Levelling a slab

[Dibs-h]

The slab in my workshop pools water in a few places - so I want to level this before putting the DPM down and then the kingspan, along with the 3"x2" bearers (infill with more kingspan) and finally the 1" play floor.

A sand and cement mix (dry'ish) sprang to mind. Any suggestions otherwise? What mix? Use plasticiser? Building sand or sharp sand?

I suppose the max depth is likely to be around 1" max. As the DPM will be going down - I suppose it cracking subsequently won't be an issue - it's just so there aren't any voids and full load transference from the floor down to the slab.

 

[Ed68]

The best product would be self leveling floor compound you buy it in tubs and just pour it over the floor or into the hollows if your only doing spot repairs. You'll still have to prime the floor as per the instructions.

Its good stuff you can feather it from 1 inch to 0 and it shouldn't break up at the edges like normal sand and cement screeds can.

The other option is 4to1 building sand/cement mixed with render plasticiser till a creamy consistency, paint PVA 1to1 with water onto the areas to be filled wait till its tacky and fill the hollows in. Another good additive is SBR instead of plasticiser but it costs more and you would also prime the floor with that as well.

You can't feather semi dry cement screeds to 0" they will break up.

Hope this helps

 

[MikeG.]

Dibs,

Ed68 is right.....Self-Levelling Compound is your answer.

Mike

 

[Triggaaar]

Ed68 is right.....Self-Levelling Compound is your answer.

Most self-levelling compound is supposed to be used above DPM, not below, because it expands/contracts when it gets damp, but I don't suppose that's important in your case - in which case I'd recommend Wickes deep leveller, which is buy 3 get 1 free (works out £8.80 a bag). If you have a large area to fill it can cost a fair bit though.

 

[Dibs-h]

Ed68 is right.....Self-Levelling Compound is your answer.

Most self-levelling compound is supposed to be used above DPM, not below, because it expands/contracts when it gets damp, but I don't suppose that's important in your case - in which case I'd recommend Wickes deep leveller, which is buy 3 get 1 free (works out £8.80 a bag). If you have a large area to fill it can cost a fair bit though.

Cheers Trig - I'd spotted the same one last night.

 

[Mr Ed]

If you're worried about moisture affecting it you can use 5 star grout instead.

Ed

 

[eoinsgaff]

If using self leveling compound note the following:

If possible try to calc what you will need over all as you will have only shot at it. Don't panic, its not going to go off very quickly but you need to move things along promptly. Have everything ready. It all has to go on the floor together so theres no chance for a 'trial mix' to see how it looks.

Wet the floor below first so it doesn't draw all the moisture from the compound too quickly, making it set/cure too fast and crack.

Make a little screed to tamp the mix, encouraging it to find its own uniform level.

Just a few points I've learnt from experience...

Eoin

 

[OLD]

Why not just level the 3x2"s with solid packing strip dpc and grout it will cut right down on labour and materials and then use that tar paint synthaproof? on the slab etc.

 

[markwuzere]

a cheap alternative to self leveling compound, but only any good when going to be covered ,as in your situation is to mix cement with water and a small drop of pva and trowell that into the dips, over time it will crack and does require a little more work but is cheaper and as your putting another floor over it it will be fine. I've done the same in a few situations and never had a problem. Just to add i would never use this method when leveling a screed for a finish floor only for sub-floors etc

 

[Dibs-h]

Wickes were doing buy 3 get 1 free for bags of their Deep Leveling compound. 8 Bags later and the floor is almost spot on.