I just had a new birch floor intalled over and old 1850's pine plank floor. The planks were used as the subfloor as opposed to adding a layer of plywood. The floor ahs severely buckled in one week. The installer left no room for expansion..says he always does it that way. The floor was laid in the opposite directioon of the floor joissts. Now the installer has pulled up some of the floor and says that the joists are uneven and that I should expect "some" roll in an old floor. I have since heard that when laying new planks over other planks that you should actually go the opposite direction acrross the existing plnks so that it ends up going the samne direction as thee joists. My floor guy disputes this. Is this true? Will the floor be strong enough? Help soon, we're trying to resove this and I hate to settle for a "rolling floor" if I don't have to.