Insulated sleeper floor joist system
With all the great insulation help I’ve received in just a short time, I thought I would ask some questions about another unique insulation situation I have.
An addition we have on our historic home was once a hobby flower shop that was added sometime in the 1940’s. It was built on a slab directly on-grade. Assuming no vapor barrier between grade and concrete and about 3.5″ or 4″ thick. At one point this was turned into a family room and we’ve since gutted and started over from scratch removing absolutely every shred of wood structure down to the brick.
The slab was pitched down to one corner approximately 5″ over the longest distance for water drainage. To counter this and for the logistics of the living space, we chose to go with a sleeper joist system to level everything out and provide an elevated floor. Once the slab was stripped, cleaned, small cracks sealed, and prepped, we put down a true 10 mil vapor barrier system (I have forgotten the brand of vapor barrier system we used) followed by the pressure treated floor joists. Sublooring, before the reclaimed oak flooring goes down will be 3/4″ Advantech glued and screwed.
Before subflooring goes down, we obviously want to put some type of insulation in. The plan has been to just use a ccSPF product between sleeper joists and right over the vapor barrier. Sounds like HFO blown ccSPF is a good choice. The vapor barrier is doing double duty and probably unnecessary, but was put in early during the building phase when we were going a different direction with the insulation.
1 – Is ccSPF the correct solution here? Minimum depth of the joists are 1.5″. Max being around 6.5″. Any level of insulation will help keep the floor warm during the winter.
2- Advantech sheathing seems to offer a built in moisture barrier with it’s engineered composition. Do we need to add another product between the insulated cavities and the subfloor sheathing, or just glue it, screw it, and forget it?
3- Should we be considering a different insulation option?
Side note about this slab: It is absolutely a dry slab. There has never been a moisture issues in the almost decade that it’s been exposed. I check regularly for any moisture issues.
This floor system has really been an odd construction project and very labor intensive to get it all level and contoured to the slab. Looking forward to covering it up and never thinking about it again.
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