Sill Plates: 75%

(~6 hrs)

It looks 100% done, but the end pieces aren't bolted down yet.

Sill plates. If you'd asked me what the quickest and easiest step in building the walls would be, I'd probably have said the sill plates. What could be simpler? Just glue and bolt some 2x4s around the edges of the floor, keep them half an inch from the edge, and... there you go!

Plus, the wheel well arches are obviously the hardest part of the sill plate, and I had my plan all laid out for those ahead of time. Boom, taken care of.

So. Dad and I worked for about six hours today--not including a couple runs to the hardware store for supplies--and we got the sill plates about three quarters done.

The first and every lesson is: expect everything to be slower and more complicated than you think, if you've never done it before (and especially if you lack basic skills or physical strength...)! 

Headers for the wheel well arches

Our first task of the day was to build the headers for the wheel well arches. We didn't need them first--I just wanted to give the glue some time to dry before we installed them.

To make them, we cut 2x4s to length (67" for me), cut a sheet of scrap 1/2" OSB to 67" long by almost 3.5" wide, and sandwiched them together into a beam. We glued the layers together (OSB in the middle) and then nailed them together. Specifically, we used 3.5" 16d hot-dipped galvanized nails.

Lesson 30: Screws would have been way easier than nails. The knuckle I whacked while hammering agrees.

Any beam composed of several separate pieces will be hard to make perfectly by hand. While we were getting the pieces at one end nice and even, the other end would slide apart. We focused on getting the sides even around the circumference of the beam--we cut the OSB a little narrow to help it not stick out--but the ends came out ragged. The beams do the job, but they're not beautiful.

Lesson 31: If you have enough materials, make your beams a couple of inches too long and then cut them down to the correct size after they are glued and screwed/nailed together.

Then we started in on the rest of the sill plates.

With SIPs, you are supposed to set your sill plates a certain distance back from the edge of the subfloor. That distance is the thickness of the OSB skin--for me, about 1/2" (actually 7/16"). The panels slip over the sill plate and then your wall is flush with the edge of the subfloor. Now, if your subfloor is the image of lovely, perfect squareness (i.e. all corners are 90º), then great! Maybe you're the lucky person who can just plunk your sill plates down 1/2" from the edge all around and call it good.

Unfortunately, my subfloor was not perfectly square. Boo. I realized some time after we built the subfloor box--the strong, totally unshiftable subfloor box--that the subfloor plywood actually overhangs the edge of the trailer on one side at the tongue end and doesn't quite make it to the edge on the other side--both by about 1/4". That, and other fudges, I'm sure, contributed to the subfloor being a bit out of square. Plus, there is about 1/4" of "creep" originating from the slight gaps between sheets of plywood--that is, the plywood hangs over the front of the trailer by about 1/4", too.

But the SIPs are very square, and they need a very square arrangement of sill plates. And it turns out that it's not all that easy to figure out how to fit a square on a not-square and still preserve all the requisite measurements.

First piece, situated and ready to be drilled

It kind of drove us crazy.

We started from the back end, which we knew was pretty square, and got one piece of sill plate installed along the long side, behind the wheel well. The solution we eventually reached was to measure everything in relation to that piece. We knew how far apart the outside edges of the long side sill plates should be:

96" - (7/16 +7/16) = 7' 11 1/8"

And we knew how long the sill plates have to be, based on the size of the panels:

• 8' at each end
• 8' 10" in front of the wheel wells
• 4' 10" behind the wheel wells (we went a little short on one of them, oops--we'll have to squish the panels together tighter there to get them to fit)
• 5' 7" over the wheel wells

So as long as our pieces were the right size, and they were perfectly parallel to each other and 7' 11 1/8" apart and at 90º to the back panel... we were good. When we build the walls, we will simply leave the front end for last and install its sill plate wherever it turns out it's needed. Thank goodness we have that 1/4" of extra wiggle room, right? Totally intentional...

But believe me, we measured and remeasured and remeasured again so many times before we decided on that simplified approach. Oh boy. 

While we were determining the position for each piece, we tacked it down with a couple of 2" screws. It's easily reversible if (when) we needed to shift the piece. When we were happy with where the piece was, we drilled through the 2x4, subfloor plywood, and trailer to create that final alignment. More on drilling and bolting in a moment...

