Medium Density Fiberboard or MDF is not intended for outside use. This product has many wonderful uses (inside) cabinet bodies being one of them. However, you have already heard two excellent reasons why it is not used outside or for mobile projects. It is made by mixing sawdust essentially, with glue. When water hits it the sawdust expands, deforms the glue and it never regains its shape again. And, it's ungodly heavy (you don't have to move cabinets around once they're in place!). Use pine, fir or cypress!