It's all about the layering here in Nova Scotia.
We have our 24ft, galvanized custom trailer - that's exciting.
The first job is to get the floor (our foundation) insulated.
Please keep in mind we are building for Canadian winters, so we take our insulation and cold protection seriously!
The cross pieces are 3" 'I' beams. These 'I' beams give us a lip on each side and on this lip we attach puck board, caulked in place with exterior caulk/adhesive. This is all held down by strips of milled hemlock that are wedged under the upper lip of the 'I' beam. Puck board is used here to line the inside of hockey rinks and is just about as indestructible as can be. It wont rust, wont break in the cold, and is impervious to bugs or critters trying to get in from below. This makes it perfect for the underside of the trailer. With this all in place there are no exposed spaces on the underside.
After we install the puck board we work our way up, first a layer of 1.5" SM ridged foam with all the joints and edges sealed with expansion foam. On top of that another layer of 1.5" foam making sure all the joints on the lower level are overlapped. This brings us flush with the top of our 'I' beam. Finally a last layer of 1" ridged foam that sits within the space of our floor system. This last layer is hugely important as it gives us a thermal break between the steel of the trailer and out eventual floor.
On top of all the insulation we have a 3/4" ply layer, which is the underfloor for our finished floor which will be installed later. In this tiny shelter the floor is going to be locally grown and milled Ash.
All this gives us a floor with a R-value of 20, plus it gives us multiple layers for draft protection, vapor barrier, and thermal break from the steel trailer. This system would be overkill if you were building in a warmer climate, but is worth the extra time and money for our winters!
Last step - leveling the trailer using our new handy laser level!
Next step is framing the walls, and on the snowy days working in the shop on the curved roof trusses.