Deck Snow Load in Massachusetts by Town

A residential deck in Massachusetts has to be designed for the snow load of the town it sits in, not a generic 40 psf number. In Boston that load is 40 pounds per square foot, in Worcester and Pittsfield it is 50, and in Berkshire hilltowns like Savoy, Florida, Windsor, Becket, and Worthington it is 60. The prescriptive deck guide most contractors built off for two decades (DCA-6, published by the American Wood Council) was sized for a 40 psf load, which means a deck built off DCA-6 alone in a 60 psf town was never sized for the snow its zip code can actually drop on it. The 10th edition of 780 CMR, effective October 11, 2024, finally added joist and beam tables in R507.6 for 50, 60, and 70 psf ground snow loads. Decks built before that date in high-snow towns are the population to worry about.

This guide gives you the ground snow load (Pg) for your town, the math on what your deck was probably designed for, and a real decision tree on shoveling after the kind of storms eastern Massachusetts saw in January and February 2026.

How much snow can a Massachusetts deck hold?

A code-compliant Massachusetts deck has to handle either the 40 psf residential live load or the ground snow load Pg listed in 780 CMR Table R301.2 for its town, whichever is greater. Live load is the people-and-furniture load (a 200-pound person at a hot tub party, a grill, planters). Snow load is the weight of accumulated snow. The deck does not get to add them, but it has to survive whichever one governs.

The 40 psf number gets used a lot because the American Wood Council's DCA-6 Prescriptive Residential Wood Deck Construction Guide, the document almost every deck builder in the country has on the truck, is sized for a 40 psf uniformly distributed live load with a 10 psf dead load. Per the AWC's own FAQ, that criterion "can be conservatively applied to a deck with a uniformly distributed snow load of 40 psf and a 10 psf dead load" as long as the deck is not prone to sliding or drifting snow. So DCA-6 covers any town whose Pg is 40 or less.

In Massachusetts, that is roughly the eastern half of the state and the Cape and Islands. It is not the Berkshires, the Worcester plateau, or the hilltowns of Hampshire and Franklin counties, where Pg runs 50 to 60. For those towns, DCA-6 alone does not get you to code.

Ground snow loads by Massachusetts town

These values are from Table R301.2(4) of 780 CMR. The 10th edition retains the jurisdiction-by-jurisdiction format. If your town is not in this table, your local building department has the official number; call and ask, do not assume the neighboring town's value carries over.

Region	Town	Ground snow load Pg (psf)
Cape and Islands	Provincetown	25
Cape and Islands	Nantucket	25
Cape and Islands	Edgartown (Martha's Vineyard)	25
Cape and Islands	Barnstable	30
South Shore / Southeast	Plymouth	30
South Shore / Southeast	Fall River	30
South Shore / Southeast	New Bedford	30
South Shore / Southeast	Brockton	35
Greater Boston	Boston	40
Greater Boston	Cambridge	40
Greater Boston	Newton	40
Greater Boston	Quincy	40
Greater Boston	Lynn	40
Pioneer Valley	Springfield	35
Pioneer Valley	Northampton	40
Pioneer Valley	Greenfield	50
Merrimack Valley	Lowell	50
Merrimack Valley	Lawrence	50
Central MA	Worcester	50
Berkshires	Williamstown	50
Berkshires	Pittsfield	50
Berkshires	Adams	60
Berkshires	North Adams	60
Berkshire / hilltowns	Savoy, Florida, Windsor, Becket, Worthington, Peru, Hawley, Heath, Monroe	60

A few patterns are worth naming. The coast is the lowest-load zone in the state because the ocean moderates the cold and rain is more common than snow. The Greater Boston Pg is 40 across the urban ring even though storms there can dump three feet in a single nor'easter. The 60 psf belt runs through the high Berkshires and into the hilltowns of western Hampshire and Franklin counties at elevations roughly above 1,500 feet. Worcester at 50 is the central-MA standard.

What the 10th edition changed in October 2024

Before October 11, 2024, Massachusetts decks were built under the 9th edition of 780 CMR, which adopted the 2015 IRC. The deck section, R507, contained joist and beam span tables sized for 40 psf live load. If your deck sat in a 60 psf town, the prescriptive table did not technically cover you, and your designer was supposed to drop into engineered design (or use AWC's expanded tables, which were not yet in the code).

The 10th edition adopts the 2021 IRC. R507.6 now contains four sets of joist span tables: 40 psf live load, then 50, 60, and 70 psf ground snow loads. R507.5 does the same for beams. R507.9 added ledger connection details for 50 and 70 psf snow loads. For the first time, a prescriptive deck built straight off the code in a Pittsfield, North Adams, or Becket backyard is actually sized for the snow load on its property.

