Garden room floor

[Monkeysheed]

Hi all,

When I moved into my house I had a large shed built by the previous owner that was in a concrete base that he'd laid and leveled by hand. I've since taken the shed down and built a nice new garden room on the existing base. I'm looking to lay a floor consisting of something like 50mm kingspan insulation and with laminate floor on top. The problem I have is that, because the concrete floor was leveled by hand it is quite uneven. In places this is causing the insulation board to "see saw " and bend in various places. Self leveling compound is too expensive and over kill? Are there any other options?

I'm considering something like this...

5mm XPS Foam Wood & Laminate Flooring Underlay (9.79m²)

The XPS Foam Underlay is an insulation board manufactured of entirely recyclable materials. The underlay is produced from foamed polystyrene, a material that does not deteriorate. It is a lightweight underlay solution with high compression strength and provides excellent thermal and sound...

www.leaderfloors.co.uk

Which says it can even put some unevenness. If I used this I'd probably reduce the thickness of the kingspan.

Does anyone have any experience with this or have any other ideas?

 

[freddiemercurystwin]

You can use a thin layer of sand if you can get it level and manage not to disturb it when you lay the slabs on top, it even says as much in the Kingspan blurb somewhere, though the naysayers will say to use a leveling screed which to be fair is the ideal solution.