Building A Tiny House On A Foundation – What You Need To Know Before You Build

building a tiny house on a foundation
When I built my own tiny home, I hadn’t really considered building a tiny house on a foundation. But in recent years, more and more people are skipping the trailer and building a tiny house on a foundation.

I get a lot of questions about what it costs to build a tiny house on a foundation, what the legal rules are around building codes, and why you might not want to consider this option.

Can You Build A Tiny House On A Foundation?

Can You Build A Tiny House On A Foundation

Absolutely! A tiny house can be built on a trailer or on a traditional foundation. You could even have a basement if you wanted.

When you start building your future tiny house, you’ll need some type of supporting structure to rest the house on and build off of. There are several types of tiny house foundation options that you can consider for your build. Each of these foundation types has pros and cons, but all will be able to support your tiny home.

Slab Foundation

tiny house slab foundation

A slab foundation is a simple pad made by first creating a wood frame called a form. Then you fill the form frame with concrete to form a slab. In some instances, you’ll lay in rebar or wire mesh to reinforce the pad, but that isn’t always necessary. Typically, 4-6 inches thick is all you’ll need to start building your tiny house, just make sure you pre-plan any drain lines.

PROS

  • Sturdy foundation
  • Relatively affordable
  • Simple to build

CONS

  • Have to preplan drains
  • Lacks flexibility in future
  • No access to run wires/lines

Vented Crawl Space

tiny house with a vented crawl space

A vented crawl space is formed by short walls that you build your house on. Typically, footers are poured around the edge of your foundation and walls are built on those about 2-3 feet tall. This works great because you can run all your wires and plumbing in this crawl space and if there is ever an issue, you can crawl under your home to get access to fix them. Your crawl space walls will have some vents in them to allow for moisture to vent out of. The downside is these places are typically dark, dirty and can lead to moisture issues.

PROS

  • Sturdy foundation
  • Still pretty inexpensive
  • Access to wires/plumbing

CONS

  • More expensive than slabs
  • Moisture can lead to mold
  • Requires steps up into your house

Sealed Crawl Spaces

sealed crawl space under a tiny house

A sealed crawl space is basically a mini basement in your tiny house. It differs from a vented crawl space in the fact that instead of being open to the outside environment via vents, you seal it off and condition the space as part of your building envelope. This is my preferred method because we cut down on potential moisture issues, keep bugs out (mostly), and can use the space for storage! Typically, these will be built using the same walls that surround the outside, but then a floor is poured in after. Make sure your contractor insulates and installs a vapor barrier!

PROS

  • Extra storage
  • Access to wires/plumbing
  • Controls bugs and moisture

CONS

  • More expensive
  • Newer approach
  • Requires HVAC

how to build a tiny house

Full Basement

tiny house with a full basement

This is the most expensive option, as you’ll be building down into the earth which requires engineering. The additional square footage gained for storage or additional living space is usually very affordable, but brings with it additional hoops to jump through. Make sure you check with local codes about egress and ensure you have a contractor that properly drains, seals and insulates the basement.

PROS

  • Extra storage
  • Access to wires/plumbing
  • Low cost square footage

CONS

  • Most expensive
  • Requires permits
  • Requires engineering

Skids or Runners

tiny house on runners

This is an option that serves as foundation, but also is somewhat mobile. These are simply large timbers placed on the bottom of the house that act as runners to drag the house along on. These are usually lumber, or sometimes steel, which can give you the best of both worlds.

PROS

  • Mobile in a pinch
  • Low cost option
  • Simple materials

CONS

  • Hard to pass code
  • Can rot away
  • Hard to access under house

Piers or Tubes

tiny house built on piers or tubes

The last type is a footing placed in a grid pattern into the ground with a bracket on top that connects to the under frame of your house. These piers will be laid out in a grid with large timbers running between them to form the sub floor framing of your house. They’re ideal for slopped lots and can be a great option for DIYers.

PROS

  • Affordable
  • Access to wires/plumbing
  • Easy for a DIYer

CONS

  • Requires permits
  • Not always allowed
  • Not an enclosed foundation

Cost To Build A Tiny House On A Foundation

cost to build a tiny house on a foundation

One of the larger costs associated with a tiny house on wheels is the trailer, costing between $3,000 and $6,000 for the trailer alone. A simple slab might only cost you $1,000-$2,000 including labor. So right off the bat you’ll be saving a pretty good chunk of change skipping the trailer.

That said, you’ll have to make sure you’re complying with all codes, because if things go poorly with the city, you can’t just pick up and leave. Permits to build a house vary based on your location, but nationally you’re looking at an average of $1,200 for all your permits to build your house. Add to this that they’ll most likely require you to have a water line and sewer connection, which is always expensive. My city charges a whopping $11,582 for this!

how much does a tiny house cost

If you live in rural locations or out of the main lines of your city, you’ll need to drill a well and install a septic system. Read more here about how I did this on my land.

Many people, myself included, were pushed into off-grid options like a composting toilet and solar power because they’re a bit more affordable. The best part is, after the initial cost, you don’t have any bills to pay. Being pushed to more affordable options like this meant I had to step outside building codes and thus become an illegal dwelling, which then lead me to choose a trailer, so I could move if I needed to.

You can see that while you’ll save some money on the trailer, you’ll have to spend a lot more to comply with building codes and local regulations. After that, building the house will be about the same for the rest of the details.