1/2" OSB scrap as spacer

Lesson 32: If you're placing sill plates for SIPs, have a piece of scrap OSB the same dimensions as the SIP skins handy. I realized that we could use the piece of scrap as a spacer to make it easier to imagine where the panels will be in relation to the sill plates. We positioned the back sill plate and first side sill plate using that piece of scrap by holding the OSB against the 2x4 and shifting it until the OSB was flush with the subfloor edge. We also used it as a spacer to make sure the 2x4s were the right distance apart at the corners, where one SIP will butt up against another. Pretty nifty!

Gap between sill plates at the corner

Since the subfloor wasn't perfectly square, the outer OSB skins of the panels won't be fully supported by the subfloor in some spots. I hope that's okay. I figure it's probably more important that there not be gaps between the panels due to non-squareness. Probably?







So, bolting. These sill plate bolts are the main connection between your walls and the trailer, so this is serious business--don't skimp.  Dee Williams, of Portland Alternative Dwellings, recommends using 5/8" bolts, and I've heard of placing them on 36" centers.

We couldn't get hold of a big enough drill for those hefty bolts, so I opted for slightly smaller bolts on closer centers. I used 1/2" bolts and placed them on 17.5"-24" centers, depending on the length of the sill plate section. That is, if the section was such a length that three evenly spaced bolts would be greater than 24" apart, I used four evenly spaced bolts at whatever-that-makes-it apart.

The big drill at work

Lesson 33: Drill a smaller hole all the way through first, then go at it with the full-sized (1/2" or 5/8") drill bit. That's the advice we got, we did it, and it worked.

Lesson 34: If you're not experienced with this sort of thing, it's helpful to have a spotter to let you know if you're holding the drill perfectly perpendicular to the floor. I was a little off on a few of my bolt holes, and it was okay in the end, but it's better to have things nice and straight.

Lesson 35: Big drills can really do a number on your hands, wrists, and forearms. Dad has arthritis and the big drill with the 1/2" bit bound up and twisted painfully on his bad wrist a few times. Have someone strong do this job, unless you have a super nice drill with an extra handhold and lots of torque.

Oh, and also:

Drat!

Lesson 36: Make sure the hole goes through a part of the trailer that you can access to place the washer and nut. To the right is our first drilling mistake: we just went for the center of the sill plate, not realizing that the bolt would come out through the trailer width extension/flange too close to the trailer frame to actually get the washer and nut in there. Dagnabbit. Dumb mistake! Think ahead before you do--especially before you do something that's going to put a hole in your gatdanged trailer.

Make sure the hole leaves room for the washer and nut!

After we drilled the holes, we undid the short screws that were holding the sill plates down and applied plenty of construction adhesive to the bottom of the sill plate. Then we put the sill plates back down and used the bolts themselves to guide the plate back into the desired position.

We used thread locker compound (a nasty blue glue) on the nut threads...

Use, but don't touch or smell, this icky blue stuff on the nut threads.

Scrape up excess adhesive.

...And once everything was good and tight (use a ratchet wrench!), I went around and used a little piece of scrap plywood to clean up the squelched adhesive. I don't want anything getting in the way of the SIPs fitting nicely over that sill plate and all the way down to the subfloor!







  

Use the frickin screws!

Now, if it seems like the wheel well arches were forgotten... indeed, those beams were the last things to get installed. However, we attached the king studs and trimmers (vertical pieces) to the adjacent sill plates during the temporary-screw-down step. We used nails and glue to attach all the pieces together, although, again, Lesson 30, Take 2: Screws are way easier! Actually, I ran down to the hardware store to pick up some 3.5" screws for the last wheel well arch piece, and my goodness, it made the job easier. Wish I'd done it sooner.

Nails can do this, sometimes, too. Boo, nails.

Lesson 37: Don't suffer with a difficult and time-consuming method when an easy, quick method is an extra trip to the hardware store away. The laziness is not worth it, believe me.






 
Just a note: I used 2x6s for the trimmers not for extra strength, but to provide a nailing surface on the inside of the house for when I build the box around the fender.





First wheel well arch up!













 Here they are, finished! And just like I drew them! I'm so proud!

 Even Pippin approves.

 It was a dang fine day of work. Tomorrow we'll bolt down the back end sill plate and then maybe start erecting some panels!

Who knows. Maybe the sill plates really were the easiest step, and I just don't know it yet... I'll find out soon enough!