I Hurt

The last couple days have been devoted to the installation of a sheet metal underbelly on my trailer.  Think:  hours on your back in a one and a half foot tall space holding a crunch while applying enough upward force to drill through thick metal crossmembers, hot shards of metal spinning off the drill bit and landing on exposed skin.  My body hurts and so does my pride!    

See, a lot of folks go the route of framing their floor, tacking metal roll flashing to one side and then flipping the whole assembly onto the trailer so that the flashing is facing the ground.  But Nate pointed out that I would only have 3.5" of insulation in my floor using this method and that I would be surrendering the opportunity to insulate the space created by the steel crossmembers of the trailer frame (for a total of 6.5" of insulation in the floor).  I agreed that would be ideal and set to work trying to figure out how to put the metal flashing layer on the very bottom of the trailer.  This would not only provide a moisture, insect, and vermin barrier, but it would also provide a convenient backing onto which I could place my insulation.

Nate pledged his assistance with the undertaking and I wanted to make the most of his expertise to wipe out this nebulous phase of the project with haste.  I visited a sheet metal dealer and purchased 3 of the biggest sheets they sold:  4'x10', hopelessly flimsy (26 gauge), galvanized sheets!  (In retrospect I may have gone with the thicker 22 gauge sheets.)  I also researched fasteners and queued up drill bits and drivers.

We went to work on it Sunday morning.  Nate and I laid out our first sheet and made the necessary cuts and bends.  Then we wrangled the massive drooping sheet under the trailer and set to work fastening it.  That's when things started going awry.  Nate is built like a brick house and was putting impressive force into the small screws I had purchased for the task.  Yet the screws weren't cutting through the metal.  We realized we would have to pre-drill all the holes!  Several broken screws and bits later, we only had a couple mangled screws holding the sheet on.  I was using a #8x3/4", 18 thread count, galvanized #2 tec screw, and if you don't know what means, it is too puny a fastener for cutting through 3/16"+ c-channel steel.  I returned to Portland Fastener and asked for something beefier, leaving with a #10-#3 tec screw (meaning the next size thicker in diameter and a more aggressive head for cutting through heavy steel.  I also purchased several bits made for drilling through hardened metal (cobalt bits).  This re-tooling proved to be the winning combo to make real progress on attaching the sheet metal, but it was still a slow, laborious process, and I think I still didn't have a robust enough fastener for what I was asking of it.  The new screw still couldn't bore through the metal on its own and therefore required a large pilot hole.

Lesson Learned:  These days you can buy a tiny-house-ready trailer from some manufacturers.  Among other customizations, they can weld on a sheet metal underbelly.  If I did it again, I would probably spring for this feature.  I appreciated my method because I learned a lot about fasteners, drill bits, and manipulating sheet metal, but the effort and time expenditure were bordering on the ridiculous.  The slim advantage of my system is that I could remove the fasteners and drop the pan to do maintenance.

A big shout out to my friend Nate for his patience, teaching, and willingness to help me through this challenging phase of home building.  Without his help, I'm convinced I would still be scratching my head about the whole affair or be stuck with only 3.5" of insulation in the floor (which is probably acceptable if you spring for rigid foam insulation).