Emery Custom Builds

Common Van Conversion Mistakes

We've built enough vans to see every mistake in the book. Here are the ones that cost the most time, money, and frustration — and how to avoid each one.

The most expensive van conversion mistakes are undersized electrical systems, wrong insulation choices, and poor exterior sealing -- each can cost $2,000-$10,000+ to fix after the build is finished. Other common problems include water system undersizing, ignoring ventilation, and skipping maintenance access panels. Emery Custom Builds sees these mistakes regularly at our San Diego shop, both in builds we're hired to fix and in conversations with owners who learned the hard way.

Every van conversion has decisions that are hard to undo once you've committed. Cut a hole in the wrong spot, undersize your electrical, skip insulation in the wrong area — and you're either living with it or tearing things apart to fix it.

We see these mistakes constantly at our San Diego shop, both in builds we're hired to fix and in conversations with owners who learned the hard way. This guide covers the most common ones, with practical advice on how to get each one right the first time. Whether you're building yourself or hiring a shop, knowing what to watch for makes a real difference.

How Big Does My Van Electrical System Need to Be?

This is the most expensive mistake in van building. People underestimate how much power they actually use, buy a battery bank and solar setup that's too small, then spend their first trip rationing electricity or running to campgrounds for shore power.

The fix is straightforward: calculate your actual daily power draw before you buy anything. Add up every device — fridge, lights, fan, water pump, phone and laptop charging, heater. Total the amp-hours. Then size your battery bank at 1.5–2x that number and your solar system to match.

We see builds come in where someone bought a single 100Ah battery for a full-time rig. That's maybe one day of power with moderate use. A proper full-time system usually needs 200–400Ah of lithium and 400–600 watts of solar. It's more upfront, but it's the foundation of everything else working.

What Insulation Mistakes Should I Avoid in a Van?

Insulation is one of those things that's nearly impossible to change once the interior is built. Choose wrong, and you're dealing with condensation, mold, and poor temperature regulation for the life of the van.

We use 3M Thinsulate for walls and ceilings. It handles moisture well, doesn't compress over time, fills irregular van cavities, and has excellent thermal performance for its thickness. For floors, XPS rigid foam board gives you the R-value and compression resistance you need under subfloor.

Common insulation mistakes we see:

  • Fiberglass batts: They absorb moisture, sag over time, and lose R-value when compressed into irregular van wall shapes.
  • Spray foam everywhere: Spray foam bonds permanently to the van body. If you ever need to access wiring or fix rust behind the walls, you're grinding it out. It also makes the van nearly impossible to resell as a cargo van.
  • Skipping floor insulation: The floor is a massive thermal bridge. Without XPS foam or similar rigid insulation, cold radiates up through the floor in winter.
  • Gaps and voids: Every gap in insulation is a cold spot where condensation will form. Fill every cavity completely.

How Much Water Storage Do I Actually Need in a Van?

People consistently underestimate how much water they use. A quick shower uses 2–3 gallons. Washing dishes, another gallon or two. Drinking, cooking, hand washing — it adds up fast. A 20-gallon tank sounds like plenty until you're on day two of a five-day trip and already rationing.

We recommend sizing your freshwater system for at least 3–5 days of independent use. For most couples, that means 30–45 gallons of fresh water and a matching grey water tank. Full-time travelers often run larger.

Also plan your grey water capacity to match your freshwater. If you can carry 40 gallons of fresh but only hold 20 gallons of grey, you'll have to dump grey twice as often — and finding dump stations is often harder than finding water fill-ups.

What Kitchen Layout Mistakes Should I Avoid?

The kitchen is the most used area in a van. Get the layout wrong and you'll feel it every meal. Common problems:

  • Cooktop too close to the wall: No room for pot handles, heat damage to adjacent surfaces, and a fire risk with curtains or fabric nearby.
  • Fridge in a dead corner: If you can't open the fridge without contorting around furniture, you'll hate it daily.
  • No counter space: You need at least some prep area next to the cooktop. Even 12 inches makes a difference.
  • Ignoring weight distribution: Heavy items (water tanks, fridge, battery bank) should be low and centered. A top-heavy van with all the weight on one side handles poorly on the road.

Spend time with cardboard mockups before you commit to a layout. Sit in the van, pretend to cook, pretend to sleep, pretend to work. Walk through your daily routine in the space.

How Do I Prevent Condensation and Mold in My Van?

Two people sleeping in a van produce about a liter of moisture overnight just from breathing. Add cooking, wet gear, and showering, and you've got a condensation problem that will destroy your build from the inside out if you don't manage it.

A quality roof vent fan (like a MaxxFan or Fan-Tastic) is non-negotiable. It pulls moist air out while drawing fresh air in. We install these on every build, and they run almost 24/7 in humid climates or cold weather.

Beyond the fan, think about airflow paths through the van. Crack a window on the opposite end from the fan to create cross-ventilation. Keep air moving behind wall panels where condensation likes to hide. And don't seal the van up completely — you want controlled airflow, not a sealed box.

