Not quite a SIP question, but has anyone used Nailbase as floor insulation?  I want a little insulation between a first and second floor to (hopefully) improve the efficiency of hydronic radiant heat.  My idea would be to use nailbase with 5/8 OSB glued/screwed to the existing subfloor.  I would need to route the OSB (and a little insulation) for 1/2 pex tubing.

Anyone used it?  SIPs are available as floor panels and a nailbase is half a SIP, so are there any specs on using SIPs as floor panels?  The specs on nailbase (and probably also therefore SIPs) tend to quote psi, typically 10-20 psi, which is ridiculously more than the 40 psf that a floor needs, but fails to consider point loads.  I'd hate to have an 800lb piano on it's four little wheels permanently embedded in the floor.    (But the piano problem would be the same if I had 5/8 OSB on 16" joists which is - just - permissible).

Thanks,

Jim

Jim;

I would be afraid of the EPS crushing, the piano problem would be different as you have positve bearing and attachment at every joist with no "soft" give.

If the finish flooring is a very stiff hardwood (like oak), and wide-plank (5-6" or more) you can probably get away with it, but not with laminates or 2" goods of any species. The old subfloor & joists will still flex some to help distribute the pressure. 200lbs resting on a rigid 6" round pad is still only 7psi- 6" of flooring plank + 5/8" of OSB nailbase will be evenb better, and likely to keep you within the specs of even low-density EPS even with the wheels parked close to the flooring seam. With 2" flooring parking the wheels on the t&g seam would likely impart enough twist to the flooring to create localized compression in the EPS but it would probably distribute well enough with the wheels centered on it. (Under stuff like concrete slabs the weight distribution is even better.)

All excellent points, Chris!

I hadn't really thought about it much, but while OSB can work OK as subflooring if it can dry to the other side or drain, laminated with EPS it's a water trap (unless it's pitched to drain, like say, up on a roof or on a vertical wall.) With the vivid image provided by your 20-20 hindsight I can see how in places like kitchens & bathrooms it OSB SIP floors could be a disaster waiting to happen. (Thanks!)