Cargo Trailer Conversion

Converting a Cargo Trailer into a Travel Trailer – Mold Preventative, Low-Toxin Design

I tried to convert a small cargo trailer into a tiny trailer that can be used for sleeping and living.

In the end, this failed miserably and I would suggest not trying to convert a cargo trailer.

The cargo trailer was a TNT brand DBL ‘A’ 6×12, White, 12″ extra height making it about 7 ft high on the inside.

Side and roof vent (side vents are so small that they bring in very little air. The roof vent can only be wide open if it’s not raining).

RV door lock that locks from the inside (vital) and barn doors that lock from the outside (easier to handle than the ramp door).

You may want to move the lock to the inside when living in it. Front and roof were curved in this one.

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Costs in Canadian Dollars:

• $6100 cost of trailer
• $3600 cost of renos at trailer shop – metal floors, install window, take out plywood (much cheaper, and probably faster if you have the factory do these.)
• $1500 cost of insulation
• Labor for insulation and vapor barrier, foil, and glue – lost track
• $1300 Electrical (+ $185 for CSA inspection and approval – allowing me to legally park the trailer in Canada)

For this price this was a huge mistake, I could have bought a already made, comfortable and non-leaking used trailer for this price. These were 2018 prices.

Necessary Renovations:

Remove plywood.

Installed window – 24 x 30 vinyl awning style to stay open even during the rain.

It’s vertical so that the framing did not need to be cut. I do not find the hard vinyl has a smell but some people would use aluminum.

I installed metal flooring 3/16 hot roll plate steel flooring, 1000 for the metal + welding.

Electrical work

I put in a 30 amp panel with a campground plug and 4 outlets inside.

The electrician wanted a dedicated outlet for the fridge and one for the heater.

Then I had one near the bed for a computer etc, and there is one up high to string up a light and run any kitchen appliances.

If you do attempt such a thing, have these renos done by the factory and not after you buy it.

This was a huge mistake that cost me a lot of money and didn’t save me any time like I thought it would.

Also this is only going to potentially work if you buy one of the models that doesn’t leak. This whole style of cargo trailer I got, which comes in many brands will not work.

And even in that scenario it should not be insulated in most climates.

How long it will take to customize one depends on the brand, the factory, and the time of year.

Add 2-3 weeks on to their estimate.

The back door in mine has structural plywood so that still had to be removed and needed metal reinforcements.

The front end had plywood between the frame and the skin which was a major pain to remove.

Look for a brand that does not have these two issues and you will save a lot of money.

Do the Walls Need Reinforcement?

A big question with cargo trailers is if you need wall reinforcement when you remove the plywood.

There are two answers to this.

The first is that it depends on the brand, some brands will tell you that their trailer is good to go with no plywood, these have thicker frames like the steel CM trailers (that is the only type you should be going with anyway).

Or some companies can customize it with thicker frames. See the pictures below.

The second answer is that the companies might say they are not strong enough but people leave it un-reinforced anyway.

Erik Johnson, me and two other mold avoiders have taken out the plywood and not added anything that would replace it structurally.

Mine started leaking and the company that sold it to me claims that the reason it leaked is that the plywood was taken out and this means there is less stability and it’s easy for pieces to come apart and caulking to come loose. I braced mine since. But it continued to leak and overall be a total disaster.

The picture above is a customized trailer reinforced with aluminum frames. Very robust. If you look closely you can see tape between the frame and the exterior which could be a minor mold risk. But overall this trailer is built way better than the one I tried to fiddle with.

The second picture above is a CM all steel trailer with a robust steel frame, the frame is standard and the company does not recommend reinforcement. This is really the only type you should be going with if you are OK with living in a bare metal box (I do not recommend that level of homelessness when there are so many better options if you can’t live in regular housing).

The third picture above is a standard frame, with plywood removed. Though it’s not reinforced the owner is doing just fine with moving it around frequently. I do know two or three people who pulled this off as a temporary housing.

This picture is my trailer it has the least robust frame of the bunch, while the seller advised that it could be reinforced for longer trips (he told me this after the insulation was up). I then braced/added strapping.

