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Old 09-12-2017, 02:20 AM   #1
ginahoy
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Join Date: Sep 2017
Posts: 3
designing 24 OC floor system specifically for tile

Hi, I'm new to this forum. I'm a building systems engineer. I design mechanical and (previously) automation systems for high performance homes.

I'm finishing up the structural drawings for my own new home in SE Arizona -- a ranch over finished basement. Before I hand off to my truss designer & structural engineer, I want to flesh out a preliminary spec for the floor system. I plan to have tile floors throughout the main level.

My open web floor trusses will have very low deflection (better than 1/720) due to relatively short spans and my requirement for 18" height to accommodate the duct system. The basement ceilings will be suspended grid (lay-in tiles) for permanent and easy access to all plumbing, wiring the duct systems

Here's the rub: I want the floor trusses to be 24" OC... not to save $ but to minimize interference for any future plumbing/electrical/HVAC mods. I'm willing to spend more than what I save over 16 OC to beef up the sub-floor, but I don't want to waste money out of ignorance. As you can imagine, I'm getting all sorts of advice from my contact universe (tile distributor, truss designer, GC, etc). I read SBC's guidance but it only addresses truss deflection. Of course, my concern is the unsupported span between 24-oc trusses, not truss deflection.

Searching through the forum, most of the threads on this topic deal with existing floor systems. But I did find a couple of comments that recommended 1-1/8" plywood subfloor with isolation membrane. I'd appreciate confirmation of that, or an alternative recommendation.

Also, there's a full bath on the main level and I'd perfer to avoid a transition in floor height (the entire main level will be tiled). Thoughts?
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