Self level compound pouring on fresh concrate - help!

marcz

Hi,
I need to level floor in garage - about 12 sqm. It will be lino or carpet tiles over so no need to be 100% level as for wood floor. Just need to smooth it out tbh.. Half of garage is in pretty big slope, it drops significantly (30-40mm) in one corner comparing to other end and also 20-30mm on sides.. I'm afraid to pour self level as it may just run away to sides and that corner which are mostly uneven, I know there is fibre reinforced up to 40mm slc but I will need too many bags to even this floor, and worse is I cant even predict how many buy to be safe? 10, 15?... To save on expensive slc / bags quantity needed, my mate suggest to pour sort of screed in those deep drops with sand cement mix (with some sbr polymers or even add fibres additives) and then apply thinner coat slc over full surface (after concreate cure). Is this good idea or is it asking for troubles? I found that poly reinforced concrete should be at least 15mm on bonded surface, but it will definitely goes thinner on edges... I think this way I should pour at least 15-20mm concreate mix on whole floor right? If, how long need to wait for concreate to cure before slc?
Thanks

FreeBear

You do realise that a garage floor is highly unlikely to have a DPM ?

Putting lino down will result in mold forming underneath, and carpet tiles will probably rot in time. So what is your planned use for this space ?

For the areas that require a lot of filling, I'd build it up with a cement/sand/fibre mix - If any admixture is needed, perhaps a bit of PVA. Finish off with https://www.screwfix.com/p/mapei-ultraplan-3240-self-levelling-compound-25kg/4959f - Tip. Use a notched trowel to spread it around, and don't overwork it once poured.

Ideally, you'd want to wait at least a week for the sand/cement to harden, but in this weather, you'd also want to cover it with hessian and damp down the surface regularly. Cement needs moisture to cure properly, and on hot days or with thin layers, it will dry out way too fast.

Furts

The garage slab is likely to have a dpm. Simply because pouring aconcrete slab straight onto hardcore is asking for trouble trying to get a decent finish and strength. But only OP knows for certain what they have.

FreeBear

Furts wrote: »

The garage slab is likely to have a dpm. Simply because pouring aconcrete slab straight onto hardcore is asking for trouble trying to get a decent finish and strength. But only OP knows for certain what they have.

Nope. Hardcore compacted. A layer of sand, again compacted. Pour in concrete, tamp down, and then float to required finish.

Kiran

Sand cement screed cures at 1mm per day so 30mm is 30 days etc. If you don't have a dpm below your slab you can get paint on one which will prevent the moisture coming up You can use your self leveler on this within hours rather than days. Do you have any insulation below the slab?

Furts

FreeBear wrote: »

Nope. Hardcore compacted. A layer of sand, again compacted. Pour in concrete, tamp down, and then float to required finish.

We will agree to disagree then. But don't turn up on my sites laying garage fllor slabs by your approach. Nobody needs confrontation. Everybody is just looking for a quiet life!

Aylesbury_Duck

Isn't a garage floor supposed to be slightly sloped? My last two houses have had garages and when I've had a clear-out and swept and washed the floor, the water runs towards the door and out.

FreeBear

Furts wrote: »

We will agree to disagree then. But don't turn up on my sites laying garage fllor slabs by your approach.

Its only a bit of concrete for parking a car on. It doesn't need insulation or a DPM (for most of the time). At the end of the day, to quote another thread, "Does anybody care?", its just a bit of cement.

armchaireconomist

I'd probably stick a sand/cement mix in the large drops to bulk them out, PVA the surface then go straight in (once dry) with about 5 bags of Everbuild latex self-level and see where you're at.


Remember self-level is not suitable for a top coat if you're doing anything particularly strenuous in there. You can bulk it out with some builders sand if needs be, max about sand 1:4 screed ratio, but be aware you have to "work" the mix a little harder.

marcz

Thanks for reply. I don't want mess with concrete / sand mix as it can ruin slc, it can crack if lay too thin, dry too fast etc.. I bought grinder with extractor, so will be taking down high spots and try to slightly even this floor so it dont have such dipping points. I dont know about insulation, dpm either.. I plan just to smooth out surface with slc after grinding, before installing carpet tiles, but what dpm before glue tiles on? It must be seriously expensive epoxy dpm?? Bitumen black one it isn't good idea for carpet tiles, is it? Other option will be underlay + carpet / that will also help with insulation slightly and can just lay damp proof poly sheet...
Also, slopy half and mostty low corner is on oposite site then doors, so no , it shouldn't be slope that way...

armchaireconomist

Grinding will work too, as long as you have a relatively flat surface to work from. Be sure to wet sweep the floor after grinding to get rid of dust, and a water/PVA mix between the slab and SLC will help it bond.


There's probably no insulation there, but you could drill a hole to check the depth if so. The DPM (if present) will likely be deeper than the level you're working at.


Do not bitumen the floor. If it's damp you're going to seal it in and likely push it towards the walls.


What are you planning on using it for?