How long to wait between layers of self levelling screed?

[NoSpam]

I need to build-up an area of floor using self-levelling screed, how long do I need to wait between layers and is it necessary to PVA each time?

Dave

[Stuart Noble]

It isn't necessary to pva at all, and it's best laid in one go. You can fill holes etc with ordinary mortar first

[Merryterry]

Trade users usually use primer (PVA) first to get a bond to the initial substrate. Usually no need to build up in layers. If you do, no need to prime between layers. Proprietory brands can be trafficked in an hour or so dependant on Temp/Humidity etc

[NoSpam]

Thanks, and to Stuart.

[The Natural Philosopher]

Its more a question of preventing the stuff drying before it sets..you get a huge 'suck' onto dry screed.

Usually no need to build up in layers. If you do,

[Lobster]

Agree with the PVA advice... I once used it without priming the substrate with disastrous results - next time I used PVA and all was fine.

I do think you need to use layers though, as per manufacturer's instructions (ie, if you're filling a deep 'hole') however, if you're needing more than about two layers I'd be using a sand cement screed first to fill up the bulk of the space, before finishing with a single layer of self-levelling compound.

David

[Ed]

replying to NoSpam, Ed wrote: I?ve had the same issue on a large floor which was a long way out of level (40) bags out of level! I did it in three pours but used SBR bond between the layers to control suction.