Floor Box - Day 4

(3.75 hrs of "real" work)

Ahhh--I am now sitting and relaxing with a bottle of hard cider and a cup of tea after the longest and most visibly productive work day so far. Today Mom and I picked up the insulation from Lowe's, and Dad and I installed the undercarriage. Good day!

FYI: Four packages (~160 square feet) of 5 1/2" Roxul insulation exactly fill a 2008 Toyota Sienna minivan from the middle seats back. Now you know!

Also: I discovered why we ran out of lumber and joist hangers yesterday. I had actually mistaken the number of joists needed in my drawn plans, not realizing that one of the spans in my drawing was greater than 24". When actually building the floor, I saw that the gap was too wide and corrected it with an additional joist, thereby adding two pieces for which I hadn't planned.

To build the undercarriage, we measured, cut, and installed sheets of 3/8" CDX plywood as we went. Each piece of plywood completely covers whatever outside rail its edge(s) falls on, and halfway covers the center rail and joists that its other edges fall on. This way every edge of plywood can be supported, and the undercarriage is flush with the floor box frame. Measuring and cutting as we went meant that we could adjust for slight inconsistencies, which Lesson 10: are basically inevitable.

Shown: gluing and screwing, 6" edge/8" in the field fastener schedule

Every piece of plywood was glued and screwed to every joist and rail it touched. We used 1.5" deck screws, and we placed them every 6" around the edge of each sheet and every 8" in the field, that is, in the middle of the sheet (in construction terminology, that was our fastener schedule). Before screwing the sheets, we laid down a 1/4" bead (that is, line) of Liquid Nails construction adhesive along all the surfaces the sheet would touch--enough to squish out and have to be cleaned up before it glued our upside-down subfloor to the trailer!

We used a Sharpie to mark the trailer where the centers of the joists were, then drew a line across the plywood sheets so we would know where to screw in the field. This is the kind of good idea that is obvious if you have a little experience, but maybe not necessarily obvious if you're a total deer-in-headlights newbie. (Maybe that should be Lesson 11, along with the tip to buy a couple of carpentry pencils and use them whenever you need to mark up wood/plywood for measurements and such.)

I decided to stagger the seams of the undercarriage plywood. Since all the seams are supported by joists and rails anyway, I'm not sure that staggering them was necessary or helpful; but I had enough plywood for all the pieces required, so I did it. Maybe it will mean my undercarriage is more structurally sound. Maybe not. But it can't hurt, right?

Lesson 12: Impact drivers are the best! I get tired after a few screws using a regular battery-operated screwdriver, but I did my fair share of screws with my new impact driver and felt fresh as a daisy throughout. The caulking gun for the Liquid Nails, however, was another story... we got the cheap-o $10 gun for our big 28-oz tubes of Liquid Nails, and Lesson 13: that might have been a mistake. My forearms are going to be sore tomorrow, for sure.

Tomorrow I'm going to fill in the gaps and cracks in/between the plywood sheets with caulk (that gun again...) and then paint the undercarriage with a couple coats of pale green exterior paint left over from when we painted our house (if it's still usable!).