Foam for under aluminum floor

[BigTerp]

Looking for some 1-1/4" foam to lay under my aluminum floor. Going to need about 10' x 4' total. I want to make sure I'm getting the right stuff. Is this what I'm looking for?

https://www.lowes.com/pd_304089-210-304089.0_0__?productId=3122445&Ntt=foam+board&pl=1&currentURL=%3FNtt%3Dfoam%2Bboard&facetInfo=

https://www.homedepot.com/p/Owens-Corning-Foamular-InsulPink-R-7-5-1-1-2-in-x-2-ft-x-8-ft-Furring-Lap-Foam-43WD/100320293

Just by looking online, I don't see anything in 1-1/4" (the height of my ribs). Would I be better off going with 1" or 1-1/2"? Thinking the 1" might allow some flex in my floor and not provide a whole lot of extra support. But I'm also thinking the 1-1/2" is going to cause problems when I go to rivet my floor to the ribs and my angle supports.

 

[Quackrstackr]

You could always use 3/4 + 1/2 to get your 1 1/4 that you need.

 

[BigTerp]

Thanks. That makes sense. Say I can't even find two different sizes to equal the 1-1/4" that I need. Would I be better off going 1/4" short or a 1/4" long?

 

[Quackrstackr]

I would say 1/4" long for support unless your floor is thick or your stringers are close together. You could make it full support that way if you had the tools to U notch one side of it out for your stringers.

 

[BigTerp]

Thanks.

It looks like Lowes has the sizes I need, 1/2" and 3/4". Is this the "blue" foam that I'm looking for?

https://www.lowes.com/pd_304091-210-304091.0_0__?productId=3122449&Ntt=foam+board&pl=1&currentURL=%3FNtt%3Dfoam%2Bboard&facetInfo=

 

[Colbyt]

Blue or pink the color doesn't matter. Extruded closed cell no water absorption those are the key things. A month ago Home Cheapo was a bit less than Lowes with the same size selection.

 

[lckstckn2smknbrls]

I'm secure enough in my masculinity to use the pink foam.