Have a look at t&g (toungue and groove) ipe decking also straight grain fir is the classic.

You don't say what's below dirt or indoor space or if it's an insulated space or outdoor... ply or just framing.. so my wild assumption is that it's an enclosed space with uninsulated floor over exterior soils.

Hope I'm right. ;)

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Yes, it's going over the previous bare outdoors--i.e., just being added where nothing existed before.

So maybe a slightly raised deck with T&G flooring would be an alternative? Would you insulate with something?

Not if it's an unheated space.

Alter Eagle Construction & Design

http://www.altereagle.com/ | Construction & Design | http://decks-ca.com/ | Decks, California outdoor living | http://kingofcrown.com/ | Molding and finishing | http://installcrown.com/ | Crown tutorial