix for a scratch coat would be 4 to 1,,, plastering sand and cement. You would put a measured amount of waterproofer/plasticiser into the water. The thickness for the coat would be around 7 to 8mm,,, ish,, certainly no thinner,, but not much thicker either, otherwise the coat will be too heavy and slump/split. Consistency?? A fluffy, spreadable mix, with plenty of air in it.
 
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The mix for a scratch coat would be 4 to 1,,, plastering sand and cement. You would put a measured amount of waterproofer/plasticiser into the water. The thickness for the coat would be around 7 to 8mm,,, ish,, certainly no thinner,, but not much thicker either, otherwise the coat will be too heavy and slump/split. Consistency?? A fluffy, spreadable mix, with plenty of air in it.

Thanks for that dude, very helpful. Just before I go...my dad had a spread round his house years 25 ago to do the rendering outside and the final coat he mixed up had some sort of dye in it which gave a magnolia sort of shade when it dried. Whats is this stuff and is it available from general building merchants??? I didn't pay much attention in them days as I was a bit younger and more interesting stuff to do.
 
You can buy a "few" (not many), different coloured powdered dyes for mixing into mortar, to give it the colour of your choice. You have to be very careful when using it though. You have to be consistent with the amount you use in each batch. It has to be measured exactly, otherwise the colour will vary. You also have to measure the sand and cement too. Even when it's on the wall, if you flick a drop of water onto the wet render with a brush, while rubbing it up, that can lighten it up too. The true colour of the render wil show when it has completely dried out. You could save yourself a lot of work, by painting it the colour of your choice..
 

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