ASCE 7 ASD Load Combinations: Governing Demand and Net Uplift
The governing demand and net uplift across the seven ASCE 7 ASD load combinations.
Example
You enter
- Dead load D (psf) 15
- Roof load Lr/S/R (psf) 30
- Wind load W (psf, + down / - uplift) -25
- Roof load type snow-7-22
You get
- Governing gravity demand 36.00 psf
- Controlling (min) case -6.00 psf
- Net uplift 6.00 psf (resist)
Checked against published worked examples from: STRUCTURE magazine (Showalter and Adams).
Details, formula, and sources
ScopeCombines dead, live, roof (snow/rain), and signed wind into the seven ASCE 7-22 §2.4.1 basic ASD combinations, with 7-22 snow at 0.7S (strength-level) and a 7-16 snow or roof live at 1.0, and returns the two cases the trades design to: the largest gravity demand (which sizes the beam, joist, or footing) and the most negative case (which, when 0.6D + 0.6W goes below zero, is the net uplift the roof-to-wall hold-down must resist). A member is never designed for one load at a time - the governing combination is, which is why the design starts here, not at the largest single load. A load-combination aid, not a member design.
Formula or tablecombos = [D; D+L; D+kS; D+0.75L+0.75kS; D+0.6W; D+0.75L+0.75(0.6W)+0.75kS; 0.6D+0.6W], k = 0.7 for an ASCE 7-22 snow load, 1.0 for a 7-16 snow or roof live / rain; governing_gravity = max(combos); controlling_case = min(combos); net_uplift = controlling_case < 0 ? -controlling_case : 0.
Source and editionASCE 7-22 §2.4.1 basic ASD load combinations (2024 IBC), by name, with the 7-16 snow factor of 1.0 available for a service-level snow.
Free accessThe basic ASD load combinations are stated in ASCE 7 §2.4.1; the arithmetic is public.
What governsEstimate. AHJ and licensed professional govern.
API field namesdead_psf, snow_psf, wind_psf, roof_load, governing_gravity_psf, controlling_case_psf, net_uplift_psf
- Snow factor 0.7S for an ASCE 7-22 (strength-level) snow; 1.0 for a 7-16 (service-level) snow or for Lr or RASCE 7-22 §2.4.1; ICC, Demystifying Loads (2024 IBC / ASCE 7-22)
- Governing gravity the largest of the seven combinations is the downward demand that sizes the memberASCE 7 §2.4.1
- Net uplift when 0.6D + 0.6W (or another case) goes below zero, the magnitude is the uplift the connection must resistASCE 7 §2.4.1
- Signed wind wind is entered signed: positive downward (pressure), negative upward (uplift)first principles