After removing the dark laminate, we notice a bit of sag in front of the fridge. So we decided to strip the older plywood subfloor and see what condition the metal floor was in. Other than some grime and screw holes, the floor was in good condition! The prior owners had ground down all the rivets to make the subfloor flat. It may have succeeded in making the floor flat but it was also contributing to it's current condition quite spongy.
Eighty percent of the rivets had been ground down enough that a simple tap was all took to prep the hole. The remaining 20 percent needed a bit more elbow grease. The quickest way to do this is to use a rivet to push the existing rivet out. Put the round end of the rivet on the center of the sheared rivet body and tap with a hammer. With luck, you'll have a nice clean slate to work with.
The subfloor was not without value. By serving as templates, they allowed me to bypass the trim, test fit, and repeat method of carpentry. I tapped a nail in each existing screw hole to mark the new plywood. To minimize the chance of split wood, I took the time to drill guide holes on each nail mark. Tedious work but it paid off.
I used upside-down rivets to align the floor with the existing holes. The screws are flat heads. Normally one can torque them into the wood until they are flush. In this case I'm working with sheet metal which has already held a screw. Without enough metal surrounding the threads, the screw would strip the hole before the desired depth is achieved. The solution is to use a large drill bit and countersink the screws. Another tedious step, but well worth it.
A note about rivets: I had two lengths of 3/8 rivets. Both work just fine, but the longer rivets mean double the number of times you have to squeeze the rivet pliers. Sure, laugh now, but after 100+ rivets, it adds up!
Day end tally:
- Existing floor removed
- New floor shapes cut
- New rivets in metal floor
- First panel in
- BONUS - Rich the electrician stopped by and gave us some electrical help. One rejoined yellow wire in place and now the electrical system works!
Larger pics below.