when do I need to have the underfloor insulation ready?

[CalvinHobbes]

So complete newbie and just trying to get the timeline in my head for when I need the underfloor insulation. It's block build and we will have underfloor heating. So presumably the walls and roof go on first but still should I buy it sooner and try somewhere to store it.

 

[JohnMo]

Mine went in before any walls and then used concrete as screed. I found that way easier than the normal, build the house and fight around the walls. Nice blank canvas to work with.

[JohnMo]