Case Study: Tiny House Trailer Design
Laying a proper foundation is important in any new venture, of course. And, that is definitely the case for the foundation of a Tiny House Trailer Design! For a Tiny House, the trailer is the foundation — both literally and figuratively. What could be more important than getting the foundation right?
We have a few customers who understand this concept. They come to Synthesis for engineering and design so their new “Tiny Homes” have that solid foundation. They want something different, something more stable, something stronger and better for the foundation.
At Synthesis we’ve designed several Tiny House Trailer Foundations that include some pretty cool and unique features. But, it’s not just the “cool” things that make the designs good. It’s the integration of cool with the first and most important need for a solid foundation.
This is a “Case Study” showing some of the thoughts in designing a better trailer for Tiny Homes. Come, and follow the thinking.
What Makes A Tiny House Trailer Design Different?
The first step with any design is to understand the requirements. You can see our emphasis by reading Defining Product Requirements in the very popular Product Development Process Article in the Synthesis Engineering Library.
Here is our partial list of requirements — including things that are different for a Tiny House Trailer Design:
- For a Tiny House Trailer, the load (house) is set once, and it stays there, but it’s not static. (Utility trailers, car haulers and most flat beds are designed for periodic loading — which is a little different.)
- Loading is mostly at the edges where walls attach. Some loads are in the center, but most loading is not evenly over the bed.
- While most trailers do sit for long times, the Tiny House is usually active even while it sits.
- When the Tiny Home trailer is sitting, it remains fully loaded. (Most trailers are empty while they sit, and typically they sit undisturbed – stored.)
- For most trailers, a little flex is no problem as it rolls down the road. Think pot-holes and bumps. As bumps occur, and loads move, they flex slightly. A little flex is no problem for a car hauler, because the car doesn’t care. However, in a Tiny Home, cracks appear in walls or ceilings, and windows can twist slightly and break. Stiffness here is much more important.
- Every inch counts, so foundation trailers need maximum width — within the legal limits.
- Finally, a low bed height is good for many trailers, but the Tiny Home is unique because the bed is the start of the floor. Tiny Houses often push the legal limits for height as they include lofts and vertical expansion. Gaining a few inches with a lower floor is very desirable.
Designing To The Requirements
In summary, the trailer must be super stiff, especially for perimeter loading. It must be stiff to accommodate the always live loads with activities in the house; wind, snow and other environmental conditions. It must be strong to hold significant loads all the time, and to travel flawlessly. Finally, it must allow all sorts of varying loads like tanks, batteries and storage.
Oh, and a Tiny House trailer design must allow all sorts of floor plans and options with a low deck height to allow customers to include a roomy loft if they want. Most Tiny Homes are unique, not only in floor plan, but also in construction and in ways people live. A great Tiny House Trailer must handle all of it — as well as the normal functions and towing chores.
Truly, designing well for a Tiny Home brings another level of thought and greater need for attention to the finer details of the trailer.
Conquering The Floor
In the process of study and design for these special one-off trailers, we also have a few clever ideas. Most important is a method to do #7 above, which is a very common concern. “How do you get the most vertical space for a Tiny Home?” Or, stated more directly, “How do you get the house floor as low as possible?”
Our answer is to integrate the floor support right into the trailer frame. That in itself is not so unique, but we also combine it with making the frame both easier and faster to build. Interestingly, our method also assures a better, straighter and flatter floor. So, what’s the trade-off? There are two:
- First, the frame of the trailer integrates and some of the total weight moves from the house to the trailer. It does make the trailer a touch heavier, but in the process, it makes the house lighter.
- Second, the build process now has a more advanced technique with laser or waterjet cutting for the main beams. We use this technique to build specialty manufacturing machines, so we know the value. And, it’s not really that advanced since the technology has been around for decades. However, they are not normally found in the same shops that will weld and grind and blast their way through building trailer frames. A little coordination between shops, and you’re good to go.
Integrating floor supports into the trailer frame also reduces the floor height (effective deck height) by approximately 6″. Additionally, it provides superior stability, potentially a flatter floor, and better wall anchoring. Read more about walls below.
Addressing Space in Tiny House Trailer Design
As a side note, if space is a concern, our plans have more than just a low floor. The lower floor allows more vertical space, it’s true, but that’s not all. Using the available legal width is another. Our plans show frames that are 1″ less (each side) than the legal limit in width. That allows wall exteriors at that width, then siding to extend beyond — to cover the frame edges, yet remain within the limit.
Yes, it’s supposed to be tiny, but there is nothing wrong with using available space for comfort.
The Right Support In The Right Places
Another big issue we tackle head on is perimeter support for the walls, and anchoring the house to the trailer. First, the edges.
Designs by Synthesis analyze the frame with loads primarily at the outer edges. Our designs don’t leave perimeter loading as a side note, it’s part of the fundamentals.
In a house, the walls carry a very large portion of the total weight. Certainly the roof, the loft, snow and wind loads, hanging storage, shelves and other forces come to the frame through the walls. This is why we place a strength priority on the trailer frame perimeter. And, we anchor the walls securely for a truly strong foundation.
We use cross members designed to carry these loads. It’s not an afterthought.
A Tiny House trailer design often has threaded studs welded to the frame as anchors for the walls, much like a standard stick built house. It’ a great idea, but it has one rather important shortfall — wood changes over time, and especially with weather and movement. Yes, movement, and trailers introduce a lot of that.
I learned this lesson working for farmers where I grew up — bolting to wood often requires re-tightening. While studs on trailers look like a great idea, and when they’re new, they feel like a great idea, there is no way to re-tighten over time. (Maybe cutting holes in the walls to find the studs and tighten things? I don’t want to punch holes in walls to search for studs, do you?.)
The solution is ridiculously simple. Anchor a nut in the wall solid to the footer board, and allow access to the bolt from underneath. You can use the little mushroom nuts with spikes if you want, but they don’t always work well. I prefer a small steel plate with a lock-nut welded on. Make it larger than the space so it can’t twist in the wall, or add a screw hole off to the side to anchor it to the footer board. Either way works.
With nut plates in place, you can simply go around the trailer frame once a year and tighten each bolt if it needs. The house will always be solid to the trailer.
Tiny House Trailer Plans Available
The end goal of the exercise is an awesome Tiny House Trailer Design — one that provides a sturdy foundation for building a house to last a lifetime. Secondly, get the plans into the hands of those building Tiny Homes. With our engineering tools and expertise, we’ve created plans for a couple trailers designed specifically for the Tiny Home marketplace.
This case study ends with some really great Tiny House trailer plans that are now available to everyone.
If you’re thinking about joining the Tiny House movement, we have something special for you. At Synthesis we have developed some awesome DIY plans over the years, and have now expanded that line of Specialty Trailers to include these Tiny House Trailer Plans. They are sold through Mechanical Elements, and are available for download.
Engineering is what we do, so these new plans are complete. They include consideration for all the requirements. The result is a heavy duty trailer ready to carry whatever your house requires.
Don’t settle for building your house on a car hauler or large utility trailer. We don’t guess at loading while thinking it will be good enough like many folks on YouTube and around the internet. Instead, we do the engineering. If you’re going to invest in building the house, make sure you start on a strong, solid foundation.
Good Luck with Your New Home Project.
Among other Engineering Services, Synthesis does specialty trailer design. Please feel free to Contact Us if you need a custom tiny house trailer design to meet your specific requirements. We’re happy to help.