Category: Daily Updates

Build Notes – Floor, Insulation, and Bathroom Plumbing

Build Notes & Lessons Learned – Floor, Insulation, and Bathroom Plumbing

As I continue refining the design for the cargo trailer conversion, I’m collecting important details that will influence how the trailer is ordered and how the interior systems are built.
These notes focus on floor structure, insulation planning, and bathroom plumbing considerations based on research and reference videos.

No Dovetail for a Level Interior Floor

For this build, a flat, level floor is essential. This means the trailer must be ordered with no dovetail.
A dovetail is the angled drop at the rear of many cargo trailers, designed for loading low vehicles.
While useful for ramps, it creates an uneven interior floor and complicates cabinetry, flooring, and bathroom layout.

Choosing a non-dovetail rear ensures:

  • A fully level floor from front to back
  • Simpler installation of flooring, insulation, and cabinetry
  • Better support for the raised shower platform and tank placement

Interior Doors Must Be Raised for Floor Insulation

If the trailer does not come factory-insulated, the interior floor will be built up with insulation and subfloor layers.
This adds approximately 1.5 inches of height to the finished floor.

To avoid clearance issues:

  • Interior doors (bathroom, bedroom, etc.) must be raised at least 1.5″ during installation.
  • Dealers should not install interior trim — trim should be left loose inside the trailer.

This prevents the door from dragging on the finished floor and allows trim to be installed after insulation and flooring are complete.

Backer Boards Before Insulation (Video Reference)

In this video (timestamp 2:15):

Cargo Trailer Conversion – Insulation Prep

The creator explains the purpose of installing backer boards before adding insulation.
These boards provide:

  • A solid mounting surface for walls and fixtures
  • Structural support for areas where screws cannot bite into foam
  • Better rigidity and long-term durability

This reinforces the plan to include backer boards in key areas before insulating the walls and ceiling.

Urine Separator Plumbing Into Sump Pump (Video Reference)

In this video (timestamp 27:50):

Cargo Trailer Bathroom Plumbing – Urine Separator & Sump Pump

The builder demonstrates how the urine separator line from a composting toilet can be routed into the same shower sump pump box that feeds the gray tank.
This setup includes:

  • A dedicated urine drain line entering the sump box
  • A check valve to prevent backflow from the gray tank
  • Automatic pumping of both shower water and urine into the gray tank

This is a useful reference for integrating the composting toilet’s liquid output into the interior gray tank system without needing a separate container.

Summary

These notes help shape several key decisions for the build:

  • Order the trailer without a dovetail for a level interior floor.
  • Ensure interior doors are raised 1.5″ if insulating the floor after delivery.
  • Use backer boards before insulation for structural support.
  • Consider routing the urine separator into the sump pump with a check valve.

These insights will be incorporated into the final layout and construction plan as the build progresses.

Rethinking the Nature’s Head: My Composting Toilet Deep Dive

Rethinking the Nature’s Head: My Composting Toilet Deep Dive

When I first started planning this build, the toilet decision felt “done.” I picked the Nature’s Head, dropped it into the plans, and moved on.
It’s a proven, popular composting toilet with a solid track record, and it slotted neatly into the bathroom layout without much debate.

But as this project has evolved, so has my thinking. Today was one of those days where I went down a deep rabbit hole on composting toilets—especially the DIY side—and came back up seriously questioning whether a $1,000+ commercial unit still makes sense for this build.

What a Composting Toilet Really Is

The more I read, the more I realized how simple the core system really is. Strip away the marketing and molded housings, and a composting toilet is basically:

  • A solids container for the composting material and waste
  • A liquids diverter to keep urine separate
  • A small ventilation system to move air and control odor

That’s the heart of it. Everything else is enclosure, ergonomics, and branding.

Nature’s Head does all of that in a clean, integrated package—and it does it well. But once you understand the underlying components, it’s hard not to look at that four-figure price tag and start doing the math.

I’m Not Above Building My Own

One thing about this build: I’m not afraid to get hands-on. I’m already designing and installing plumbing, electrical, propane, and HVAC systems.
So when I look at a composting toilet and realize it’s mostly smart carpentry plus a few key parts, the thought naturally pops up:

“I can build something just as functional for a fraction of the cost.”

And at this point, I really believe that.

The Nature’s Head is still a great product. It’s well-engineered, well-documented, and widely used. But $1,000+ (once you factor in tax and shipping) is a big chunk of budget for something I might be able to replicate for a couple hundred dollars and a weekend of focused work.

DIY Composting Toilet Kits Are Everywhere

Once you start looking, you realize there’s an entire ecosystem around DIY composting toilets:

  • Urine diverters you can buy as standalone components
  • 12V vent fans designed specifically for composting setups
  • Complete “guts only” kits that let you build your own enclosure

That last one is especially interesting: I can build a custom enclosure that fits my space, my height, my storage needs, and my aesthetic—without paying for a pre-molded shell that was designed for a generic use case.

In other words, I can design the toilet to fit the trailer, not force the trailer to fit the toilet.

Ventilation: The Real Key (And the Easy Part)

The more I read, the more one theme kept coming up: ventilation is what makes or breaks a composting toilet.

If you have:

  • A sealed solids chamber
  • A properly sized vent line
  • A small, reliable 12V fan pulling air out

…then odor control becomes very manageable. And those are all things I’m already dealing with in other parts of the build—fans, vents, penetrations, and airflow.

So from a systems perspective, a DIY composting toilet doesn’t feel like a stretch. It feels like one more small subsystem that plugs into the larger ventilation and electrical picture.

Where I’m At Right Now

On paper, the Nature’s Head is still the “official” toilet in my plans. It’s in the diagrams, it’s in the layouts, and it’s in the documentation.
But mentally, I’m in a different place now.

I’m keeping my options open. I’m not locked into a commercial unit just because I wrote it down early in the process.
As the build progresses and I get deeper into the details, the idea of a custom composting toilet—built around my space, my needs, and my budget—is becoming more realistic and more appealing.

The Takeaway for Today

Today wasn’t about buying anything or installing anything. It was about stepping back and asking a simple question:

“Does this expensive, off-the-shelf solution still make sense now that I understand how it works?”

Right now, my honest answer is: maybe not.

I’m not making a final call yet, but I’m also not blindly paying $1,000+ for something I can likely build myself for a fraction of that cost.
This build has always been about intentional choices, and the toilet is officially back on the “intentional choice” list.

For now, I’m going to keep researching DIY composting designs, sketching ideas, and watching how the rest of the systems come together.
When it’s time to commit, I want that decision to feel as solid as the rest of the trailer—not just “good enough,” but truly aligned with how I’m building this thing: thoughtfully, creatively, and on purpose.