Monday, January 24, 2011

Foundation Sandwich is hours away from Flooring!

With the trailer stabilized and 56 bolts attaching treated 2x6 timbers we were now ready to commit to attaching the "engineered panels" we made to each other and to the trailer. All but one were kept in the full 4x8 plywood size. The CDX Plywood was treated and we laid down Tyvek as a barrier for the outside edge of the foundation sandwich which will eventually have sheathing and siding on top of it. We marked a point zero at the rear left hand corner and squared and aligned each piece attaching them to each of the bolted 2x6 timbers. We also then attached each of the 4x8 section together using the heavy construction adhesive and over 25-3 inch deck screws. Once the flooring is complete and we attach the walls we will run bolts every 2.5 feet through the wall plate, foundation sandwich and trailer to tie it all into a single unit. Here is the trailer as we set the first panel at point zero.
We worked our way up the trailer a panel at a time making sure the entire package was square. Then we worked on the one panel space that needed modification.

I had the trailer width built to 98 inches to see if I could gain a slight width advantage. But after a few sessions of deliberation about overall width, over hang on the roof, width of walls, and transportation restrictions I relented and went with a 96 inch build out. It made this process a piece of cake as each sheet of plywood fit perfectly. I have an inch of trailer width on each of the panel and we will run metal sheeting as a sill so water won't collect there. As I look at this picture it looks like a lot of space but add a half inch of plywood and 5/16 inch siding and the width of the folded metal sheeting and it should not be an issue.
I choose to go with R-Max rigid board. The two inch boards have an R value of 12.9 and the 1 inch have an R value of 5.6. On a 2x4 on end I have 3 and a half inches that I need to fill. I have seen this done a variety of ways through my searches. I decided I wanted the most R value that I could get in a 2x4 pattern. On the Mini Mobile Cottage blog, Jeff stated very clearly they were not as warm as they expected to be by using the all white foam board, so I went with the R-Max to end up with an R rating of  18.5. I believe I will spend around $1100.00 on insulation but I think it is worth it knowing I expect to live in either Portland or Seattle areas. I also come from living year round on a sailboat that has a robust quarter inch of fiberglass for insulation. R 18.5 sounds toasty warm to me.

The insulation was really easy to work with (we will see how it is doing the roof area) and we cut it right to width and then trimmed as necessary to fit. I had several cans of foam and didn't even look at them as the fit was so tight. After putting in the two inch boards we came back and put in another inch board and only pressed it to the edge of the 2x4 so the air gap was in the middle of the insulation, well for the most part. I will start next weekend by putting on the remaining CDX plywood. That will be screwed and glued per my standard practice and we believe it this a rock solid single unit that is intimately tied to the metal of the trailer. Next weekend we start the flooring!


  1. Hey there! I saw your future home on Tiny House Blog - it is going to be interesting following you on your journey. We have a small home - 10 x 32. It can be pulled with a truck, but it is not as 'mobile' as some trailers. We have a son, and a business, so we are pretty stationary for the moment. Our plan is to use our tiny home to save money, and move overseas at some point. Later we may rent it out....We LOVE our lifestyle. Here is my home:

    May it go well for you!

  2. I just wanted to stop by and say welcome to the "Tiny House" world. If you ever need anything, feel free to hit us up over at We are building a 30' x 8' ourselves.


  3. Came over after reading Tiny House Blog. So glad to catch you near the beginning of your build. I'll be reading along. Happy building!

  4. Hey Bryce! It's Meredith! It's so cool to see what you're doing. Contact me?