Building a Tiny House When Chemically Sensitive – What to Consider

Some preliminary considerations if building a tiny home with healthy materials:

1. Choosing Plans

Because I wanted a more modern style, I bought conventional plans from Leaf House.

I wanted to change the layout to make the living room bigger, which entailed changing almost every other aspect of the design.

In a tiny house, one change in the floor plans can change everything.

This ends up costing a lot more not just in time spent redrawing plans, but in recalculating all the supplies: lumber, the electrical system, the plumbing system, (custom) window sizes, etc.

A lot of time (months) was spent calculating and ordering supplies. A week was probably spent on window placement and sizes alone.

In order to reduce costs, you might want to start with pre-fab window sizes and design around that.

But it’s way more efficient cost-wise to buy plans that are almost exactly how you want things to look.

Changing to non-toxic materials may demand changes to the plans such as changes to the framing in the flooring, changes to the thickness of the walls, ceiling, and floors (since insulation might be thicker), and changes to the weight.

It is possible to build a non-toxic tiny home without changing anything substantial if you use plywood and standard-thickness insulation.

Be careful when buying plans, the technical aspects are almost certainly not going to be up to scruff in terms of mold prevention.

You will need an architect or designer with building science knowledge to review the design and moisture management system.

2. A Builder who Understands Chemical Sensitivities

I now recommend going with someone local and someone very skilled.

I would prefer a skilled builder over a “green builder”.

The best way to go about this is to create a complete materials list in one-on-one consultations and then present that to a builder.

This way they have a clear guideline of what you want to use and don’t want to use and they can give you an accurate quote on the cost, time, and if they are willing to take this on.

If you don’t have your list organised you will need to spend a lot more of the builder’s time, they will almost certainly get frustrated with you, likely have to charge more and the relationship can break down.

I don’t recommend any specific builders for tiny homes on wheels, but I go over a few companies I would be wary of and what to look for in Substack.

3. Trailer Weight

A big SNAFU was that the plans we bought were designed for a trailer rated at 10,000 lbs.

If using MgO board or solid wood instead of plywood, that is heavier that drywall and plywood; MgO siding or HardiePlank is heavier than wood siding; cotton and wool are heavier than foam insulation; and tiles or hardwood are heavier than vinyl or laminate flooring.

A composting toilet is also fairly heavy.

Those have to be considered before buying the trailer.

4. Metal v. Wood

Metal framing is very prone to condensation.

Unless you are building with metal SIPs, metal framing is not a good idea.

There is a metal SIPs tiny house on wheels I recommend in the tiny home series in Substack.

5. Mobile Home v. Travel Trailer Registration

This was one of the most confusing aspects of the build.

Regulations vary from Province to Province and from State to State as well.

In BC to get your house registered as a mobile home you have to have it built by a certified mobile home builder.

Not getting mobile home certification means not being able to park and live at a mobile home park which is unfortunate.

If you can’t tow it legally it is way harder to move a tiny house.

Some tiny houses have RVIA certification which gives you more flexibility with living in RV parks. However, some of the requirements may conflict with building a mold safe home.

With this you can get house insurance as a mobile home or as a travel trailer or RV.

If you are having someone in the US build it and importing to Canada it has to be RVIA certified.

6. Choosing Materials

Choose the materials before you start with your builder.

Factor in time to order samples and test materials for your own sensitivities.

If you get reactive easily, this will be a long and protracted stage as you find out what you can’t tolerate by having reactions over and over. There needs to be time for recovery between testing.

It was a happy mistake that the finishing was left to me after delivery.

The testing of wood stains/sealers/paints/tiles/tile sealers/shower materials has been a very long process and it has been much easier to do this slowly over time.

I also became more hypersensitive due to avoidance once moving into my tiny house: materials that I didn’t react to when testing but then did include: cotton batt insulation (if you react to new clothing you will likely react to that), MgO board (I am on the fence about it – a few extremely sensitive people have said there is a slight reaction to it) and I have become much more sensitive to all paints and wood glues.

I provide consultation services to help people navigate this complicated process of choosing materials.

7. Time to Off-gas

Many materials and appliances will need to off-gas before use.

I didn’t do that well in my house for the first couple months, so I would say even with the best materials there is wiring, there is plumbing and plumbing glue, there is wood glue, there will be some silicone – these all need some time to off-gas.

We left the appliances running for a month before use.

I was lucky that I could move in immediately and left the window open for the first few weeks.

Some people need a year to off-gas a new house, even when every material was carefully selected.

It’s essential to be clear of mold and to work on rewiring the brain in order to not spend a year unable to move in (or worse, never being able to move in which has happened to people I know).

8. Where to Park it

Many tiny homes are off the grid and use propane to power most systems, which is not an option for most MCS clients.

Propane may be suitable for hot water heating, refrigeration and heat/AC, but the power for your stove/oven, compost toilet, lights, fans, etc will need to be electric for most people.

Solar panels on the roof would only cover a small portion of the electrical.

It is not possible to have a tiny house certified as a mobile home where I live, which excludes the possibility of parking at a mobile home park.

It may be possible to park at an RV park if your electrical load is 60 amps or less and you have the proper plug for an RV park. You will also need RV sewage hookups.

Having a tiny home certified by RVIA can have benefits in allowing you access to more RV parks. In many rural places, you can have a tiny home on your own land, either legally or “just squatting”, set up with electricity and water.

Separate posts on tiny house systems, composting toilet and greywater, custom non-toxic shower…

Corinne Segura is an InterNACHI-certified Healthy Homes Inspector with certifications in Building Biology, Healthier Materials and Sustainable Buildings, and more. She has 10 years of experience helping others create healthy homes. You can book a consult here.

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