When building anything, the end result will only be as good as the foundation it was built on. Nothing can be more true and crucial for a tiny home. Some people decide to build their tiny homes on a solid foundation, or skids, but most will end up building on a trailer for various reasons.

Our latest build is on a custom trailer built locally by Trailer Made. As a disclaimer - We’re making this endorsement of Trailer Made tiny house trailers on our own accord, without any request from Trailer Made Custom Trailers, LLC. We’ve built on equipment trailers in the past, but decided to move to a trailer built specifically for tiny homes and we can say that we’ll never go back to building on anything else again! These trailers are built rock-solid and provide you many benefits over buying a different trailer.

 

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If you’ve received a tiny house trailer and you’re ready to get started on your build, it’s critical that you take the time to complete all necessary steps here in the right order. By the time your subfloor is done, you need to be sure of a few things.

1. Your subfloor needs to be able to breathe.
2. Your subfloor needs to be insulated.
3. Your subfloor sheathing needs to be sturdy, installed correctly and secured to the trailer.

 

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Steps to build your subfloor & foundation

Before you get started, get your materials together. We generally use a combination of rigid foam insulation and canned/spray-foam insulation in the subfloor. We also use a sill sealer to prevent some thermal bridging from the metal framing of the trailer. We only use Advantech subfloor sheathing, and since this is being attached to metal framing on a trailer, we also use 2” self-tapping metal screws.

Step 1 - Insulate the subfloor.

We measure the depth of the trailer cavity, as well as the width between the metal framing. In our case, the trailer has a 3” depth, and 14” widths throughout most of the trailer, and a length of 80” between the metal framing as well.

When you’ve got these measurements, start cutting down your rigid foam insulation so that it will snugly fit into these areas. It’s important that you use more than one piece of foam insulation in each cavity to get to the full 3” depth. The reason for this is that you can use the vapor barrier of the foam insulation on both the top and bottom of the cavity.

After you’ve got the floor completely insulated, fill any gaps or cracks with canned foam insulation. This is a very important step!

Step 2 - Insulate the metal framing.

Using sill sealer and some construction adhesive, cover each metal framing stud of the trailer with this foam padding. This will not remove all thermal bridging, but it will help significantly.

Step 3 - Sheath the floor.

As I mentioned before, we only use Advantech flooring. There are several reasons for this, but the main reason is that this engineered flooring is exceptionally water resistant. During construction, your floor WILL get wet, and Advantech flooring will not suffer any negative effects from this. You can read more about AdvanTech flooring here

You may be tempted to lay the flooring across the 8ft of the trailer, and just work your way from the front to the back of the trailer (or vice-versa), but you must avoid doing this. Subflooring is designed (and much more sturdy) when it’s installed perpendicular to the floor studs/joists of the trailer. Staggering the seams of the flooring is another good idea, but with such a small space and such an incredibly strong foundation, we generally skip this.

Lay your flooring down and get it as flush to the trailer flange as you can. Be sure that you only secure the flooring with 2-3 self-tapping metal screws before you move on. You want to be sure that your last subfloor sheathing is as straight as the first, and if you take the time to put 20+ screws in the sheathing as you go, there’s a chance you’ll regret it when you get to the end!

This flooring is tongue and groove, and will automatically create the appropriate gap/spacing for you to do the installation.

Step 4 - Screw it down!

Lastly, once your subfloor is all down, you’re going to spend the next 1-2 hours screwing it down permanently. Advantech flooring has visual guides that show you where you need to attach the flooring. A good rule of thumb is to screw every 6-8 inches on the outer edges of the sheathing, and every 12 inches on the inside of the sheathing (Again, just follow the visual guide!).

 

Now…. you’re ready to move onto building some walls!

 

Do you have any ideas on how to improve a tiny house foundation or subfloor? Do you have any thoughts or experience from building your own? Share your thoughts with us!

 

1. Remember to be road legal.

You want to be sure that the end result of your tiny house build is one that you can legally tow down the road without incurring any trouble or extra costs on the way. This means you should be no more than 8’6″ wide, and 13’6″ tall from the road to the very top of the roof.

The height is ultimately the most tricky part to get correct. You need to take into account the height of the trailer, your wall framing, the extra height of your roof pitch, the roof sheathing and lastly, the final roofing material (metal roofing, etc).

2. Get your materials in the right order.

You want to make sure that you’ve acquired your materials in the right order, so you can minimize any delay in your build. Once you’ve decided on a building style/design/plan, you want to get your materials.

First, order your trailer (or find your trailer, but we recommend buying a new trailer built and designed for a tiny home! Try these guys out at trailer made - they’re the best!).

Next, order your windows. Depending on how quick you can frame your home, another long delay can be windows. You may find that you’re waiting as many as 6 weeks for a custom window order! (we’ve never had this kind of delay, but we’ve heard horror stories!).

Next, order all of your lumber and sheathing. If things work out, you’ll have a dried-in structure and very little to zero waiting time for materials!

3. Plan for the weather.
If you’re going to be building outside, you should plan for weather. Get tarps, and plan accordingly. If you know rain is coming in the afternoon, wake up early and knock out as much as you can! It’s best to frame walls and leave them covered or in a dry area until you’re able to find the time to get everything stood up and sheathed in a dry time.

Another option here is to use water-resistant materials. We always use high quality, water-resistant materials where possible. This means that we don’t have to worry much about the rain if an unexpected storm pops up and we’ve got a tiny home sitting out in the elements!

4. Source your reclaimed windows FIRST!!!

If you plan on using reclaimed windows and you’re trying to source them from a local shop, or craigslist, be sure to do this before anything else. If you have already framed your tiny house, then you are most likely stuck with finding windows that will fit inside those framed openings. Getting your reclaimed windows first means that you can make little tweaks to window openings to make sure this process goes smoothly, and much faster!

5. Get Started!

Stop thinking about doing this, and do it. I had a friend many years ago that would frequently say “Ain’t nothing to it, but to do it”. Nothing could be more true. If you want to build a tiny home, or buy a shell and finish the rest yourself, then do it already! Get financing if you need to, or look into other options (We offer in-house financing!) and make your dream a reality.

What is a “gotcha” that you’ve thought of or come across when it comes to building or buying a tiny home? Have you ever found a great resource for materials or reclaimed materials?