30 Foot Span?


I have designed my own floor plan. The living, dining, and kitchen are all placed in one 25' x 30' room.

The joists will span across the 30' direction with an additional 5 feet over a porch in the front and 8feet over the porch in the back. In your experience, is this a safe distance to span?

To avoid issues of sagging and or failure and so forth, how would this be done?

Thank you,


Do you remember that TV show from the 1960's called "The Outer Limits"? I think you're headed past there with your floor plan.

The largest, readily available solid lumber floor joists are 2x12s. They will span up to 20 feet depending on the species and the spacing. Plywood web joists, or TJI Joists, will comfortably span between 20 and 25 feet depending on the manufacturer, depth and spacing.

Weyerhaeuser, and perhaps others, do manufacture larger (up to 20" deep) TJI Joists which will span over 35 ft, but I've never used them, and I'm not sure they would be cost effective if you have other options. In your case, I would consider changing the direction of your framing to the 25' dimension and using moderately sized TJI Joists.
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