Case Study: Tiny House Trailer Design
Laying a proper foundation is the most important step in any new venture . . . Of Course . . . And this is how we put the sure foundation in 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 the engineering and design help in making sure their new “Tiny” homes have that sure foundation. They want something different, something more stable, something stronger 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” aspect that make the designs good. It’s the integration of the cool with the first and root need for a sure foundation.
This “Case Study” shows some of the thought processes of Trailer Design as it is applied for the specific purpose of Tiny Homes.
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:
- The load is usually applied once, and it stays there, but it’s not static. (That’s not the case for a utility trailer or a car hauler or most other trailers typical for building a tiny house.)
- Loading on a trailer supporting a Tiny House is largely at the perimeter, not evenly distributed over the width and length of the bed.
- While most trailers do sit for long periods of time, the Tiny House is usually quite 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 other types of trailers, a little flex as it goes down the road is not a problem. Think pot-holes and bumps. As bumps occur, and as loads move, they flex slightly. A little trailer flex is no problem for a car hauler, because the load doesn’t care. However, in a Tiny Home, cracks appear in walls or ceilings, and windows can twist slightly and break. Stiffness is much more important for this application.
- Finally, a low bed is good for many trailers, but the Tiny Home has a unique need because the bed is the start of the floor. Tiny Houses often push the legal limits for height as they include lofts and vertical expansions. Gaining a few inches with a lower floor is very desirable.
- Maximize width within legal limits.
Designing To The Requirements
As a synopsis of the above requirements, the trailer must be super stiff, especially to accommodate the 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 for production must allow all sorts of floor plans, options and configurations including a low deck 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 they are used. A great Tiny House Trailer must accommodate all the above as well as all the normal functional and towing stability features.
Truly, designing well for a Tiny Home brings another level of thought and greater need for attention to the fine details.
Conquering The Floor
In the process of study and design work for the specialty one-off trailers, we’ve also come up with a few clever ideas of our own. Most important is a method to to accomplish #6 above, which is a very common concern. “How do you maximize vertical space available for the Tiny Home?” Or, stated more specifically, “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 2:
- 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 construction lighter.
- Second, construction process uses a more advanced technique of laser or waterjet cutting features with the main beams. We use this technique a lot as we build specialty manufacturing machines, so we know the value. And, it’s not really that advanced since the technology and machines have been around for decades. However, they are not normally found in the same shops that 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 can reduce the home floor height by 6″. Additionally, it provides a 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 height is your concern, our plans incorporate more than just the integration as a way of lowering the floor. The lower floor allows more vertical space, it’s true, but that’s not the only opportunity. Using the available legal width is the other. Our trailer 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 the space available to maximize comfort.
The Right Support In The Right Places
Another big issue we address head on is that of perimeter support for the walls, and the method of anchoring the house to the trailer. First, the perimeter support.
Designs by Synthesis analyze the frame with loads applied significantly at the perimeter. Our designs don’t leave the perimeter loading as a side note, it’s part of the fundamentals.
For a house, the walls carry a very large portion of the total house weight. Certainly the roof, any loft, snow and wind loads, hanging storage, shelves and other forces come to the frame through the walls, at the perimeter. This is why we place a strength priority on the trailer frame perimeter support. And, we anchor the walls securely so the house truly has a strong foundation.
We use cross members designed to carry the full perimeter load. 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 early while working for the 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 accommodation for re-tightening over time. (Maybe cutting holes in the walls to find the studs and tighten things? I don’t want to punch holes in my walls to search for studs to tighten.)
The solution is ridiculously simple. Anchor a nut in the wall solid to the board, and allow access to the bolt from underneath. You can use the little mushroom nuts with the spikes if you want, but they have their own issues. 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 boards. Either way works.
With the nut plate 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 design out and 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 culminates with 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 the Tiny House Trailer Plans described above. They are sold through our Mechanical Elements website, and are available for immediate download.
Of course, engineering is what we do, so yes, these new plans are complete. They include consideration for all of the above requirements as well as many more. The resulting trailer is heavy duty to carry whatever your house requires.
Don’t settle for building your house on a car hauler or large utility trailer. Don’t guess at loading and assume it will be good enough like so many others (on YouTube and around the internet). If you’re going to invest in building the house, make sure you start on a sure 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.