Pros and Cons of Building A Tiny House On A Foundation

Pros and Cons of Building A Tiny House On A Foundation

There is a lot to consider when it comes to building on a trailer versus building on a foundation. Tiny houses have been traditionally built on a trailer, but that doesn’t mean they have to be. Here are some of the pros and cons of building a tiny house on a foundation:

PROS

  • Can build larger than a trailer footprint
  • Can build different shape then a trailer form factor
  • Can allow for access to under house utilities
  • Increased insulation potential under house
  • Basements and sealed crawl spaces used as storage
  • Allows for future expansion and flexibility
  • More legally accepted

CONS

  • Additional costs to build
  • More sturdy and permanent than trailer
  • You’ll need to pay taxes on the house
  • Slabs prevent under house access
  • Incurs additional red tape costs
  • Requires permits and engineering
  • Not mobile

How Do You Build A Tiny House On A Foundation?

How Do You Build A Tiny House On A Foundation

The main connection between the walls of the house and the foundation are built off of a pressure treated sill plate, which is just a 2×4 or 2×6 laid on it’s wide side. Between the top of the foundation and sill plate, you want to use a gasket to act as a capillary break between the concrete and the wood, seal the joint for air and prevent bugs from getting in. I usually recommend using a foam gasket with some contiguous beads of acoustical caulking because it will make sure that the connection is always sealed tightly.

tiny house foundation drawing
how to build a tiny house

You’re going to need to anchor the sill plate to the foundation itself with anchor bolts. Sometimes these are laid at the time of pouring, other times people drill holes and add them after. Your local code enforcement will have very specific requirements on the type, spacing, fasteners, and more, so check with them first.

Once you have your sill plate installed, sealed, and anchored, you then use that as your bottom plate of your wall framing. Consider how you’re going to run your floor joists when you pour your foundation — a good contractor will help you work out all the details on this front. Below is a great diagram of this process. If you like these details, my book, “How To Build A Tiny House” is loaded with these, including 160 custom diagrams with details like this.

 

Tiny House On A Foundation Design Ideas & Photos

Tiny House On A Foundation Design Ideas

Here are some great tiny houses built on foundations that can help you get some inspiration for your own home. Keep in mind that your local municipality will have specifics on building codes concerning details, building methods and sizes that you’ll need to comply with.

Orcas Island Cabin

Orcas Island Cabin

This is a dream cabin of only 400 square feet built by Vandervort Architects that I’d love to stay in myself. A simple house with rich woods on an island in the Pacific Northwest.

Orcas Island Cabin view
Orcas Island Cabin interior
Orcas Island Cabin exterior
Orcas Island Cabin plan

Escape Cabin

This one is a personal favorite because of the large screened porch and the smart bedroom layout. This small house on a foundation is around 400 square feet and is built on a steel frame, so it can be transported in a pinch. Check out this house and others from Escape.

tiny house escape cabin
escape cabin kitchen
living area in escape cabin
esacpe cabin bedroom

Muji Hut

muji hut

I have personally thought about building one of these on my land — the simple design is super minimalistic while still having a lot of functionality. A simple room with a bed and a heater is all you need for a weekend getaway. I figured I could have some hidden storage in one of the walls and a simple outdoor shower off the back.

muji hut exterior
simplicity of a muji hut
modern design muji hut
muji hut interior

The Rocker

the rocker

This was designed by Viva Collective with an innovative L-shape that allowed for a great deck to be added. This goes to show that you don’t need to be confined by a trailer and the results can be stunning!

the rocker tiny house
the rocker interior
bathroom in the rocker house
the rocker tiny house bedroom

Shipping Container Trio House

shipping container trio house

This is an interesting shipping container home that is made up of three different containers. Shipping container homes are growing in popularity as an affordable home option. They can be had for a few thousand dollars and provide most of the structure of the home.

shipping container trio exterior
shipping container house kitchen
shipping container bedroom
shipping container living area

Should You build A Tiny House On A Foundation?

Should You build A Tiny House On A Foundation

In the end, I think you need to decide if you’re willing to jump through all the hoops and deal with the red tape of building on a foundation. Having a legal house is peace of mind, but that comes at a cost of extra permits and requirements. Many people opt for a trailer because it skirts most of those issues and costs, but for those who want a tiny house outside the normal trailer footprint, a tiny house on a foundation is a great option.

Your Turn!

  • Trailer or foundation, which do you choose?
4 Comments
  1. What are your thoughts on collecting rainwater to be used, certainly cheaper than drilling a well I’m guessing, I saw a video of a guy installing tiny gutters (for lack of a better term) around the van so that when it rains, he is funneled down, inside van and stored in his water tank. So cool

  2. This was a great article… I saved the web link in my collections section for later reference. The graphic on the foundation pieces really was good for me as I have no idea what a real foundation involves… I have always wanted the extra insulation from 2×6 boarding. I am a fan of “SMALL ON A FOUNDATION” for myself and those with roots or homeless populations. I think the main advantage of a Tiny House is mobility… to take your housing (comforts of home) with you wherever you go. I think they would make great guest housing as well. I was so impressed with a few of the design illustrations… the tall bed with lots of storage below, the house with the huge screened porch, and more. I hope to see more of these types of articles.

  3. Behind my “real” garage, I have a slab from an old garage — 12 x 16′ with a 6″x6″ footer around the three sides that aren’t where the door was — and I’ve thought of making a building on that.
    The advantage is that I could use the main house’s plumbing (like a sort of reverse outhouse) and wi-fi, and I could probably run a heavy extension cord from my 100A “real” garage. I’d use the Tiny only when I had friends over, or let their kids camp out in the playhouse.
    Ultimately, I could add a composting or incinerating toilet, a cold-water tank and wash basin that would drain into the bushes, and a proper electrical hookup, and make a year-round, real Tiny.
    It would be more a play house or man-cave or something than a real dwelling. I know I’ll have some questions from the city, but if all I’m really building is a kinda nice shed…
    Too crazy?

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