All exposed edges will be lipped with solid timber . A few reasons for using veneered mdf , the first is cost , without having my sums in front of me the job is around £2500-£3000 . If done in solid walnut i think with jointing the timber and extra cost of the timber the job would be around 3-4 times as much . Next is the idea of joining solid boards together making a very nice job and putting it in a room that will be full of steam a few times a day . Maybe they do a moisture resistant mdf veneer ? or i could use veneered ply .