Insulating basement - foam walls or pour floor first?

Question

Basement is unfinished, 100 year old house. Basement floor is dirt and various crumbling sections of old concrete. Walls are rubble and cement and above grade brick.

I'm planning on leveling the floor with tamped gravel, putting down foam board, radiant tubing and then pouring concrete and then probably tile. Walls will be foamed with closed cell foam.

Foam company said to do the floor first, but I think you'd want to foam first and pour the concrete to the wall edge and the foam will provide expansion for the floor.

But I really don't know and maybe it doesn't matter.

Any ideas?

Ok, considering the comments below, here's my order of operations: This would create a fully thermal-sealed basement:

1. Lay down gravel in the basement to level it. Tamp that down, mechanically.
2. Lay down vapor barrier and then Foam board on the gravel basement floor, probably 3 inch.
3. FOAM THE WALLS - connects all the way down to foam board.
4. Wall mount the manifolds for radiant
5. Lay down the radiant tube (wire mesh attached or template board attached)
6. Pour concrete floor
7. Install the boiler(s)

Answer 1

Unless you plan on allowing your basement slab to experience extreme temperature swings, expansion isn't really an issue.

It's common to create thermal breaks where beneficial to energy efficiency, but that could simply be a strip of 3/4" foam around the bottom. You don't say how thick your wall insulation will be, but that's probably too much of a gap for the slab.

Answer 2

I like the idea of 3/4" foam board around the perimeter of the slab. This will provide the thermal break. Unless the walls are in really good shape you might consider mortaring up the rubble walls. You could Gunite them as well. This could save major head aches in the future. PCL