Floor Box - Day 19

(3.5 hrs)

Today we installed two more pieces of subfloor plywood (it's halfway done now), roughed in the sink and shower drain lines, and finished the floor insulation.

It sounds so easy when I condense it down to one sentence! The full story after the jump...

Separation anxietyyy

 The first thing I did today was actually discover a spot where the undercarriage is separating from the joist. Oh no!

But I don't know what, if anything, can be done about it. We can't screw it back in from beneath because of the trailer rib there.

Lesson 26: If you build an undercarriage like mine, keep your weight off it. It's really not intended to support weight. I wasn't very careful about this--much easier to kneel in the bay than balance on the joists...--and I'm thinking that's what caused the separation. I should have laid some plywood or boards down and put my weight on those while I worked in the bays.

I hope there aren't any problems down the line caused by this little bungle. The only thing I can think of is that there might be more air circulation than intended. I'll check next time I'm at the site whether any of the edges of plywood are coming loose... that would be a real problem, since it would be a direct path for air and water to enter the floor box. Boo.

Anyway. The big excitement today was... drain lines! 

The floor was overbuilt anyway, right...?

I've decided on a 32" x 32" shower (a departure from my original plan of a 24" x 32" RV tub, which would have been shoddy quality and too small), which only comes with a central drain 16" from each side. With the shower right in the back left corner, this landed the drain precisely on top of a joist--to be precise, the joist that's coming loose from the undercarriage. The shower installation instructions call for a 5" square hole, so we cut a hole into the joist 5" across and about 3" deep--deep enough to accommodate a tight 90º elbow pipe fixture, with some headroom.

That elbow has two female ends. The upper end will connect to a 2" ABS plastic pipe that leads up to the shower drain. We won't install that until we install the shower. The lower end we connected to another 90º elbow that had one male and one female end. We attached an 8" length of 2" pipe to the female end of that and stuck it out the bottom of the floor through a 2 1/2" hole cut with a circle saw.

2" ABS plastic drain pipe and fittings

 Rigid plastic plumbing pipes come in three flavors: polyvinyl chloride (PVC), chlorinated polyvinyl chloride (CPVC), and acrylonitrile butadiene styrene (ABS). PVC and CPVC are the white or beige ones. We're using ABS pipes, which are black. To connect ABS pieces together, we used a multi-purpose solvent cement for PVC/CPVC/ABS, which we wiped on the surfaces that would be in contact, then immediately stuck the pipes together and held them in the position we wanted.

Lesson 27: Solvent cement acts fast and is not reversible, so carefully mark the final position you want and make sure you land on the mark within a couple seconds of sticking the pipes together! Solvent cement also emits lots of really noxious fumes, so make sure the ventilation is good. And make sure you close the little can of cement as soon as possible, because it will continue to fumigate your workspace as long as it's open, and it will harden up quickly when exposed to air.

Roughed-in drain, strapped in position

We needed to secure the drain in place, so we screwed and nailed a piece of scrap 2x6 to the joist next to the drain. Then we added some shims--pieces of scrap plywood--so that we could press the drain against something and have it be in the correct position to receive the shower drain pipe later. Then, with Dad firmly holding the drain in position, I attached the drain to the 2x6 and joist with a couple pieces of strapping. Lesson 28: This is a two-person job. Some jobs just are. Have a helper. I tried for a long time to hold the pipe and attach the strapping alone while Dad worked on the other end of the trailer with the subfloor, but finally I gave up and asked him to give me a hand... and then boom, it was done, easy as pie.

Later, when I'm installing the shower and know the exact final position that the drain needs to take, I'll fill in around it with Great Stuff. The rigid-curing foam will lock it into the specific position I need. Right now, with just the strapping holding it in place, there is a little bit of wiggle, which is good; according to the installation manual, there is up to 1/2" of tolerance (variability) in the exact position of the drain in the shower pan. I hope the drain is exactly in the center of the shower, but we might be able to swing it if it's not.

Next up was the kitchen sink drain, which was so, so, so much simpler than the shower drain. The kitchen sink will be elevated above the floor, obviously, so the position of the drain doesn't need to precisely match the position of the sink; we can reroute the drain under the sink on its way to the floor if we're off by a few (or more) inches. I was able to position it based on convenience rather than necessity, so I put it right next to an existing joist.

As before, I cut a hole in the undercarriage and re-taped the Tyvek around it. Then I cut an 18" length of pipe, positioned it so that it would stick up above the subfloor somewhat, and (with Dad holding in place) secured it with two pieces of strapping. I wanted it to stick above the subfloor so it will be easy to access to connect it to the rest of the drain and sink. Like the shower drain, I will foam the pipe in place later.

The parts of the pipes that stick out underneath the trailer are placeholders. Later, we will cut them shorter and connect them to each other with a T fitting, with the third branch of the T being the pipe that directs all the gray water away from the house and into a gray water reed bed/wetland, exterior storage tank, or--least desirably--the sewer.

After both drains were strapped in place, I put insulation around them and then we called it a day.

Filling in the insulation

Done!