In 1996, I built a sturdy foundation and well-insulated walls and roof for a 600-square-foot house at a cost of $5000, and I ended up with a complete house for $6200. My unique building method offered a number of advantages, among them low cost and easy construction, but it also came with some disadvantages. I'll explain both as we continue. I'll give you an overview of the process, photographs of each of the major building stages, and lots of unique details, but a complete building plan is far beyond the scope of this site and my very limited expertise. Before this project, the biggest thing I had ever built was a storage shed. If you can handle this project in general, you'll be able to fill in the exact specifications you need for your own low-cost, energy-efficient house.
The structure I built is essentially a pole building with a steel roof, 2" Celotex insulation, and hardboard sheathing/siding. To save a huge amount of money, materials, and labor, I used an old 12'x50' mobile home as the interior. The mobile home cost $800, plus $400 in repairs. Materials for the new structure cost very close to $5000, hence the $6200 total ($5000 + $800 + $400). The structure is completely independent of the mobile home, and the house shell would have been built the same way--with the addition of floors, windows, and doors--if the interior were to be built from scratch. The cost of building the entire house from scratch would depend greatly on your ability to do plumbing and wiring, make counters and cabinets, and obtain inexpensive materials, but given that you'll have walls, a rock-solid foundation and roof, and excellent insulation for around $6000 (allowing for inflation since 1996), you'll be off to a great start on keeping your building cost to a fraction of what most people spend on a house of comparable size.
If you could live in an inexpensive mobile home, why bother building at all?
I liked the idea of making use of an old mobile home instead of seeing its tons of materials end up eventually torn down and added to an overburdened landfill somewhere. Reusing the old mobile home also greatly reduced my need for new materials, all of which would have been produced at a significant environmental cost. You can find old, single-wide mobile homes sitting at the backs of dealers' lots all over the country, and many dealers (and private owners) are so eager to get rid of them, they'll sell them for next to nothing.
If a single-wide mobile home is too narrow for your tastes or needs, an interesting solution I've seen done is to bolt two of them together, side by side, and cut doors through the adjoining walls where needed. With proper footings underneath each unit and a new roof overhead, you'll have a solid, leak-proof structure, and two inexpensive, 12'x50' units will give you by far the cheapest 1200-square-foot house possible. If you use two mobiles with house-style (not cranking) windows and fully enclose them in a new structure with a peak roof, you can make your home look almost exactly like a conventional house.
Of course, when we're talking about older mobile homes, "cheap" cuts both ways. By building a new structure around the mobile, you'll eliminate its main practical disadvantages such as poor insulation and leaks, but you'll still have a cheap interior. If that's unacceptable, you can build a pole house from scratch, with the only major difference in framing being the need for a floor. You'll have to install interior walls, wiring, plumbing, counters, cabinets, fixtures, etc., but shopping carefully, using recycled materials, and doing the work yourself can make a huge difference in keeping costs low.
Whether you plan to build a pole house from scratch, build around a single mobile home, or build around two mobile homes, you'll need a building permit. Pole buildings are commonly used for garages and barns, and given their structural strength, they should be easily accepted for houses too. Many areas don't allow mobile homes, but the fact that you'll be completely enclosing the mobile might help, and you might be able to meet a square footage minimum by using two.Next: Features