Ive read a little about those I-beam frames, it was interesting but they're not something I can use to replace the original joists. Heck, I cant even use joist hangers for the new ones I cut. I have to notch out a true 2x8 and then cross nail them to the sill.
As for underlayment I looked all the options and Im gonna go with ditra, seems like a lot less work.
just an FYI, I got joists 16 inch o.c. 3/4 inch beaver barf and that floor is solid AND level!
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Guardian of the honey and nuts
Let's assume I'm right, it'll save time.