Snow Load and Roof Framing in Massachusetts
Massachusetts winters are brutal on roofs. The 2015 winter (108.6" in Boston) collapsed gas station canopies, gym roofs, and barn structures across the state. Most of those failures were not built to current code.
Here is what proper roof framing for MA snow loads looks like.
What Is the Snow Load Where You Live?
The MA State Building Code (780 CMR) references ASCE 7 for snow loads. Ground snow load (P_g) varies by county:
- MetroWest / Worcester County: 50 psf
These are GROUND loads. The actual roof load is calculated with exposure factor, thermal factor, importance factor, and slope reduction — typically 0.7 × ground load for an ordinary heated home.
Why It Matters for Framing
A 50 psf ground load means your roof structure is designed to hold 35 pounds per square foot of snow. On a 2,000 sq ft footprint, that is 70,000 pounds sitting on the rafters and walls.
Get the rafter sizing wrong, miss the collar ties, skimp on rafter ties — and the entire roof can sag, bow, or in extreme cases collapse.
How RS Development Group Frames for MA Snow
When we frame a new roof or addition in Massachusetts:
1. Use the actual local snow load. Marlborough is 50 psf. Cambridge is 40 psf. Williamstown is 60+ psf. We calculate for YOUR location, not a generic default.
2. Engineered rafters or trusses. For spans over 16 feet, we use LVL/PSL rafters or pre-engineered trusses with stamped design loads. No guessing.
3. Proper collar ties. Code requires collar ties at top third of attic for gabled roofs. We install them on 4-foot centers minimum.
4. Rafter ties at heel. Every rafter pair gets a tension tie at the wall plate. Without these, the rafters spread under snow load and push the walls outward.
5. Hurricane ties on every rafter. Simpson H1 or H2.5 minimum. These resist uplift in wind AND prevent rafter movement under snow load.
6. Beefier wall framing under load points. Where roof beams or trusses bear, we double or triple the wall studs and provide a continuous load path to the foundation.
Warning Signs Your Roof Is Under-Framed
❌ Visible sag in the ridge line ❌ Cracks running up the walls in the attic ❌ Doors and windows on the top floor that stick after a snowstorm ❌ Audible creaking during heavy snow ❌ Sagging gutters or eaves after winter ❌ Water staining at the top of walls (ice damming caused by overstress + ventilation issues)
What to Do
If your home is more than 25 years old and you have not had a structural inspection, get one. MA snow loads changed in the code in 2008 — older homes were designed to lighter standards.
If you are adding a second story or dormer, the existing structure MAY not support the new load. We always do a load path analysis BEFORE framing.
If your roof shows any of the warning signs above, do not wait until winter. Get it inspected now.
Free Inspection — Call Today
📞 (774) 512-3176 — Same-week visit across MetroWest MA 📧 info@rs-developmentgroup.com
In the trade since 2008. Licensed Construction Supervisor. Latino-owned.
