So its time to install the subfloor onto the custom made tiny house trailer. This process is very important as this is what connects the house to the trailer. We used nutserts and bolts to strengthen the connection. The sub floor is made up of polyurethane panels glued with plywood cut down from sheet. Damp proof course and polythene were used to protect the building envelope from moisture and reduce thermal conductivity. Custom made tongue and groove plywood flooring forms the finished floor surface and braces the subfloor.

This is not a common construction method but we are keen to experiment a little and see how it goes as it is tiny and we can afford to do this to some extent. The 100mm thick polyurethane with 25mm plywood at 600mm centers yields an R-value of 4.2m²K/W, using the Construction R-value Calculator. Minimum NZ building code R-value is 1.3²K/W. The method we have used for our floor yields R-values over three times higher than the current building code.

Using plywood helps the thermal transmission and rigidity compared to pine timber due to its density and glued laminated layers. This system includes bracing and insulation in one with no air gaps. These materials are lightweight and very strong which is ideal for a mobile tiny house.

Check out this video highlight reel of the process.