The Tiny-Builder's Sophie's Choice: Mobile or Site Built?

Every time I interact with a group of people at one of my How to Build Tiny seminars, I encounter people who say the same thing:

“I thought I was going to build a mobile tiny house, but now I realize I need to build on-site on a foundation.”

Cue the sitcom-esque trombone riff: womp, womp.

Why is this basic (and, I humbly assert, incredibly important) decision so often a mistake for DIY tiny house builders?

I believe it's because they have three main misunderstandings, and limited resources to help them make this determination. Well, search no more. I’ve got your back - the three faulty beliefs that make you think you should build mobile, when you should probably consider a build on-site:


1. “If I build a mobile tiny house, I won’t have to deal with any government people or building code.”

This is wrong on several levels. There is a national RV code, and most states have adopted it. Yes, RV code is less intensive than residential code, but it does indeed exist and it is enforceable. Following the code book becomes exponentially more important when you understand that most of it is for your safety (it’s sweet, really!).

Code is not necessarily your enemy, in fact. It is important to know that the typical American will sell the home they live in many times throughout their life. If and when it comes time to sell your tiny house, your buyer will want the reassurance that it was properly built.

It's also helpful to know that, most everywhere, you can build on a foundation without a permit - if you know the parameters that govern this option. In Oregon, for example, we can build up to 200 square feet without a building permit for the structure. Check your local building code to see what your options are.


2. “I'm going to build a mobile tiny house on a trailer bed because it's easier.”

I hate to be the guy to burst your bubble, but, this couldn't be further from the truth (whew! That was rough, but I’m a rip off the Band-Aid kind of dude). Building a tiny house is a technically difficult endeavor, as you have to navigate thin walls and tight spaces. At the same time, you have to also include everything that goes into a regular home. A site-built tiny house is more forgiving, as you have thicker walls to work with (typically 6” thick compared to 4” thick on a mobile). Those extra 2” make a world of difference when you are stuffing plumbing, electrical and insulation in there.

Cramped corners become even worse when we shave off valuable inches of wall thickness. Additionally, a mobile tiny house is subjected to an earthquake every time it is moved, which is not an engineering and logistical consideration for a site built tiny house. A mobile has to be lighter, stronger, and weight balanced – these are very difficult design constraints.


3. “A mobile tiny house is less expensive.”

Rarely is this true. A permanent, site-built tiny house can sit on a simple foundation of crushed gravel, which costs about $200 - and that’s with delivery (a bargain, at that). A mobile tiny house demands a heavy-duty, properly sized, and weight-rated trailer, which is easily a $5,000 investment.

Add to that, the need for lightweight and stronger structural components, which typically cost more than heavier materials, and we have a tiny house that can easily cost 3 times as much as a site built home - and that’s before electrical and plumbing go in. So, basically, it’s 3 times more expensive to build a flexible, but dark, and totally dry box (we’re not even going to touch the bathroom situation in one of these un-plumbed monstrosities).

And let’s be real: your time has value (a major consideration that tiny house builders often ignore - at least, at first), and mobile tiny houses, with their many engineering and building challenges, take more time to build.


As you can see, it's common to have a misunderstanding of these basics. I talk to people often who thank me profusely for helping them make their first decision correctly and with all the facts. Truthfully? This is the first of thousands of decisions you’ll have to make along the way. Let How to Build Tiny steer you toward success with every decision you will make in your DIY tiny house build! Contribute to our Kickstarter today and get in on the first round of our training and technical support options!