Concrete Slab - levelling query

[suttonsteve]

House extension floor slab approx 8m x 5m
My brickwork is up to DPC level and I am ready to have the concrete delivered for the floor slab. As the concrete will be finishing below the DPC level (to allow for insulation and screed) I am looking for advice on the best way to ensure the concrete is level.
I have marked the level all around the walls on the DPM but cant see a way of checking it will be level all over.
Do you think raking & tamping will allow the concrete to find its own level sufficiently for insulation on top?

 

[Norcon]

Do you think raking & tamping will allow the concrete to find its own level sufficiently for insulation on top?

Yes it should. Tamp it across the 5m span.

 

[noseall]

Do you think raking & tamping will allow the concrete to find its own level sufficiently for insulation on top?

Yes it will to a degree.

Don't forget that when you start slopping the concrete around the base that the 'fat' from the concrete will almost certainly eradicate any marks you have put on the dpm as well as pull it down out of shape in any case.

Use the (hopefully) level masonry and your eye as a guide as well as wieldy tamping board and a 1.2m level.

When we tamp the muck for an above-slab insulation fit we try and make sure that there are no excessive peaks after tamping. This can be done by drawing the levelling board (we use a featheredge) over the concrete or roughly trowelling it as you go.

 

[suttonsteve]

OK thanks both of you for your advice.

I have made a gauge that sits on top of the masonrey which will allow me to physically check the level when the markings become obscured and I will go with tamping for the middle section.

P.S. -Would the addition of fibres to the mix make it more difficult to work and level off?

 

[Norcon]

Would the addition of fibres to the mix make it more difficult to work and level off?

Slightly but not a lot. Fibers are a great addition to concrete. An extra £5 per cube here.

 

[suttonsteve]

Great, I'll go for fibres and get on with it, this has been bugging me for a while now, thankfully I found this site where I can ask the experts.

 

[handyman77]

What website is that then? Can you post a link?