Snow load guides
A plain-English walkthrough of the ASCE 7-22 roof snow load calculation: ground snow load, the flat-roof equation, the slope factor and the minimum load.
What ground snow load (Pg) means, why it varies so much by location and elevation, and exactly where to look up the value for your site.
Planning ranges for ground snow load across all 50 states, with the mountainous case-study states flagged. Always confirm the exact value with your AHJ.
ASCE 7-22 reworked how ground snow load is determined and added reliability-targeted values. Here is what designers need to know.
Why roof snow load is usually less than ground snow load, and the exposure, thermal and importance factors that connect them.
How snow drifts form at roof steps, parapets and walls, why they can be the governing load case, and how to size the drift surcharge.
Snow weight depends on density, not just depth. Here is how to estimate roof snow weight and why a foot of wet snow can be 5× a foot of powder.
Why metal roofs count as 'slippery surfaces' in ASCE 7, how that lowers the slope factor, and the sliding-snow hazard to plan for.
How rooftop solar interacts with snow load: added dead load, changed sliding behaviour, and what to check before installing.
How to tell what your roof was designed to carry, warning signs of overload, and when to remove snow.
Plain-English definitions of Ce, Ct and Is, the three ASCE 7 factors that turn ground snow load into roof snow load.
Flat roofs carry the full snow load with no shedding, plus rain-on-snow and ponding risk. What to watch for and how to design.
Most code-built roofs handle 20-40 psf. Here's how to estimate what's on your roof, how to find your design limit, and when to remove snow.
When roof snow load approaches the design limit, raking is safer than waiting. Here's how to judge the risk and remove snow without getting on the roof.
Sticking doors, sagging ceilings and cracking drywall all signal roof stress. Here's how to read the warning signs before snow overload becomes a collapse.
Your zip code determines your ground snow load. Here's how to look it up, what it means, and how to turn it into a roof design load using ASCE 7.
Ice dams form when heat escapes through the roof and melts snow that refreezes at the cold eave. Here's how they form, what they cost, and how to prevent them.
Unbalanced snow load governs gable roofs when wind piles snow on one side. ASCE 7 §7.6 requires a check; here's how to calculate the design case.
Three worked examples of the ASCE 7-22 flat-roof snow load equation -- standard house, unheated garage and an exposed warehouse -- with all factors shown.
When a slippery roof sheds snow, the mass lands on the lower roof or walkway below. ASCE 7 §7.9 sizing for sliding snow surcharge, explained step by step.
After a storm you want to know if the snow sitting on your roof is within design limits. Here's how to estimate the load from depth and snow density.
Sheds and detached garages often have minimal roof structure. Here's the ASCE 7 process for finding the design snow load for outbuildings and light framing.
Decks, balconies and open porches must carry snow just like any roof structure. Here's how to find and apply the design snow load for outdoor platforms.
High-snow regions require roof designs that account for drift, unbalanced and sliding loads in addition to the uniform load. Here's a design checklist.