I began version one of my Vardo Caravan eleven years ago this month. As I published updates and details along the way people have for a detailed “how to” for building a vardo. Since everyone’s needs, skills, and resources are different, I will leave the task to others. My suggestions are this. Decide on your basic design wants. Traditional or modern construction? Consider size and weight (I went for the minimum of both). Consider materials. This will determine construction technique. As for traditional or modern? Go look at some used RVs for sale and see how flimsy they are built; not to mention probable issues from toxins in the plywood, pressboard, adhesives, plastic veneers, etc.
Drink in as many details as possible about other wagons. Are they for show or can they take the hammering of bad roads? How do you think they will hold together in a wreck? What kind of long-term maintenance are you prepared to perform? This is why modern RVs are covered in sheet metal or plastic. If you convince yourself that you want to use materials others don’t, then ask yourself why. Are you building an RV that looks “old fashioned” or are you deciding to build with traditional techniques? (Neither is bad, but it may not be practical to mix and match).
Above is the written plan I used to create the Vardo. This is obviously not exactly how it turned out as changes were made based upon availability of materials and constant reconsidering of different options. The essentials didn’t change. This is how the arc of the roof was calculated and overall dimensions worked out. I chose to use traditional techniques and plywood only in the ceiling (for ease of building and stiffening the structure). Although glue is used in some areas, the structure depends upon screws and bolts in all critical areas. I decided I was willing to maintain my wagon so the exterior finish is simple oil paint over wood.
The second sheet of the plan was mostly used as a way to gauge sizes, raw materials, and habitable space. I didn’t really build from the sheet.
This is just one of many sketches used to figure out space and arrangements. I looked at Irish Open Lots, Vardos, Bow Tops, and Sheepherder wagons. With so much experience out there, the best arrangements have been worked out many times over. Here’s the link to the rest of the photos from the build: https://paleotool.wordpress.com/plans-projects-and-patterns/the-vardo/
Study and read as much as you can about what you want to build. Make many sketches and plans. Cut out little scale paper dolls to measure out spaces if it helps.
Make a model.
Take a deep breath.