Is oak wood safe for hamsters?

[turbowurbo]

I want to build a second story loft for my hamster. The main platform is birch but the legs and the fence are going to be made of oak wooden dowels. I am going to cover the whole thing in butcher block finish to make it urine proof. So this is not bedding or a chew toy, but there is a chance he could chew on it a bit. Will the oak wood be toxic or is it safe to use?