Buying Materials!

My mum’s been very helpful and she’s been to all the hardware stores with me so far.

For the floor I need:

– plywood (about 6 sheets)

– adhesive that works on wood and metal

– screws for metal

– an impact driver

For plywood I had to decide if I was going to use plywood or OSB (oriented strand board). I had to choose a thickness, and I had to consider weight. One of the hardware stores recommended using a 3/4″ tongue and groove OSB-like material that’s supposed to be better than normal OSB (which swells when it gets wet and doesn’t shrink back). But that would add an extra 150lbs. OSB might be the cheapest option, but it’s also heavier than plywood. Mum called a few different hardware stores and we decided to go with 5/8″ tongue and groove plywood at a middle price. Normally, yes, you use 3/4″ wood for your subfloor, and 1/2″ is definitely not enough, but 5/8″ is a compromise on weight and it’s rated to be able to span 16″-20″. If my crossmembers were 24″ OC I’d go with 3/4″ wood, but mine are close enough together. Plus I’m going to have a hardwood floor, which will add strength.

Note to self: plywood is too long for mini-vans. We got it home no problem though.

Note to self: plywood is too long for minivans. We got it home no problem though.

I started watching some of the tiny house how-to videos that I’ve bought or bookmarked, and came across the fact that plywood should go perpendicular to the supports, in this case the crossmembers. Hmm. Most tiny housers just lay their plywood parallel to the crossmembers because their trailer is about 8′ wide and the plywood is 8′ long. Then came the debate on which is worse: unsupported seams or ignoring the way the wood was manufactured to be oriented.

Testing both orientations.

Testing both orientations.

I decided to go with the unsupported seams only because they are tongue and groove. The joint is a lot stronger than plywood that’s just butted up against each other. Normally you would put wood between the crossmembers of your floor for the seams to land on, but after the insulation it’s too late for that. The instructional video I bought from Tiny House Build shows unsupported seams, and he has 20+ years of building experience. The seams seem plenty strong when you step on them, and orienting the boards so that the tongue and groove is down the middle saves me from trying to screw through the T&G into the very skinny crossmembers.

Another thing I had to think about was adhesive versus sill seal(er). Tumbleweed recommends using sill sealer, a thin piece of foam, over top of your crossmembers so you don’t have cold spots in your floor from the metal, but everyone else seems to opt for adhesive to prevent squeaks. Using both adhesive and the foam seems like it wouldn’t work very well. Your wood would only be bonded to the flimsy sill sealer, and with sliding the plywood in place, I think there’d be bunching and tears. I decided to go with adhesive. I bought one that adheres to wood and metal and has the longest drying time. I need to have time to get my plywood in place and secured. Screwing into metal won’t be quick.

I'll probably need more :P

I’ll probably need more 😛

Speaking of screws, my mum and I tried the local place but they only had one option. They told us about a specialty place that has tons of fasteners, so we drove up there, found the exact screws we wanted (for cheaper than the first place) and bought 400.

The one on the left is from the first store, and the one on the right is the kind I bought. It has little wings that bore through the wood so that the threads catch on the metal, not the wood. Both screws have a tip that’s meant to drill into metal and a larger head so that the plywood doesn’t pop off.

As for an impact driver, I’m looking at borrowing or buying one because my dad only has an impact wrench, not a driver. I’ve been told that a driver will make every job easier than your average drill. It’s too bad I didn’t know that when I bought my drill; I could’ve bought a set.


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"It takes as much energy to wish as it does to plan." - Eleanor Roosevelt

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