Toxicity of a New Cargo Trailer:

A cargo trailer smells much stronger than someone might anticipate a new metal box to smell.

An extreme mold avoider in a hot climate left it sit for about a year before using.

I have seen two people who have turned around and sold them soon after buying due to the strong smell. Mine was a year old in 2019 and not totally offgassed.

The smell comes mostly from the body of the trailer.

It is a glue smell and may also be from oils on the metal.

There are many other parts that are non-metal (differ slightly between brands) that may include:

Caulk of different types, double-sided tape (you do not want to buy a cargo trailer with tape in the frame – this is a potential mold risk), plastic on the back of the RV door, plastic and glue (very smelly) in the vents to the point that you will likely not be able to use these vents for air, rubber, and foam (glued on) can be found around the RV door, around the barn doors, and possibly around the window on some models, there may be tape holding up wiring, there is the usual plastic coating on the wiring, plastic light and light switch may be included, there may be spray paint on wiring, there may be caps on bolts, screen on top vent, there is also exterior paint which some people have said they are offgassing but I could not pick up a smell on.

In such a small space there are also the tires on the outside to consider – on a hot day you will smell these.

Rustproofing chemicals may also be added to the frame. (Thanks to Madonna Ramp for some of these materials from other brands).

A lot of this can be covered and you can see in mine that it is almost completely sealed up. If you buy one and it smells strong, give it time and/or seal it up like I did mine.

Every trailer takes time to offgas.

Someone was able to get the company Mirage to build without glue or caulk, but she was not able to tolerate the trailer brand new. I would not recommend leaving out glue and caulk, however, that is a bad idea. The whole thing is a bad idea to be honest with the mainstream brands.

Buying a Used Cargo Trailer: 

I did not see any used cargo trailers in my area when I was looking but you can sometimes find these.

Building out the Interior – How Mine was Done (The Second Time)

• XPS Owens Corning Foam 2 inches on walls and floor. 2 inches XPS is R-10.
• The reason I chose XPS is that it has a high R-value and it doesn’t lose its R-value in very cold weather like polyiso does. I also could not find polyiso in my town.
• 1 inch Foil-backed EPS on ceiling (because I needed something thin enough and flexible enough to be curved on the ceiling) (Note: This is backward, there should be more insulation on the roof but I wanted the roof to stay curved and the insulation to stay between the frame so I kept it simple.).
• The brand was R-Tech but I can’t find a link for this. I thought I would add another layer of 1-inch foam if it gets too cold.
• Great Stuff spray foam should be placed behind the foam and on the gaps of the rigid foam (airtight so no moisture gets behind the foam).
• There is one for small gaps and one for larger gaps I needed some of each.
• This then I braced and riveted to the structure which is hard to do in many types of cargo trailers and I would not recommend these standard brands like the one I bought. 
• The insulation did not hold up it went moldy behind it.
• GE 100% silicone for touch-ups to waterproof the exterior

EMFs:

All this metal and foil did not stop wifi or cell phone reception – it lowered my wifi connection only slightly.

If you are concerned about EMFs (electromagnetic fields) consult with an EMF specialist and test out a metal structure before buying.

In theory, it is a Faraday Cage that blocks out some external sources of EMFs and may intensify what is on the inside.

Fixing the leaks

My TNT Mirage Trailer has a number of poorly built aspects. The company took no responsibility for this and the leaks, but of course this is not made or sold to be a living space so I don’t blame them for that.

What has to be fixed on this model or checked on any model: The back doors were leaking, the top sill needed caulking, the door seals were not done right, the doors were bulging at points, bending the doors and adding gaps for leaks. The front diamond plate had nothing behind it, it was a negative lap – a poor design, the front wall should come all the way down. The front plastic cap on the top roof is also a negative lap.

Vertical seams have the ability to let in water in a big storm or when driving it in the rain. Always check windows, doors, and any openings. Screws should be caulked as well. I have seen custom designs with vulnerable roof seams.

Even if you aggressively hose test this before adding insulation and know where the weak points are if you seal up the insulation which you have to do in heating climates this can still leak and you wont see it right away.

