How do you span 40 foot floor joists with no supporting beams in a residential building?

Suggestion 1. Design a built-up truss.

Use the Pratt Truss as template. It is one of the simplest to design and make. It has horizontal top and bottom chords which you can use to support a suspended slab.

Suggestion 2. Wide-flange beam.

Wide Flange Beams can be designed with large spans and are easy to install.

Suggestion 3. Design a flat slab RCC floor.

A flat Slab combines a Beam and Slab

Suggestion 4. Use Pre-stressed Beam

Beams with tensioning tendons allow for long spans without increasing depth. This is usally employed in multi-storey RC Buildings with clear spans 10m or larger.

Final Verdict: If you value speed and ease of installation, I would strongly suggest Suggestion 2. Suggestion 1 has the best strength to weight ratio, followed by Suggestion 4. I would not normally recommend Suggestion 3 unless the architect wants a clean and flat slab soffit.


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