What Deflection Limits Apply to Type B Deck in Florida?
The Florida Building Code's deflection table sets roof limits by what the roof supports, and the engineer of record picks the one that applies. Our Type B catalog gives the uniform load that causes L/240 deflection at each span, with factors to convert to other limits: 0.667 for L/360, 1.5 for L/180 and 2.0 for L/120. We supply the gauge your engineer selects.
How to use the deflection table
Find the gauge, span condition and span, read the L/240 load, then multiply by the factor for your limit. Example from the catalog: 20 gauge triple span at 6'-0" carries 108 psf at L/240, about 72 psf at L/360 (108 x 0.667). Compare that with the service live or snow-free roof load, not the factored load.
Why deflection often governs
On single spans, deflection tends to control before strength. 22 gauge single span at 6'-0" allows 91 psf for strength but only 45 psf at L/240. Continuous spans are much stiffer.
- Ponding on low-slope roofs is sensitive to deck and framing stiffness.
- Ceilings or finishes attached below may need a tighter limit.
- The engineer chooses the limit; the catalog only provides the loads.
Next step
Send the spans and limit from your structural notes and we will quote the gauge that meets them.
Uniform service load causing L/240 deflection at 6'-0" span, psf (catalog)
| Gauge | Single | Double | Triple |
|---|---|---|---|
| 22 | 45 | 109 | 85 |
| 20 | 57 | 138 | 108 |
| 18 | 81 | 195 | 153 |
| 16 | 108 | 260 | 204 |
Related Questions
Does wind uplift deflection matter for Type B?
Strength under uplift is the usual concern, and the catalog publishes separate ASD upward load tables for that. Deflection limits usually focus on gravity loads because they affect ponding and finishes. The engineer of record decides whether any uplift deflection check applies to your roof.
Why is the double span stiffer than the triple span in the table?
For deflection, a two-span sheet restrains both spans at the middle support, so its maximum sag is smaller than in the end spans of a three-span run, which is why the L/240 loads for double span are higher. Strength tables show the opposite pattern. Use the value for your actual span condition.