I used 'SketchUp' Pro to design my proposed trailer home before the software's trial period ran out. I can begin welding the stell frame for the 20ft trailer base once I have completed helping a friend construct a garage over the next 2 to 4 weeks.
I am not sure what sort of construction method that I will use for the walls. I really want a relatively light weight trailer so that I can hitch it to a light truck like a Ford F100 or one of the modern pickup /utes. I may use refridgerator sandwhich boards for the outer walls but I still need a means of supporting the loft. I really dont want to use wood due to weight. I may be able to weld a 40mm square tubular steel frame. This is twice as heavy as Aluminium but half the cost, stronger and easier to weld. I would like some sort of thin wood composite inner wall lining with an insulating metal foil then a 10mm air gap and then a 30mm sandwhich panel (second hand).
Originally I had wanted a rustic looking wood exterior, but realistically I didn't want to use a large truck to haul it. Although the wheels will be rated to 4.5 tons, the trailer needs to weigh less than 3.5 tons fully loaded to enable a lighter pick up or ute to move it.
I hope to fit out the interior with cabinetry that I get for free from Gumtree.com.au. As yet I do not have a budget for the entire project. The big expence will be the wheels and solar panel, battery, inverter system. Initally I will just get one solar panel and a cheap battery to run some LED lights. Later I will purchase more panels and proper deep cycle batteries and inverter etc. I will need to install a parallel 230V AC system and will need an electrician to sign off on it. I will hide the wiring behind the cupboards as opposed to putting it between the walls.
The main thing is to get the trailer base welding completed and then the lower floor, walls, loft floor and roof up quickly. Then I can relax and fit it out at a more leasurely pace. If I can use a simple prefabricated wall panel construction method then that should make the construction quick and simple.