Floor Box - Day 10-13

DAY 10 (Saturday, January 17) (0.5 hr): We flipped the floor box! YEAH! My sister and parents, my uncle Chuck, and two friends from high school, Sarah and Becca, helped out. Thank you!!! 

I'm afraid I didn't take any pictures during the procedure ("Okay, everybody hold it... hooold it... just a sec... now, smile... got it! Okay, one more") and somehow forgot to take one afterward. Huh... I was pretty foggy that day. I was actually afraid I was coming down with the flu that's going around--my head felt like it was made of clay and I spent the rest of the day half-vegetative watching Netflix--but it passed. So. All good!

Here's a nice picture of the floor when I finally got around to photographing it in all its right-side-up glory (plus the Tyvek that I added on Day 12).

It took seven adults' worth of muscle power and a ten-foot length of PVC pipe to roll the floor off and on the trailer. When we got it off, we laid it on a pair of 2x4s on the driveway, flipped it, picked it up and rolled it back. Getting it back on the trailer was tricky, because our objective was to set it down inside the trailer--not back on the 2x4s that had been elevating it before. Lesson 17: It would have been a fantastic idea to slip some nylon webbing under the floor and lower it down that way. Instead, we did it the finger-pinching way. Ah well. It all worked out in the end and miraculously, no one was injured.

First three bays lined with Tyvek!

DAY 11 (Sunday, January 18) (1.25 hrs): I started filling the bays with Tyvek house wrap. I owe this idea to Kate from Naj Haus--I hope she was right about it!

The way I justify this (admittedly difficult and time-consuming) step is as follows. I'm looking at the floor box as analogous to a framed wall assembly: the painted 3/8" plywood undercarriage corresponds to the siding/cladding on the exterior of the wall. Directly under that is a water-resistive, vapor-permeable house wrap--i.e. Tyvek, the most common brand name--that protects the structural elements of the wall from any moisture that might get past the siding. In this case, if the undercarriage gets soaked, that moisture won't transfer through to the insulation... though unfortunately, it can transfer to the joists. Normally, a wall would then have structural sheathing, like OSB or plywood, which we're skipping in the floor box. Next comes the framing lumber with insulation installed between the sticks, then the interior wall sheathing, which corresponds to the 3/4" plywood subfloor. For the time being, I'll leave the floor at that; later, when time and budget allow, I'll probably lay some sort of flooring down over the subfloor.

[An aside on vapor barriers: Tyvek is not a vapor barrier. It's an air and water barrier that allows water vapor through, to allow drying, just in case any water somehow gets inside. But when I get around to installing flooring, I may use a vapor barrier between the plywood subfloor and the flooring. Now, from what I've learned online, vapor barriers are rather controversial. I'm not enough of a building scientist (that is, I'm not a building scientist) to weigh in on the controversy and make decisions for myself; I'll probably just do whatever the building codes say to do. For my climate--Marine Zone 4--the International Residential Code (IRC, the rulebook for building houses in the United States) requires the installation of a totally or mostly vapor-impermeable layer (i.e. Class I or Class II vapor retarder) on the interior side of walls. My floor is more like a wall than a normal house's floor, since it's exposed to the elements, so that requirement seems to apply here. Of course, tiny houses on wheels are outside the jurisdiction of the residential building codes, but I'll try to follow the code when possible... just in case. After all, it is a house, even though it's on wheels!]

Tyvek corners cut and folded to create a 3D fit.

So, back to the Tyvek plan. The plan is to fit the Tyvek pieces as tightly as possible inside each bay by cutting diagonal slits in the corners of the material so they'll fit the three-dimensional space. The Tyvek should come part of the way up the 2x6 joists, but after the edges and seams are taped, the tops of the joists should still be clear, so I can glue the plywood subfloor directly to the joists. 

This job combines all the worst bits about wrapping gifts, adds wind and cold, and subtracts the part where it's a gift. Ugh.

On Day 11, I got three pieces in place and stapled, and one of them taped. The stapler failed to shoot out a staple about 75% of the time; very frustrating. And I realized that Lesson 18: a utility knife is not a good Tyvek cutting tool if there's no broad work area and soft (plywood or cardboard) surface to cut on. Scissors are way better. Would've been way better, if I'd had some handy...

But, kind of good thing it was so frustrating, because I got tired of working on it by myself and came inside the house in time to watch the local professional sportsball team sports their way to (improbably) winning a spot in the upcoming SuperSports Bowl, or whatever. So, cool. (I've never been a Seahawks fan, or, like, a fan of any sports team... but when in Rome, eh?)

DAY 12 (Monday, January 19) (1.25 hrs): Mom, Dad, Ellen, and I all trooped down to Seattle to put Ellen on her flight back to school in California. That afternoon, I came back to the floor box with Mom and a couple pairs of scissors, and we finished cutting and fitting Tyvek for the bays. Luckily, we only taped one more piece in place, since I need to get behind the Tyvek to do Day 13's job...

DAY 13 (Tuesday, January 20) (2.25 hrs): Dad and I bought 16 carriage bolts, each 5.5" long and 5/8" thick, plus a washer and a hex nut for each one. The trailer has 16 bolt holes pre-drilled in the sides of the trailer bed, on about 24" centers. First, we centered the floor box in the trailer bed so that the principal joists and rails line up to where the edges of the subfloor plywood will be. Then we started drilling holes and installing bolts.

Before we started bolting the floor in, we realized that we would need shims, or spacers, between the trailer frame and the floor box wherever the bolts attach, so that tightening the
 bolt would not pull the frame out of alignment. We wanted something made of a relatively insulating material--not metal. We looked for nylon washers at the hardware store, to no avail. Then we considered maybe cutting our PVC [Edit: it's actually ABS] pipe into 1/2" disks and using those. But we ended up choosing a free, easy, better approach: we took a few pieces of 1/4" and 3/8" plywood scraps, plus a big roll of green, foamy stuff (floor underlayment? Looked like a giant roll of Sill Seal), from Grandpa's garage, cut each material into square pieces that
would fit flush with the floor box, and wedged stacks of them between the frame and floor at each bolt hole.

Why is that a better approach? The problem with using a single-piece spacer of a predetermined thickness (e.g. slices of PVC pipe) was that the gap between trailer and floor is not equal everywhere. Try as we might, it just wasn't. Using our chosen method, we could adapt the thickness of the spacer by using different bits of plywood--two 1/4" pieces here, a 1/4" plus a 3/8" there. Then, the foam was a slightly squishy and insulating layer that helped everything fit and stay in place. We drilled and bolted right through the whole thing.

Front end where the floor box sticks out of the trailer frame.

You might wonder why I'm standing on the floor box while Dad drills a bolt hole in the top picture, above. It wasn't just for the sake of an artsy angle. Both ends of the floor box stick above the edge of the trailer frame, for some reason! Boo! The back end, fortunately, was fixable by standing on it, hence the photo. We bolted it in place and all is more or less well. The front end stuck out more and only moved a little when I stood on it. We'll need to plane down or something, because it just doesn't fit. Boooooo! 

Lesson 19: Always have a fully charged spare drill/screwdriver battery on hand.

Lesson 20: Keep the drill straight and level! Luckily, we didn't have any bolt holes swerve out of alignment with the pre-drilled holes. Even the ones I drilled. Whew.

Lesson 21: If your drill bit is the same diameter as the bolt, you'll have to hammer the bolt through the hole. It'll be okay.

And, of course, Lesson 22: Plan to have your plans come out imperfectly. See: using variable-thickness spacers because the frame was not totally square and straight and plumb and whatever.