MDF sorta rings a bell, thanx Steve.
2x6 shouldn't sag too much I hope Kent... I sat on the middle of each long span & the bubble moved a little bit. I have the outside edges tipped up to the high side of the bubble mark so the screws & tools, if they wanna roll will go towards the wall rather than off onto the floor... till I get a bunch of projects spread across the area, then maybe it will hold level.
The middle of the floor will be left open for now. I have had thoughts of making a rolling bolt bin - tool carrier to drag from one project to next, regular use tools & parts at easy reach.
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Thanx Reg. How big is your shop & when did you build it?