Siding is the outer layer of the tiny house, and a large variety of materials are available for your choosing. Popular materials available are: Vinyl, Fiber Cement, and Wood.
Vinyl is famous for being maintenance free! The vinyl siding is available in many different colors, and you install the color that you want to use. It never needs painting or coating, as the vinyl is its own color. It is also very light weight, which is a wonderful bonus for a tiny house. The big weakness with vinyl siding deals with impact damage. Since it is made of weak plastics, it dents easily. It also doesn't hold up very well to strong winds.
On a tiny house being towed down the highway will expose the tiny house to hurricane force winds (64 knots or 73.6 mph) and road debris impacts on the siding. If you are never going to move your tiny house, vinyl may be a very simple option for your choice in siding material.
Fiber cement boards are much heavier than vinyl, but they are also much stronger. They hold up to impact and high winds much better, making them a wonderful choice for tiny house siding. Fiber cement does require painting, and this paint needs to be maintained over the years of the life of the tiny house. While this is added maintenance over vinyl, it does give you the ability to change the color of the tiny house over the years.
Lastly, wood siding is a wonderful material with the same benefits of fiber cement, but it is much more expensive. Wood siding can be finished with oils or varnish, letting you keep the look of wood that you can't have with fiber cement. Different woods can be troublesome to maintain painted. Some oily woods will be harder to make paint stick, and these woods will be condemned to paint peeling off the house.
If you decide to use wood siding, be sure that you select the correct species of wood for the finish that you want to achieve on your house.