Floor Box - Day 20 - FLOOR BOX RECAP

(2.5 hrs)

The floor box and subfloor are FINISHED! We screwed and glued the last three pieces of subfloor plywood today.

The next step is to add the walls. Since I'm using SIPs--structural insulated panels, a prefabricated wall panel system--the wall installation is kind of out of my hands for the moment. I contacted the local SIP manufacturer a couple of weeks ago and they promptly replied promising to get back to me with a price quote, but I have not heard from them since. Once I get the quote and get some answers to my design/building questions (e.g. What kind of splines do I need? Is there anything I need to do to "hurricane"- and "earthquake"-proof a SIP structure? Do I need a double top plate?), I will place my order. But then it could take a month or more for them to fabricate my panels and deliver them... I really don't know at this point.

So I wait.


But anyway, now it's time for a photographic recap of the floor building process! I've taken the liberty of idealizing the order of some of the steps, so take this is the order in which I should have done everything I did:

1. Built the floor box frame (joist system) from 2x6 lumber attached with joist hangers and nails. Placing the joists on 24" centers would have been the standard procedure, but I chose to place them over the trailer ribs for extra support, resulting in uneven spacing. Somewhat of an inconvenience and probably resulted in an overbuilt floor (average spacing closer to 16" than 24"), but hopefully no big deal. (Result: feels rock-solid!)

I also chose to place joists where they could support every plywood edge, with a minimum of plywood cutting and wastage. Having all plywood edges supported by a joist: good idea.





2.  Glued and screwed on an undercarriage made from 3/8" CDX plywood. This will protect the bottom of the house from pests, road debris, moisture, and other baddies.

 3. Caulked all gaps and penetrations in the undercarriage.












4. Primed and painted the undercarriage with water-based exterior paint. The paint will help seal the plywood against weather.
















 5. Laboriously ensured the paint would dry in drizzly, 35-45ºF, Pacific Northwest winter weather, using a giant tarp, a variety of kludges to keep it from touching the tacky paint, a fan, and a small electric heater (that sometimes worked).













 6. Jacked the floor up and out of the trailer bed and, with help (7 people--thank you Chuck, Becca, Sarah, Mom, Dad, and Ellen!), flipped it over and placed it back in the trailer, undercarriage side down.

7. Shimmed the floor box in place, drilled through the side rails of the floor box at each pre-drilled bolt hole in the trailer, and bolted the floor box to the trailer using 16 carriage bolts, each 5/8" in diameter and 5.5" long.









8. Filled the gap between trailer and floor box with R-6.6/inch aerosol spray foam insulation, which works perfectly well at 45ºF (at least if the can is at room temperature to begin with).
















9. Discovered bits of the floor frame that protruded above the trailer frame and planed them down with a rented electric hand planer.















 10. Lined each bay with a water-resistive barrier (Tyvek house wrap) and taped all the seams with house wrap tape. This serves as a second line of defense against any moisture intruding into the floor box from beneath. It's the same idea as when you build a house: the three outer layers are paint, siding, and house wrap, all serving to protect the inner pieces of the house's walls from moisture. I have paint, an undercarriage, and house wrap. The house wrap and tape will also keep out any drafts of air, should air somehow enter through the undercarriage.








11. Snugly filled each bay with R-23 rock wool insulation. Filled any gaps with aerosol spray foam insulation.











12. Roughed in 2" ABS drain lines for the shower and kitchen sink, the only two plumbed items in my house (no flush toilet, bathroom sink, clothes washer, dishwasher, etc.).

13. Covered the trailer width extensions with Sill Seal as a thermal and air barrier.
















14. Glued and screwed 3/4" CDX plywood to the floor box, covering it and the trailer width extensions.
















TOTAL TIME: 20 days, 40.25 hrs (generally with two people working together)