Uneven concrete subfloor

[Ouch77]

I've got a poured concrete subfloor in my extension which has a height variation of 20mm over a distance of 3m in some spots. there's a layer of PIR insulation to go down before UFH pipes and screed. It's about 27sqm area all in, so that makes for 0.25 to 0.5 cubic metres to fill (depending on the average height variation). It's new concrete (poured last summer) and has a decent DPM underneath it.

I'd like to even out this variation, as I want the screed thickness as even as possible, and I obviously dont want any wobbly PIR panels under it. I don't mind bringing the level up a little as the current measurements are giving me quite a thick top screed layer to get the final floor height I want.

How best should I go about this? lots of bags of SLC? what flavour? Water based seems favoured in the FAQ - any brands or products to look out for?

 

[Bonni]

You have three options, either build up the low areas with self leveller, or grind down the high areas, or a bit of both.

You can hire a concrete grinder, I got one from a local hire firm. Farmers often use them to put rough grooves on the concrete to reduce cows slipping.