Do I need to use levelling compound

[Stupida]

We had a new floor poured recently in a garden building and the intention was to....

• Pour and spread a layer of levelling compound
• Then lay four inch PIR (over black plastic sheet)
• Then float a wooden floor on top of the PIR

I laid down a sheet of PIR loosely around the floor with the spirit level riding on the PIR and it shows perfectly level everywhere, even if I bridge the level across two sheets.

So do I actually need the levelling compound step?

 

[Tigercubrider]

Imho - no
When we did something similar, we used rockwool over plastic and then chipboard flooring. The rockwool gave enough for the floor to be fine

We did add dollops of mortar to the original garage floor , using a spirit level to connect the high spots and filling in gaps but not much. I.e. The floor was rough as a badger's arse and we made it roughly better.