Wall Raising

"Standing" in my door opening
I decided to use conventional wood stud construction to frame my house. It is what I am familiar with although I am interested in other methods like steel studs or SIPs (structural insulated panels). My build buddy, Lina, decided to design her house with SIPs and so I was able to learn more about them at her wall raising.
Raising the first wall!
I designed my house around dimensional lumber sizes so that I could reduce the amount of waste which has proved successful since it has been difficult to find scrap pieces of wood on site! Since my design is for a shed or skillion roof, one of my long walls is taller than the other. I used 2"x4"x8's for the short wall cut to stud length at 92 1/4" (some people use 92 5/8") so that the plywood sheathing would span from the bottom plate to the middle of the double top plate. Then I will rip another piece of plywood for the top once I have the rafters and blocking in place. I had originally designed this wall to be 9' from bottom of bottom plate to top of rafters so that I could use a single piece of 4'x9' plywood but then I learned that 9' sheets of plywood are actually not standard, need to be special ordered and cost twice as much as 8' sheets. I didn't want to lose a whole foot on that side so I compromised with the more conventional framing method. 
Raising the tall wall!
For the tall wall, I used 2"x4"x10's for the studs and had to trim off some of the ends since they were a little more than 10' long. I decided to go with an advanced framing method where I have the studs spaced at 24" on center vs. the 16" OC studs. This method minimizes the amount of lumber necessary and keeps the weight lower. Had I built this house on a fixed foundation, I would have used even less lumber due to wheel well considerations. I decided to put double studs on each side of the wheel wells to support the header hanger for the 2x6 spanning the 5' distance. Had the trailer been designed with 48" behind the wheel wells instead of 46", these extra pieces of lumber would have lined up with the layout. I also should have put full double studs in the corners for the tension ties since a single stud did not push the hanger in far enough to avoid drilling into the rear lights. (I originally wanted to have a 2 stud corner, one for the end of each adjacent wall to reduce thermal bridging.) I could probably have put the tension ties somewhere else with a double stud like at the wheel wells but I think code requires them within 1' of the corner. A friend suggested adding a 2x4 block to fur out the corner so that is what we decided to do. I am unsure of what this does structurally but I think that my sheathing will help.
Wheel header detail
Other considerations I had for my framing layout were the locations and sizes of my windows and door. I ordered two of my windows to be 48"x18" and three of them to be 24"x30" so that they would fall on my framing layout. However, I realized that I probably should have ordered them to be 22 1/2" and 46 1/2" wide as rough openings to account for the 1 1/2" total thickness of the studs on each side. But, since they are in bearing walls, I designed them to have insulated headers, trimmer studs and cripple studs under the sill edges in the center. As long as the framing layout landed on one of those members, I could not have really reduced the amount of lumber used. I learned from a structural engineer after framing that I could have used header hangers for the windows as well which makes sense. (He also said that the wheel well header hangers were overkill.) Had the windows had 22 1/2" and 46 1/2" wide rough openings, I could have used the studs as the vertical edges and a single flat 2x4 on top and bottom of the opening. This is very light framing and I worry that it would not be enough for a mobile structure to keep windows in place and from cracking. Since I put a lot of time, energy and money into my new windows, I did not want to test this method out. When I draw up new versions of my plans, I plan to try out both designs and see which one is more ideal.
Window framing
I still have not found a used door that I like and cannot justify spending over $500 for a new door so after I learned that standard entry doors are 32"x6'8", I made my RO 34" wide and 82 5/8" high until I find a door to fit.
Rafter framing
The rafters line up with the studs so I did not really need a double top plate but I decided it would be a good idea on my two long walls since they bear the roof load and because my house is mobile. Since I had designed the wall system the way I did, the angle of the roof pitch ended up being approximately 4:12. Since my roof only has one slope, the exact pitch was less of a concern. To make the rafters, we put a 2x4x8 on edge spanning the two long walls. With squares, we marked the end plumb cuts at the outside edge of the stud framing. (I did not design an overhang since I am wrapping the exterior with insulation to create a thermal break.) Again, since I had planned for minimal waste, they were just barely long enough. I cut the plumb lines and then marked the seat cuts for the birds mouths perpendicular to the plumb cut. Those were the only two cuts I needed to make for the short wall side but I had to make another plumb cut to line up with the inside of the tall wall. With this first piece as a template, I used it to measure and cut the remaining 9 rafters so that it could also be used as a backup piece if necessary (and it was). We installed them in place with Timber-Tite screws which was much faster than using the hurricane ties.
Timber-Tite screw
I framed the end walls in place with a single top plate since they are non load bearing and that is what I have seen in my research. I started by cutting the bottom plate to length and screwing it into the subfloor and floor box. Then I figured out the angle for the top plate and studs with scrap pieces. It ended up being 18 degrees. I measured and cut the top plate and two end studs. Then I installed these to create the outside frame. I needed three other studs per wall so I held them in place while I plumbed and marked the cut line. I learned that starting with the taller studs and working down to the smaller ones is beneficial if you accidentally cut one a little too short. Once these were all cut and installed, I added blocking at the 8' line so the top of the plywood sheathing would have something to tie into. It was a time intensive process but I was able to do it all by myself.
Framing in the rain
A note about fasteners. Screws take much longer to frame with than nails. Screws are usually used in mobile structures since they have more grip to stay in place over time. I used ones which required Phillips bits and would never do this again since they strip the screws easily and I have destroyed about 5 bits so far. Better screws to use are those with square or star drive heads. I would also like to more research into ring shank nails since I have used them for flooring and they are kind of like a nail/screw hybrid. I will likely be using them for my siding.

