Let me tell you what, I really hope prepping the trailer and attaching the subfloor is the least exciting and least rewarding part of this building process! If I never have to drill another hole into steel again it will be too soon.
When we got our trailer, we found that the welds did not completely seal the steel flashing under the trailer to the trailer frame. Our manufacturer said the purpose of the gaps was to allow water to escape if it rained before we got our floor installed, however I was more concerned with water and bugs getting under the subfloor/into the insulation after the build was complete. After reaching out to others in the tiny house community via the Tiny House People Facebook group, I decided to use 100% silicone caulk and seal up the gaps in the flashing. Once this was dry it was time to install the insulation.
As I said in a previous post, we had our insulation delivered to us — which was supposed to be 2” rigid foam and foil-faced, a closed-cell insulation that was made with the least amount of chemicals we could find, and thus would have the least amount of off-gassing. When it was delivered, I began cutting it to fit the cavities in the trailer, only to realize at the end of the process that the insulation Home Depot delivered to us was 1” and I didn’t have enough to cover the entire floor. I’m not sure how this got by me when it was delivered, except to say that spacial awareness is not my forte and prior to this build I would not have been able to accurately approximate an inch. Anyways, my shortcomings aside, we had to call Home Depot to get a new shipment of the 2” insulation we had originally ordered. Much to our surprise, when it was delivered for the second time not only were there not enough sheets, but it was the wrong type of insulation altogether. Third time is the charm though, and we finally got the correct amount of the right type of insulation and were able to finally finish insulating our floor.
Once the insulation was done, my amazing dad came down help me install the plywood subfloor. We used 3/4” tongue and groove plywood, which had to be cut to size and placed correctly. This meant being mindful of which side the tongues and grooves were on, where the seams would land (as they are not supposed to line up or it would become a weak point in the structure) and maintaining a 1/8” gap between sheets to allow for expansion of the wood. Unsurprisingly, we ran into a few hiccups along the way. I quickly realized that with the length of the sheets of plywood and the placement of the trailer cross members, I would only have an attachment point for every other sheet. This meant removing the insulation I had just installed snuggly and cutting and strategically placing 2x4s to offer a nailing surface where I needed one. Once this was done, and the plywood was cut to fit, we began setting it in place!
To start, we made sure it was square to the trailer and then put a liberal amount of wood-to-metal construction adhesive on the trailer. We tacked the plywood into place with deck screws as we were trying to hurry to get as much of the floor on as we could before the rain came. My dad and I were able to get about half of the subfloor down in an afternoon, and had to cover up the rest of the trailer with tarps to protect the insulation from the elements.
After one more full day of work by myself, I managed to get the rest of the subfloor on…..and then went to work attaching it properly with wood-to-metal self tapping (not to be confused with self DRILLING) screws! Tish and I spent several hours drilling holes through the plywood and into metal trailer frame and then inserting a screw into each one. When we began, I was keeping count of the number of screws we used…..however as the number grew and the surface area covered still seemed small, I quickly became more frustrated by the count and decided it was best for all involved if I ignored the number of holes we had left to drill. To give you an idea, the boxes had about 40 screws in them and we went through at least 10 boxes.
With the last hole drilled and the last screw driven in, we had our subfloor! Our proud moment of accomplishment was quickly diminished, however, when I stood back and looked at our house, which still looked just like a flat bed trailer.