This section provides information that should help you to design and build your own RV or camper van conversion.  There are pages on selecting a good base vehicle, choosing the best interior layout for you, and design/build sections for walls, floors, windows, insulation, electrical and solar, plumbing and tanks, … Even how to build your own composting RV toilet!

If you don’t see what you want leave a comment and maybe we can find something.

Index to Design and Build Pages



September 3, 2015, July 1, 2016

Comments, Suggestions, Questions, Ideas?

What else would  you like to see more design and build info on?


12 Responses

  1. Does anyone have ideas or guidance about venting gray and Black water tanks? Are they usually vented through the roof? Are there particularly good fittings or caps for them?

    1. Hi Gary,
      I tried not venting the grey water tanks and that did not work — lots of gurgling and slow draining of water from the sink. Added a vent at top of tank that just goes to a place a few inches from the tank (not up through the roof). This has worked fine without any leakage or odor from the vent.

      On RVs, it is common practice to run the vent up to the roof, and this may be the best way, but does not seem necessary (at least for grey water). Amazon sells the vent top fittings for roof vents.

      We use a composting toilet, so no black water tank.


  2. Hi. Before going into details of how to carry out each task it would be helpful to provide an overview of the order in which they should be done. Thanks.

    1. Hi Ruby,
      I’d be glad to add the overviews.
      Could you give me an example of what you think would work for one of the pages?


  3. I am also planning a Promaster build for four — two adults and two kids 5 and 9. Most European models based on the Promaster design use a “bench” seat behind the driver to sit two kids. If you know kids this is not a good idea for harmony. Due to safety concerns, sitting in the back in a “dinette” area is not attractive either. I have concluded the only option is two bucket seats attached to the floor behind the front driver and passenger seats. There are many online sellers offer attractive seats with seatbelts attached for about $500 each. Then you need another $100+ for the seat brackets. It’s expensive, but having safe “real” car seats, with space around them for the growing kids not to annoy each other is important. The tough call is sleeping for four. Pop tops are only available on short wheel base vans and that won’t do. So it is bunk beds — rack and stack um — to fit four in.

    1. Hi Scott,
      I’ve never tried to work out an interior like that — it seems like it will be a challenge to get it all in if the new seats are only used for seating. I wonder if there is some safe way to get that area to serve two functions?

      I think it would be worth asking for ideas on the ProMaster, Sprinter and Transit forums. The ProMaster forum has a thread dedicated to interiors.


    2. Hi Scott,
      We recently completed a Promaster build for 4. We have a 6 and 3 year old. The challenge we ran into was how to get the seating installed safely. Many of the conversion companies are putting in steel plates to help reinforce the floor, but we weren’t comfortable with the way a lot of the companies were doing it. We ended up having a floor and seating installed by FR Conversions. Their floor was affordable compared to other conversion companies, and we feel better about knowing our kids seating has passed crash testing. My husband did rest of the conversion himself. We’ve had 6 trips since completing the van in April- we all love it, and are super happy. We actually ended up adding in 4 seats so we can take grandparents with us. We have sleeping for 4, seating for 6, a galley with water, fridge and sink, solar etc. And it feels like plenty of space.

    1. Hi Noah,
      Mostly I used pencil and paper, but did do a little with the tool that the Sportsmobile site has. A lot of people use Sketchup, and I think there are some Sketchup models in their “warehouse”.

      There is more on modeling tools on this page:

      In the end, we built actual models in the ProMaster for the two layouts we liked the most. We just used scrap wood and cardboard — actual 3D models in the PM really tell you a lot that paper and computer models don’t.


  4. Hi Susan,
    We never looked into adding seats as we only had the need for the two up front.

    It seems like I have seen commercial seats available, but can’t remember the company.

    Probably a good place to start would be the forums for the 3 main vans — you could search the existing posts and also post your question there. This page has links for the PM, Transit, and Sprinter forums:

    Also, a lot of the European van conversion RV’s are based on the Ducato, which the PM is derived from — it might be worth looking at what some of those conversions do for extra seating. There are dozens and dozens of European conversion deisigns out there.

    One last thing would be to see what Sportsmobile offers: http://sportsmobile.com/ I’m sure they have some options for extra seating.


  5. I’m interested in information on installing seats. I want to do a promaster conversion that can sleep and travel four. I have two little kids, and know there are limited options for where the seats can be safely installed.

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