For more photos, check out my flickr!

Floor Box: The Boots

Figuring out how to build a light, well-sealed, energy efficient floor for a tiny house on wheels can be quite challenging. I knew I wanted to inset the floor into the trailer frame instead of placing it on top so I would have more head room since I designed my house to have a loft. I think this is also a more secure connection to the trailer although my walls are mostly independent of the floor system (the subfloor will probably be toe-nailed to the the bottom plates) since they will be bolted to the angle iron flange.
I originally thought I would build a floor box out of 2x6's with rigid foam as insulation (lightweight and high R-value) and a thermal break from the trailer and the metal pan undercarriage, but then considered another system using fiberglass reinforced panels glued to several layers of foam and then covered with the subfloor. My build buddy Lina had seen a similar system recently and wanted to try it out as a lighter weight, lower cost alternative so I decided to give it a go. Unfortunately, we could not find a glue that would stick to both the foam and the fiberglass panels (we tried out the foamboard adhesive and liquid nails). I even called the panel manufacturer to ask about what adhesives would stick and he told me I would need to call the adhesive manufacturer which was not very helpful. In this process, we also learned that having the ribs underneath the trailer spaced at exactly 24" on center would have been very helpful since sheet goods typically come in 4'x8' pieces and having them break on the ribs would be great!
After that experiment, I decided to build a modified floor box. I built two square frames out of 2x6s and bolted them together in the middle. I used 8' pieces of lumber since they are typically more straight than 16' pieces of lumber. I screwed in three parallel and flat 2x4s to the bottom of each frame box so that my undercarriage could have something in the middle to screw into. I did this instead of adding more traditional 2x6 floor joists so that I would have a thermal break from the trailer and undercarriage. After we put the wood frame together, we flipped it over and attached the two 43"x15'7" 26 gauge galvanized aluminum "galvalum" sheets to the frame with sheet metal screws that had neoprene gaskets. I thought the gaskets were a great idea to prevent water from getting in those holes. It probably would have been a good idea to run a bead of silicone on the framing prior to screwing as another layer of waterproofing but that would have been difficult with only two people and a long awkward sheet of metal. I can easily replace the screws as needed since we made sure they would all be visible. We did liberally apply silicone between the seam overlap down the center.
I purchased the galvalum from REM Steel after a tip from Kevin, one of the founders of Green Anchors where I am building. I chose this material because it is lighter and more durable than galvanized steel. It also comes in rolls that I can fit in my car! I had thought about having metal pans built which would have been heavier since they would have been 22-24 gauge. They also would have been several times more expensive ($450) than the galvalum which was just under $100 for the 2 pieces I needed. And I would have needed a truck to haul them to site. Having a truck would be great to have for this build but I am making my Subaru work out fine. And many places will deliver for free or not much money if you order enough materials. That is why I am using new framing lumber instead of searching Craigslist for free or cheap stuff. I think it would be a fun project to use Craigslist to build an entire house so maybe I will have to trade in my car for a truck next year and make it happen!
I left a 1/2" galvalum overhang from the wood frame since I wanted to put a 1/2" strip of rigid foam between the wood and trailer frames for a thermal break and I wanted it to protect the foam. I plan to silicone the seam and check on it periodically to ensure it stays sealed to prevent water from getting in the floor. With the help of Rory, our neighbor who is a metal worker, we flipped the floor box over again (galvalum down) and set it in the trailer. I had allowed some wiggle room since the trailer and frame were not quite square and it fit easily.
Then, we cut pieces of 1/2" foam for the perimeter and realized I should have left some more wiggle room between the framing and trailer since the foam was more like 5/8" than 1/2". But with pry bars and creative clamps, we made it happen! Since I had Rob drill 5/8" horizontal holes in the trailer for bolting the floor box, I used a spade bit through the predrilled holes to drill through the wood frame and then inserted 1/2" carriage bolts with locking washers. Next, we added a layer of 2" foam between the flat 2x4s, then we cut and installed 2 layers of 1" foam. (Lina and I had to do some foam trading for various reasons and we wanted to use what we had, otherwise this would have been a single 2" layer.) 
For the top layer, we installed another flat 2x4 in line with where the subfloor sheets would break so they would have some wood to tie into and so hopefully the floor will not be squeaky due to the foam layers (although many wood framed floors are squeaky due to joist hangers and little or no glue). Then we cut 4 pieces of 1 1/2" foam and set them inside the wood frame. Finally, we cut 4 sheets of Edge Gold subfloor to length and used liquid nails and 2" screws to glue and screw the sheets to the framing. We started with the sheet with the cut off tongue in the front and worked to the back of the trailer, leaving 1/8" gaps for expansion and contraction. Due to these gaps, we needed to cut off 3/8" from the back end which was the approximately depth of the groove. I am glad I chose to go with a 16' trailer and kept the floor between the wheel wells so we did not have any odd cuts to make.
The last steps were to cut more pieces of 1/2" foam to fit between the subfloor and trailer since the subfloor extends past the 2x6 framing by about 2 1/2". This foam continues the thermal break between wood and trailer frames. It also eliminates the need to rip down the 2x6s to 5" to match the height of the tube steel which I thought was unnecessary work. And then to use some Great Stuff to seal up the perimeter.
This weekend, we will build and raise walls!
For more photos, check out my flickr!