Self levelling compound - the right depth?

31 Jan 2013
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United Kingdom
Planning on laying self levelling compound down as a screed base for insulation/ufh/tiles. Planning on using Wickes high performance SLC, will prime with PVA 50/50 x 2, so hopefully got most bases covered! My query is how I accurately get the SLC to a set depth as I have to base everything round the toilet / wastepipe. The subfloors concrete and I've flattened n filled but still has about up to 5mm variations - I'd want to have a min depth of 4mm SLC (up to 9mm in the deep spots). Someone suggested screws levelled to a set depth, but would that cause weakeness in the SLC? Try n draw a level round the battened border??
Thanks in advance and for all the other very helpful topics I've found on the way
DIYer novice Dan
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Actually having measured a bit more accurately there are changes of about 10mm in places - was a bit of a nightmare breaking it up as its a very old extension with three layers of tiles all on top of each other and now discovered three different levels of concrete/flagstone/hardcore running across! Been filling in the wholes with sharp sand cement mix 3:1, should I keep doing that or use a couple of layers of SLC instead? One to fill in the depressed portions the second to give a smooth top layer??
Thanks again!
What I do is fill any deep holes with Ardex rapid repair a45.
Then prime and screed any unlevel sections.
Then do a top coat screed to the whole room.
Thanks dazlight
Room primed and ready to go with the first levelling screed in the morning!
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personally i wouldnt use the wickes stuff.

A pro would never use. If you have not purchased yet then try and find a flooring wholesale outlet and get a proper flooring brand like - Mapei, Fball, Ardex.

Also you shouldnt prime a floor and then leave. You should apply compounds within approx 8 hours.

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