insulation question

[learning]

We are building a post and beam building with outside dimensions of 26' X 36'(one 6' bay, two 12' bays and another 6'bay) which will be open to the public. The handicap bathroom needs to be in the first 6' bay which has an inside dimension of 60" from the stem wall to the first post. We need a 60" wheelchair turning radius. We can set the wall opposite the stem wall toward the middle of the post, but not too far for due to other space needs. We are installing radiant heat in a floating slab which is not yet poured. Currently, the footing and poured concrete stem wall are back filled. There is 2" rigid foundation insulation along the inside of the stem wall up to the top of the stem wall. There will be 2" of the same insulation beneath the slab. I have read about cutting this at a 45 degree angle in order to bring the slab close to the stem wall. Here is what I need help with. The stem wall will be 8" above the slab. We are planning to put foam insulation in the studded walls which rest on top of the stem wall. The person who put the rigid insulation assumed that we would have the insulation on the side of the slab continue to the top of the stem wall and could build a shelf and cover it with baseboard. My framer says that I will lose about 4" to the 2" insulation plus framing and baseboard. At least in the area of the handicap bathroom, I don't want to lose the floor space. However, if the insulation is cut at the height of the slab and my foam insulation is blown between the framing sitting on top of the stem wall, I have 8" of uninsulated stem wall around the perimeter. My thought is to dig out stem wall on the outside and put rigid insulation there, but I fear that in ne CT that we will need to go to the frost line. If we just insulate the outside of the stem wall a foot or 2 down, I can see the cold migrating up the stem wall and passing through to the baseboard. What are your thoughts about insulating the 8" above the slab? If we insulate on the outside, should it go to the frost line? If we don't cut the rigid insulation at the slab, the slab will sit 2" away from the stem wall. Is this acceptable?

Another question: should there be a thermal break between the stem wall of the building and a slab under a lean to porch? How is this break bridged for a wheelchair? This slab will extend to a sidewalk to handicap parking spot.

Thanks, learning

 

[Wingnut65]

Welcome to GJ, learning. Lots of questions...

First, for the accessible bathroom, there are a lot of requirements besides just the 60" turning radius. The radius must not be overlapped by an in-swinging door, but may overlap the clearances for the toilet and lavatory. Then there are the grab bar requirements for the toilet that can control the room dimensions. It would be best to have a local architect who is familiar with your local codes and regs for some guidance.

For the porch slab at the stem wall, there should be some form of expansion to allow movement as the slab expands and contracts with weather changes. The gap at the door can be covered with an aluminum threshold.

Now the insulation at the 8" stem wall will need some input from GJers familiar with construction in your climate. Yes, there should be insulation to keep the cold out. It may be only needed for the 8-12" to get below the slab since if you would have it on the inside of the wall, it would stop at the top of the slab. If its only for 8", I don't know if 2" of rigid insulation board glued to the block and GWB glued to the insulation may be an alternative.

Hope this gives some guidance on your project. BTW, what will the shop be used for. FYI, you will have more traffic to this thread if this is posted in the General Discussion instead of just here at the Intro page... Good Luck

 

[learning]

Thanks for the help. The building will be an office.