Laying a traditional sand and cement screed advice required please

[george75]

Is insulation needed (Polystyrene) around the edges

 

[Bonni]

The insulation around the edge is normally there just on exterior walls, those walls that face outside for cold bridging purposes. I normally add SBR to the mix to stop crumbling and dusting.

 

[bobasd]

typicly the edge insulation should come up level with the FFL.

the way i go about this is to lay 25mm+ blinding sandover hardcore.
then a membrane that laps up the walls about 50mm to 75mm above FFL benchmark. tape the membrane up.

then lay insulation with edging insulation reaching above the FFL - it can be cut back later, and tape insulation joins.
then pour concrete to height neeeded for finished floor height- allowing for finished flooring cover eg. tiles.

if possible we dont use topping screeds . they waste time and mats and can delay slab drying.
the top of the slab is lightly plished for laying final cover.

as a diyer you want to leave your slab as long as possible before screedin or you may blow the screed.sometimes this happens down the road when the tile or laminates been down a bit.

 

[noseall]

as a diyer you want to leave your slab as long as possible before screedin

The screed will bond better to a partially dry slab than it will to a bone dry slab.

sometimes this happens down the road when the tile or laminates been down a bit.

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Cement based products will bond ok to a partially dry slab but it may slow the curing process. Laminates or any timber products however, does rely on a bone dry substrate.

 

[^woody^]

You dont need any perimeter insulation or expansion room, but if the walls are solid and don't have any insulation in them, then you may want to include 5 or 10mm of foam to pervent any condensation. Bear in mind the skirting width though, as you dont want any edge insualtion showing, and may need a firm base for carpet grippers

Make sure the screed is reallyreally dry. The slab will need to be dampened to ensure a firmm bond.

 

[george75]

You dont need any perimeter insulation or expansion room, but if the walls are solid and don't have any insulation in them, then you may want to include 5 or 10mm of foam to pervent any condensation. Bear in mind the skirting width though, as you dont want any edge insualtion showing, and may need a firm base for carpet grippers
Make sure the screed is reallyreally dry. The slab will need to be dampened to ensure a firmm bond.

Thanks for the helpful advice