Whats in this Post:
Laying the foundation beams on the trailer… Construction Day 1!! Very Exciting!Our trailer was built for tiny houses and is a double axle 20×8 set up for 10,000 lbs plus. It came with brakes and all the fixings. It has an open architecture and heavy angles welded at 16″ intervals. We used PT board here and double coated it. Those boards are exposed to the road.
It was trickier then it might seem to get these guys drilled and joined level. I had to clamp them into place in many instances. Even a slight crown or warp on an eight foot board can translate to a 1/4 discrepancy, which is just unacceptable. To keep my floor level from the start, these boards need to lay flat.
After getting my joists in place, I braced them in three courses. Along each edge I used gusseted angles and structurally rated exterior screws to brace each bracing beam. you can also see the connection of the Angle and the Foundation. I predrilled everything to prevent breakage and cracking. PT board can also cause long crews to sieze and strip the head. Always predrill PT. We used rated bolts and locking nuts, with a touch of locktite on each to join the foundation boards to the trailer. Later on we could potentially remove these 32 bolts and lift the house off the trailer. With this capacity in mind I made the Sub-floor structure about twice as strong as is normally called for, as you will see in later posts.
I didn’t have the energy to shoot pictures of all the techniques I used. I used heavy clamps and a small Plumb AND a small level on each connection to insure the squarest possible framing. I also obtained the wood for the braces from different lumberyard, and they were 1/8″ taller then the Joist beams. I therefore had to pay special attention to keeping the top surface level as possible and orient the excess 1/8 beneath. If we ever DO lift the house off, these spaces could be filled insulation and sealed to create even more floor insulation. That might be overkill though as our floor is already rated to 32+ R-value.
These last pictures show the side detail and completed structure of the exposed foundation of the tiny house.
1: We used Pressure treated boards for any lumber exposed to the road. This will help insure that water and debris don’t wreck your foundation too quickly. I gave these an extra coat of wood preservative before installation.
2: We used rated bolts and locking nuts if you have a similar situation with Angle pre-installed. No One wants their tiny house to break off and land in the back seat of their hauling vehicle or drop in the road and evolve into so much kindling in just a few seconds. There is a time to recycle and a time to buy new. We made sure the fasteners were tight and properly seated without over-tightening; any breakaway motion, even just a few millimeters and sudden stop, can cause kinetic damage to your structure.
3: All of our exposed hardware is galvanized to resist oxidation and the screws holding the foundation together should also be rated. I decided against using nails, because nails can work out of their holes a lot easier then screws with repetitive kinetic stress (driving!). I know nails bend where screws might break, So I took the time to use construction adhesives as well at critical junctures later on. I used Stimpson Strong Tie #8 Structural screws on the braces and 3.5″ Deckmate screws for connecting wood to wood. I also predrilled everything, as PT boards are tough and may crack or seize with long bolts or screws.
4: Getting the foundation level is key to having a level floor, so we took our time!
5: Don’t make it too wide. The law in almost every state are the same for width: 8′ 6″ So be absolutely sure you leave room for siding or trim or whatever fitting you need, otherwise Highway Patrol may issue you a fat ticket and require a “chase car” to ride along with a “Wide Load” sign on it to continue driving… no fun and possibly crippling if you have NO CHASE CAR available… SO Don’t make it too wide.
More Info: http://drivinglaws.aaa.com/laws/trailer-dimensions/