Today I completed the insulation and installed the plywood subfloor.

I trimmed off the excess spray foam and then just before I was about to drill the holes and bolt down the trailer, I remembered that I was going to put a sill gasket down in-between the metal trailer frame and wooden floor frame.

I’m glad I remembered just in time!


I propped up the trailer frame and started to work on using the ‘foam board’ adhesive (stuff that doesn’t melt foam). It wasn’t going on very well, so I checked the packaging and it stated to not apply under 15 degrees C.

As it was 9 in the morning, the sun hadn’t yet hit, so it was certainly a lot more challenging and time consuming than it should’ve been.

It got way easier as the morning warmed up.

Attaching the frame to the Trailer

After going back and forth in my mind, I finally decided to attach the trailer with two coach bolts on every alternate joist, a few feet in from either side and 2 on each side, each one midway between the wheel wells and the ends of the trailer. (I will also use 6 Simpson Strong tie HDU 5’s on the sides near the corners and wheel wells later on)

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After reading so much on other tiny house building blogs about the nightmares people have had drilling through steel and having to replace a number of drill bits, I was not looking forward to it.

Despite all the concerns of others, it went very well. True enough, I needed to apply a lot of pressure, but as I was only drilling through 3.5” of wood followed by about an 1/8” of steel, it wasn’t too bad.

The $10 drill bit lasted for all 18 holes, way quicker (and more fun) than a usual round of 18 holes!

I left the nuts off, just incase, but mainly because that can be saved for a wet weather day. Whilst it’s sunny, I’m gonna be on top of the trailer!

Attaching the Plywood Subfloor

Now, I’m not 100% happy with my work here, but I’m not too upset either.

I’d already laid out plywood for the base, so my initial plan was to copy the same format as you saw in a previous post. This time however, I was installing tongue and groove plywood.

Tongue and groove plywood has a tongue on one long edge and a groove on the other long edge. The short edges are straight and normal. The tongue fits into the groove, which holds them solid (good for floors) but also causes them to loose a half inch in span as you join them together.

Remembering that I have an awkward sized trailer at 100” x 241.5” and that I was well aware that the plywood should lay perpendicular to the joists, I continued ahead with a layout that would attempt to save me a sheet of plywood.

Unfortunately it didn’t.

I simply had a small brain fart for a moment and went with ta layout similar to this.

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The reason I did this was that after laying them out in-front of me in both configurations, it seemed to workout better this way, and more solid due to their being no blocking in the centre of the floor. So away I went.

Half way in, it crossed my mind that I should’ve followed ‘protocol’ and laid them perpendicular.

In hind-site though, I would have laid them perpendicular, but cut them off short so that they lined up with the blocking underneath. It would’ve wasted more material that way and cost more money, but it would’ve been the ‘better’ way to go. (as you’ll have noticed, lots of different ways to do things, and lots of opinions out there).

Having said that, the floor is solid and I don’t foresee any issues. I still can’t fathom if it would’ve been better the other way or not. I’m not going to loose any sleep over it.

Aside from this confusion, the fitting went well.

I decided to use treated deck screws to hold the panels down good. When fitting them, make sure you don’t go screw right up to the edge of the panel until you’ve attached the next piece. This way it’ll make it easier for you to bang the tongue and groove together.

Looks and feel great.

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What’s Next?

So with the floor completed, it’s time to go UP!

A milestone in the build for sure. I was going to pay someone to do the floor for me, but decided against the $1800 CAD quote.

I’m sure later on as I look into the budget and such, we can see how much it cost in materials and therefore calculate how much my 6 days labor was worth!

For now though, it’s onto the walls!