Plywood is a common material used in building a doghouse because it is readily available and in most cases economical.
There is a variety of thickness with plywood as well as different grades whether it is interior or exterior quality.
The exterior plywood is usually more expensive when compared to the same thickness in interior grade.
The ideal plywood would be Marine grade because it is designed to stand up to the elements.
Plywood is an excellent choice for kit type homes because it is easy to construct panels that can be easily shipped and assembled.
Like any other wood if plywood is properly treated and painted it has the potential to last a very long time.