How Do I Keep Van Plumbing from Freezing?

If you ever plan to use your van in cold weather — and most people end up in cold weather eventually, even if they didn't plan on it — your plumbing needs to survive freezing temperatures.

The most vulnerable points are external tanks, exposed water lines in the floor or undercarriage, and the water pump. A burst water line inside a van means water soaking into subfloor, insulation, and cabinetry — potentially thousands in damage.

What we do on builds:

  • Insulate all water lines, especially any runs near the floor or exterior walls
  • Keep tanks inside the heated space whenever possible
  • Install low-point drains for winterizing
  • Use PEX fittings that have some freeze tolerance (though they're not freeze-proof)
  • For external tanks, consider a tank heater pad for cold-weather use

How Much Storage Do I Need in a Van Conversion?

People design beautiful open layouts and then have nowhere to put anything. Clothes, food, tools, outdoor gear, toiletries, electronics, cooking equipment — it all needs a home. If it doesn't have a dedicated spot, it ends up on the bed or the floor.

Design storage into every decision:

  • Under-bed garage: The single biggest storage area in most builds. Size the bed height to maximize it.
  • Overhead cabinets: Use all available wall space above the kitchen and living area.
  • Door pockets and cubbies: Small items need small dedicated spots.
  • Seat bases: If you have a dinette or bench seat, make the base hollow with a lift-up top.
  • Vertical space: Hanging organizers, hooks, magnetic strips for knives, bungee nets for light items.

What Happens If I Don't Seal My Van Roof Properly?

Every hole you drill in the roof or body of the van is a potential leak. Roof fans, solar panel mounts, antennas, cable entry points, shore power inlets — each one needs to be sealed properly the first time.

Use the right sealant for the job. Dicor self-leveling lap sealant is the standard for horizontal roof surfaces. Butyl tape works well under trim pieces and flanges. Silicone sealant is fine for some applications but doesn't adhere to all surfaces.

Check your seals at least once a year. UV and temperature cycling break down sealants over time. A five-minute inspection can catch a failing seal before it becomes a water damage repair.

What Electrical Safety Rules Should I Follow in a Van?

Electrical fires in a van are fast and devastating. There's no room for error, and there's no fire department arriving in 3 minutes when you're parked in the middle of nowhere.

The rules are straightforward:

  • Fuse every circuit. Every positive wire leaving the battery bank or distribution panel needs a fuse rated for the wire gauge.
  • Use correct wire gauges. Undersized wire overheats under load. Look up the ampacity charts and don't guess.
  • Crimp, don't twist. Use proper crimp connectors with a ratcheting crimper. Twist-and-tape connections vibrate loose in a moving vehicle.
  • Separate AC and DC wiring. Never run 120V AC and 12V DC in the same conduit or bundle.
  • Label everything. Every wire, every fuse, every breaker. When something goes wrong at 10 PM in a parking lot, you need to find the right circuit fast.

For a full walkthrough of van electrical systems, see our electrical hub.

Why Do I Need Maintenance Access Panels in My Van?

Everything in a van will eventually need service. Water pumps fail. Fittings loosen. Wiring connections corrode. If you've built over all your access points, a 20-minute repair becomes a full-day teardown.

Build access panels into your design from day one. You need to be able to reach:

  • The water pump and all plumbing connections
  • Battery bank and electrical distribution
  • Water tanks (both fill points and low-point drains)
  • The back side of the water heater
  • Any shut-off valves or breakers

Removable panels with magnetic catches or quarter-turn fasteners give you quick access without tools. It's a small detail in the design phase but a massive difference when something needs attention on the road.

Should I Document Everything During My Van Build?

Take photos of everything before you close it up. Wiring runs behind walls. Plumbing connections under the floor. Insulation coverage. Structural modifications. All of it.

Create a wiring diagram that shows every circuit, fuse size, and wire gauge. Write down your plumbing layout including tank locations, drain points, and valve positions. Keep a list of every component — brand, model, where you bought it, and any warranty info.

This documentation is invaluable for troubleshooting, insurance claims, and resale value. It's also required if you ever need warranty service on a component — manufacturers want to see how it was installed. On every build that leaves our shop, we provide full documentation as part of the handoff process.

How Long Should a Van Conversion Actually Take?

Van conversions take longer than you think. Parts get backordered. Problems reveal themselves during the build. Design decisions need time to settle. Rushing leads to shortcuts, and shortcuts create the exact problems on this list.

In our shop, a basic build takes 6–8 weeks. A standard build runs 8–12 weeks. Premium builds with complex interiors and integrated systems take 12–16 weeks or more. These timelines assume a professional shop working full-time on the build.

If you're doing a DIY build on weekends, realistically double or triple those numbers. And if you're planning a big trip as your deadline — build in buffer. You don't want to be finishing your electrical system the night before you leave.

Related Pages

Related: All How-To Guides • Systems & Guides

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