He said he normally uses pressed solid oak for the treads, and an mdf type of material for the stringers (which is then veneered)
Does this seem right?
I thought staircases were made of solid wood...or maybe they are more prone to warping?

Here is a link to one staircase he has done.

http://flickr.com/photos/bakerbotsbakingco/1701848245/
Comments?
I will call his references tomorrow.

THANKS!

I'm not a stair builder, but MDF does seem like an unlikely choice for stringers. It's a fine material for certain applications, but stringers require some tensile strength that I doubt MDF can provide. I did a search on a professional woodworking forum for "MDF stringer" and got no relevant hits.

Having said all of that, the picture looks nice. He could be a fine stair builder and a lousy communicator.

Components to staircase-
The stringers are made of layers of plywood, regular plywood in the core and veneer plywood for the outer visible surfaces.
The risers would be made of either 1/2" veneered particle board or 1/2" veneered plywood depending on availability of species of wood chosen.
the treads will be solid hardwood and so will the trim.