I just want to share with you guys my experience with a wooden garage floor and what I went through to get it ready to hold a small car.
Let me start with a picture of the shop before I started the work. (The only pic I could find was a "before and after" photo I did to get it cleaned up before replacing a Jeep 4.0 head gasket).
So as you can see, kinda, it's a plywood floor. There's a garage door with a concrete driveway leading up to it, and I've been parking my motorcycles and riding lawn mower in there but mostly I used it as a wood working shop, and storage. We bought the property two years ago and the house was a total fixer upper, every surface needed replaced. So the "work shop" was a very valuable space for operating a table saw, chop saw, router, glue-up table, etc.
The "garage" itself is a perplexing structure. There's a basement below it! Not a crawl space, but a full-height basement with concrete walls/foundation. There's windows, a brick chimney for wood-burning stoves (both upstairs and downstairs), insulation behind the drywall, and even a water pipe that has been capped off. So I think that the structure was built, maybe in the '50s or 60's, as an "in-law suite" or whatever. But someone "converted" it to a "garage" by adding a garage door and driveway, but did nothing to the floor structure... Or maybe it was always a dedicated woodworking shop and the garage door was to load and unload shop equipment.
Going down into the basement with a flashlight you can see some pretty obvious termite damage, and that there's been repairs in the past.
And there were several metal posts holding up very large crossbeams that looked like old rail road ties.
(the above photo is displaying incorrectly, it needs to be rotated 90 degree clockwise, not sure why that is)
The joists were 2x12 and spaced out, roughly, 24" apart. And they were not in good shape, but soon I learned that that was an understatement.
With the house remodel finally finished after two years, I really wanted to use the work shop as a garage for a project car (originally was going to be a '73 VW Beetle, but now I'm working on a '67 VW Type 3 Squareback. And using a Miata for an unconventional chassis swap).
I started the demolition.
I found two layers of 3/4" plywood, on top of loose (not nailed down) 3/4" boards, on top of the original (and half rotten) T&G flooring. But the worst part was the joists. ALL of the joists were completely rotten at where they rested in the notches of the concrete foundation under the garage door. So if a car had rolled in there it definitely would have fallen through the floor! I can't believe I was even riding motorcycles and lawn tractors over it. A few of the joists even had been hollowed out by termites the whole length of the boards. Even the new wood from a recent repair was eaten away by termites.
Per some "redneck engineering" advice on Reddit (I wish I had found this forum first), I was advised to tear out everything, double up on the joists such that they're now spaced 12" on center, with blocking in between the joists every two feet. Double up on the crossbeams and posts. Then three layers of 1/2" plywood on top, with staggered spacing and lots and lots of panel adhesive and fasteners. And use pressure treated 2x12s to avoid any future rot and termite damage. So that's exactly what I did. Unfortunately I'm struggling to find a picture of the completed floor structure, except for this snap I sent to Instagram...
And that only shows one of the three new crossbeams I installed. BTW, I'm only reinforcing the floor structure where a small, lightweight car will fit adjacent to the garage door. But that's also where all the termite damage was, and the rest of the floor looks solid.
It didn't help that I smashed my middle finger with my largest framing hammer swinging at full force (trying to hammer a joist into the notch in the concrete foundation, and the notch was too small). But it gets worse: I simultaneously yelped out in pain and jumped off the ladder, not looking at where I was landing my feet, which were outfitted in light-weight house shoes. If I had looked before jumping, I would have seen the old board with a large, rusty nail sticking straight up. Yeah, I think you can guess what happened. The nail didn't go totally through my foot, but it did puncture it by maybe a centimeter. I had to go get a tetanus shot and the blood drained from under my finger nail.
Have you ever seen a smashed finger this blue?
But I was able to hobble around and, with the help of a friend, get the job done. The floor is successfully holding a 2,000 pound car, which is about the limit that I would ask of it, even though it was "engineered" to hold closer to 4,000 pounds.
Sadly, I didn't have time to put some polyurethane down before the winter temps dropped and it was too cold. So when I'm welding and grinding, I lay down a welding blanket.
So there's my story, I hope you guys enjoyed it. If any body is interested in my project car, which is a '67 VW Type 3 that is chassis swapped with a '90 Miata, then please check out my YouTube channel: https://www.youtube.com/channel/UCVB-_yKtj4pRUpNI3xoe3-g. Thank you.