These trailers are difficult and I would not attempt insulation in this style/brand again nor recommend it to anyone.

Erik Johnson’s Cargo Trailer:

Erik is the pioneer of cargo trailer living.

He called his trailer and camper MECUs (Mobile Environmental Containment Unit).

Erik used EPS foam without flame retardants. I don’t know how he sourced this but I would think this is the kind used for packing, not insulation. (Apart from packing foam, Schulter boards are the only foam board I know without flame retardants).

In Erik’s trailer, he left a gap (like I did at first) between the foam and the exterior.

He put in weep holes at the bottom in case condensation did find its way to the back. Some trailers like mine come with weep holes.

He has said that there has not been any condensation at the back and he has had this for more than a decade. I put the insulation in front of the frame which created a space naturally behind it (though my floors and ceiling have no space).

This method did not work for me, MAJOR condensation formed behind the walls and I don’t know anyone else that was able to get this to work.

Here is a video of his camper which is done like his cargo.

Other Trailer Options:

I would not build the interior of a cargo trailer. There is just too much that can go wrong to try to build this into a proper camper.

• You could buy a solar kit that is portable that is made for camping.
• If showering in another building, campsite bathroom, or outdoor shower is not an option for you, you could do a bucket shower inside. I did this for a while but it produced so much steam.
• Options for outdoor showers include simple bucket showers, passive solar shower (that one is PVC-free, unlike most of them), active portable hot water shower (this one comes recommended by mold avoiders), or an outdoor tub big enough to bathe in.
• A privacy tent can be used to shower outside or set up a toilet outside.
• You can also DIY and set up something simple like house wrap around 3 trees, or tie a string around 3 trees and the string holds up shower curtains.
• You could install a simple camping or composting toilet inside or use it outside if you need to: some of the options are Luggable Loo, Mini Porta Potty, or Laveo Dry Flush.

Floors

I used these mats on the floor temporarily. They smell like straw.

I also offgassed Marmoleum (takes one month in sun to offgas for me) but I don’t like that there’s a jute backing under the Marmoleum against the metal, that’s a mold risk).

Other flooring options are here.

Heating, Cooling, Lighting, Laundry:

• I planned to mount this silent, energy-efficient, space-saving heater (which smelled at first but did offgas quickly in the sun) with this thermostat. 
• In the summer I planned to use a portable AC.
• I throw them away every fall as they tend to go moldy after one season or two and I have nowhere to store them. 
• I’m used a portable clothes dryer to dry my clothes and I loveed it.
• I used it outside undercover for a while, while I was camping or in the trailer. They work well even in humid and cold outdoor temperatures. I have used this successfully down to freezing. I have not tried it much before freezing but I’m still really happy with it. 

Kitchen:

• I bought a mini fridge which needed a lot of offgassing outside including running it outside.
• I’m used this kitchen island which offgassed fairly quickly but you could use a metal version if you want to avoid wood (and wood sealers and glue). 
• This hanging basket to organize kitchen items 
• I’m using a pressure cooker to cook – you can make almost anything in this.
• If you use it outside, or at least release the steam outside, you will have very little or no added moisture to the trailer.
• You can get away with no other stove, oven, or microwave. You just need an extension cord to use it outside.
• I was going to buy the travel Berkey for drinking water, there is no plumbing in the trailer. Berkey is ideal for well water and water from campsites if you are not buying water. 

Bedding: 

In a high-humidity situation like a trailer, tent, or other camping structure it’s important to have a bed and bedding that will not go moldy.

My bed was up on slats with the Thermarest.

Cotton does not hold up well in high humidity, so I have used more mold-resistant materials:

• Polyester sleeping bag 
• Polyester pillow 
• Polyester pillowcase and sheets (or the one that is made for Thermarest)
• Microfiber towel (no cotton) 
• This heating blanket keeps me warm on very little electricity. If you are worried about EMFs then an infrared heating mat is supposed to be better.
• If you don’t want to use polyester or other synthetics, silk, hemp and wool have better resistance to humidity than cotton and linen.

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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