Simpson Strong-Ties or steel hold-downs should be utilized in your tiny house build. They will do three things: make your tiny house a wind warrior (secure your investment), add a lot of time to your framing process, and tap into your pocket book. We ended up spending $850 for steel hold-downs along with the appropriate nails and screws to fasten them. Like the trailer, this isn’t a time to skimp. If you use SIP panels, you may need to research for even more steel hold-down options.
Subfloor Hold-DownsWall Assembly Hold-Downs
Proper Hold-Down Fasteners
Check below for additional pictures where you can see hold-downs utilized. The reins are ours,
Reflections, Hindsight, and Alterations:
Initially, I didn’t spend the money for the proper fasteners on our subfloor (a regret). There is a very big difference between the quality of Simpson’s nails and screws and regular ones.
We scored extra hold-downs from a builder friend, so I was adding a lot of 90 degree hold-downs to a lot of extra spots in the framing for additional structural integrity.
We saved a lot of money by getting certain hold-downs on online at Hardware Online Store. Make sure to check online store’s shipping rates–they can be game changers.
It feels really assuring to have the hold-downs throughout the framing!
Very few splitting issues with the nails. Sometimes, we pre-drilled holes for the screws. We mixed nails and screws in some of the hold-downs to get different types of holding power.
After receiving our lumber, the plywood and wood needed to be acquainted, so we left the plywood on the trailer for a week to see if they liked each other…any gullible readers? I hope so. The first step was to correctly cut and lay out all of the plywood on the trailer without the obtrusive bolts complicating things (I’ll weld them on later). I mapped out two ways to lay the plywood efficiently. I did this before purchasing the lumber to help calculate my plywood count. I ended up using a slightly adjusted “longitudinal” approach to make sure the plywood seams ended up on the trailer’s metal joists.
Orientation Option 1:
Orientation of Plywood Option 2:
Confession: Permit-less Punks
If your trailer is a typical eight foot wide one, it’s a lot easier to lay out your plywood. Our trailer is wonderfully and awkwardly eight ft, four and 3/4 inches. With our roof overhangs we will be pushing the state’s limit of 8 ft, six inches. Because we rarely plan to move the house, we’re comfortable with pushing the width limit to gain as much interior space as possible. Will this “inch pinching” decision come back to haunt us? I hope not, gulp!
The Beginning of Endless Wood Cuts
Ignoring 100,000 demanding future cuts for the house, I emphatically engage with the initial large and heavy plywood puzzle.
Circular Saw and Jigsaw
Powered Drill with Your Bolt Size Bit (5/8 in) *A little bigger
4 ft and 2 ft Square
Cutting Guide with Clamps
Unbeknownst to me, after the wheel wells–the trailer starts to taper as you approach the angled hitch area! So, it wasn’t square and flush with my plywood’s factory edge pieces–which was really throwing me off. I thought the whole trailer might be out of alignment and warped. Panic anyone? Because my glass is half full, the trailer tapers only a half an inch on each side gradually over the last four feet–not so bad, so instead of moving the whole house’s frame inward, I tossed the dice, letting it hang over (the bottom plate will still be 85% on the steel frame and bolted to it). Surprisingly, the turmoil led to an idea.
Inch Pinchers Become Foot Pushers
“This overhangs. Why not gain some feet in the front? Extend the overhang!” exclaimed Chris.
“Wow. The extra feet would be nice! Would it effect turning and driving the trailer?” Michelle said.
“That’s what I was wondering about…I don’t know. If we only do two feet, it shouldn’t, but I don’t know. Should we go for it?” Chris said gazing at the hitch area while day dreaming about even more space.
“Yea!” Michelle said…day dreaming about more space.
Let’s hope our space ambitions really don’t haunt us–but yes, although in all of my tiny house research I have never come across any instances or examples of it, Michelle and I have taken the risk of expanding the house over the trailer two feet. This will give us 22 ft total. The angled steel framing near the hitch is four feet in length, so we’ll still have two feet–hopefully this is enough for all turning we’ll need to do on the road.
Finally, I drilled holes where I plan to weld the bolts. Had to buy a drill bit that was slightly larger than the 5/8 inch threaded rod. Initially, I was using a 5/8 inch bit and spinning it around to make a larger hole–not something my arm wanted to do sixteen times–doubt the drill liked it either.
