After removing the boards for the deck of my house, I then flashed the whole surface of the trailer with galvanized metal flashing. This will prevent moisture from getting into the insulation and floor framing and prevent mice or road debris from entering into the undercarriage. I made sure to overlap the seams and then used flashing adhesive to seal it all up. The sheets then were secured using staples and the vapor barrier was placed on top of that.
It’s worth noting my approach to moisture when it comes to my Tiny House. I have several layers of redundancy to prevent moisture from becoming and issue. First is the fact that the trailer is inherently off the ground, this means that there is a good air flow to dry out any moisture that does make its way under the house. I plan to have a gravel pad to facilitate better drainage under where the house is parked. From there I have the trailer decking which is pressure treated. I think it is very unlikely that much water will be able to get up underneath the trailer other than if I were to drive it down a road after/during a rain shower. From there I have a sealed layer of galvanized metal flashing. This will prevent any water from entering an because its galvanized, it is well adapt at handling it if it does. On top of that is a sheet of 6mil vapor barrier. On top of that is my floor framing and insulation. The floor framing is also treated and the foam is closed cell so it will not absorb any moisture. All in all I think moisture isn’t going to be a huge issue because of the air flow, but if it does get in, there are multiple layers to handle it.
First step was to cut a hole for the tiny house deck. The decking of the actual trailer is treated lumber, to cut the hole I used a sawzall to make the cuts.
Then I attached galvanized flashing to the deck, being sure to overlap the seams and seal them with flashing adhesive.
Then I added a 6mil vapor barrier.
Finally all my floor framing (covered in depth in another post) is all treated lumber.