if you can do a 9x12 rug, so that the sectional front legs are on it, that would give you great definition to your open space. area rug tips

The area rug should be anchored by the front legs of the sectional as in the pictures below, but it doesn't need to go completely underneath the entire sofa. Depending on whether or not you are planning to add chairs, you may want to get a larger size so that all your furniture including the chairs are grounded by the rug. Hope these pictures help.

Adrienne DeRosa Photography © 2013 Houzz · More Info

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I love wood floors and since yours are so beautiful, don't cover them completely. I believe with the style of your sectional a nice pattern (that repeats occasionally in other places around the room....art, curtains, pillows, etc) or modern shag would look wonderful.