The reins are ours,
Reflections, Hindsight, and Alterations:
Although the extra space will be nice–the extra width may cause a lot of problems while driving–and it makes more wood waste because it’s over eight feet. Would have enjoyed an eight foot wide trailer for its simplicity.
“Yack, yack, yack,” said the subfloor generic lipitor.
“Wait a minute. What do you mean?” responded Chris.
“Have you heard of steel hold downs? What are they?”
“Ya, ya, all the time. They’re steel. They hold down stuff, ya idgit.”
“I give up.” Chris concluded.
Common sensibly, fastening your house to the trailer needs to be well engineered and figured out. After consulting countless tiny house builders’ experiences, I found 2cycle2gther’s article and the Tiny House Blog’s Phase 1: Subfloor Sandwich System to be extremely helpful. Although we wanted to incorporate that precious 6 inch space between the steel trailer’s framing members, Michelle, a building science graduate student, informed me that steel framing (studs) destroy your insulating capacities where you’d want it: under your toes in the winter. Joe Lstiburek, building science guru, states, “insulating between steel studs is a thermodynamic obscenity.” Because there’s no way to fully enclose the trailer’s hitch from the elements, the trailer frame space wouldn’t be a part of our subfloor.
Exemplifying redundancy, we’re combining an altered sandwich system with 2cycle2gether’s sheathing to trailer screwing as well as screwing the entire subfloor to the trailer with Teks #12 (wood to metal 2 3/4 inch screws). We will also weld 16 bolts to the trailer to hold down the sill plate and entire subfloor to the trailer. No chances have been taken! Why choose some approaches when you can employ every single one?
Longest Sandwich Creation of My Life
Bottom Bun: Galvanized Steel Flashing
The bottom bun of our subfloor is galvanized steel flashing (seemed like the stronger and better option than aluminum although it was a little more pricey). As I understand it, the flashing will keep out insects and provide some water protection. You can skip the flashing and paint the 3/4 inch plywood layer with a strong and nasty marine grade of paint…if you’re into nasty. What’s strongly stated with flashing types is aluminum reacts poorly to the chemicals used in pressure treated lumber. Our bottom T&G 3/4 inch plywood is treated, so aluminum was a no go; however, galvanized steel isn’t flawless according to the web, so for safety, we used tar paper in-between the plywood and flashing. As always, better safe than sorry.
Portobello Slider: 3/4 Inch T&G Plywood
The 3/4 inch tongue and groove provides a lot of structural integrity. Having it or one side of it treated supplies extra durability if water penetrates.
Tomatoes and Pickles: Glulams and Foam
On top of the 3/4 inch plywood will be the framing of the subfloor. I will use homemade glulams and 2x4s and glue and screw them to the 3/4 inch plywood underneath. Additionally, 90 degree steel hold downs will secure everything to everything. Insulation will be foam boards–and all remaining seams will be spray foamed in. I’ll use 16 inch on center joists–this may be a waste of wood–but I’m playing all of my structural integrity cards.
Top Bun: 1/2″ plywood
On top of the framing will be only 1/2 inch thick plywood. Because the insulation is rigid, 3/4 inch plywood on top wasn’t necessary. All seams and joints will be caulked or siliconed for top notch air sealing (one of the most important, if not the most, energy efficient measures for a house). This plywood layer will be glued and screwed to the framing.
Side of Chips: The Welded Threaded Rod
Choosing the way to bolt the trailer was stressful. We didn’t use bolts because our steel is 6 inches thick and the subfloor was 6 1/2 inches; buying 13 inch bolts would have been expensive; however, it’s a good way to prevent welding cost (unless you weld them yourself–threaded rod is cheaper). We placed the bolts in obvious spots: corners, near the wheel wells, and in-between those areas. We decided to weld the bolts (threaded rod) for added strength. We’ll use Simpson’s HTT5 hold downs with the bolts, so that’s a huge cost in itself. Although on a tight budget, these were the areas we wanted to spend our money.
Future post will have detailed specifics on each of these sandwich steps. Yum, yum.