Expert: Bruce E. Johnson - 6/14/2010

Question
I have a house in Colorado Springs built @ 1995 with a basement wherein part of it has a dirt floor.  The dimensions of this area are about 16'x 20'.  The basement walls are poured concrete.  I have no water issues or cracks.  I am wanting to excavate the dirt down to where I can add joists and flooring to finish the room.  The dirt is very sandy in texture and I would rather do joists than pour a concrete floor as I would not trust the sand to support concrete.  I have two questions:  1.) Should I use 2x8 (or other size) lumber for the joists?  Or should I use those engineered joists made of OSB between two 2x2s?  2.) What is the best way to anchor the joist to the inside of the concrete footers?

Thanks for your help -- Curtis

Answer
Hi Curtis, I would suggest that you pour concrete.  Sand is one of the best bases for concrete if it is compacted.  However, if you are set on doing a wood floor, 2x8s would work fine if you had an intermediate footing to support them.  A 2x8 should only span 8-10 feet.  As far as attaching to the footings, an epoxy bolt or a wedge anchor 1/2" in diameter and long enough to give you 3 inches of embedment into the concrete should suffice. These products are easily attainable at Home Depot or other hardware supply stores.  Be sure to use pressure treated wood everywhere and put down a vapor barrier of 6 mil visqueen to block moisture coming up from the ground.I hope this information helps please feel free to write again regarding this or other matters, sincerely bruce e johnson..bejohnsonconsulting.com