The practical effect on permits is also new. A deck permit submitted today in a Berkshire or hilltown building department will be reviewed against the 60 psf table, not the 40 psf table. A homeowner repairing or expanding an older deck will trigger that same review on the work area. A like-for-like decking-board replacement is a different story (see our guide on deck maintenance), but ledger, beam, or joist work in a 60 psf town now lives by the bigger numbers.

Was my deck designed for the right snow load?

The question matters most in the 50 to 60 psf belt. In Boston, Plymouth, or Barnstable, a deck built to DCA-6 was already sized for the code Pg. In Pittsfield, Worcester, or Adams, it may not have been.

The decision tree:

Town's Pg	Deck built before 10/11/2024	Deck built after 10/11/2024
25 to 40 psf	Sized correctly if it followed DCA-6 or R507	Sized correctly if it followed R507
50 psf	DCA-6 alone undersized the joists and beams; check whether the builder engineered up	R507.6 covers it directly
60 psf	Same problem, worse; the gap to design Pg is 50 percent	R507.6 covers it directly

The honest read: a deck built in 2008 in Becket off the same span tables a builder was using in Quincy is the textbook example of a deck that may carry the 40 psf load it was sized for and still be over its town's design snow load. That does not mean it will fall down. Decks rarely collapse on the joists; they collapse at the ledger, where snow load adds to a connection that may also be rotting from freeze-thaw water intrusion. Our guide on deck ledger flashing and collapse in Massachusetts covers that failure mode in detail. But the math is the math.

Three honest steps to figure out where you stand:

1. Find your town's Pg in the table above. If it is 40 or below, the rest of this section does not apply to you.
2. Pull the deck permit from your town building department. If the year is 2024 or later and the deck is in a 50 to 60 psf town, ask which table was used. If the year is earlier, the original design almost certainly used the 40 psf table.
3. If the design Pg is below your town's Pg, get a structural look at the joist size, joist spacing, beam, and ledger. A lot of older decks in high-snow towns were quietly over-built (six 2x10 joists at 12 inches on center when DCA-6 only required 2x8 at 16 inches), in which case you may already be fine. A lot were not. Only an actual measurement tells you.

Should I shovel my deck after a big storm?

Shovel a deck only when the accumulated snow is heavy enough to approach the design load, the deck is already showing distress, or you have a covered porch where drifting can pile snow against a wall. Shoveling for the sake of shoveling beats up the finish and is not safer than leaving fresh dry snow alone.

A rough working number: wet, packed snow can run 15 to 20 pounds per cubic foot, fresh dry snow 5 to 7. Three feet of dry snow at 6 pounds is about 18 psf, well below any Massachusetts Pg. Three feet of wet snow at 18 pounds is 54 psf, which is over the design Pg in every town in the state east of Worcester and at the edge in the hilltown belt. This is a rule of thumb, not a code calculation, but it explains why the February 2026 storm in the south shore (which dropped roughly three feet of wet snow in some towns) was the one to worry about, and the dry January powder a month earlier mostly was not. Our guide on deck maintenance through the Massachusetts climate covers shoveling technique in more depth.

When you do shovel:

• Use a plastic shovel only. Metal blades gouge composite caps and tear up pressure-treated grain. Repeat damage on the same boards is how you turn a maintenance task into a replacement.
• Leave a quarter to half inch of snow on the surface as a buffer. You are not trying to expose bare decking.
• Shovel parallel to the boards, not across them. Edges catch and chip.
• Do not use rock salt or any chloride ice melt on wood or composite decks. Chloride attacks galvanized fasteners and stains both surfaces. Calcium-magnesium acetate is safer, but use it sparingly.
• Clear drift accumulation against the house wall first. That is where ledger overload happens.

A covered porch (under a roof) gets a different rule. The shed area on the porch deck itself takes less direct accumulation, but the porch roof above it can shed snow into a drift on the deck, and that drift is concentrated load. Watch for it after any storm with wind.

What if I am over my deck's design load?

If a structural assessment shows the deck is under-sized for its town's Pg, the fix is usually not full replacement. Sistering joists (bolting a second 2x material to each existing joist), adding a mid-span beam on a new post line and footing, or upgrading the ledger fastening to the 2021 IRC connection details will often bring a deck up to a higher load class. Engineered solutions cost less than rebuild. A licensed contractor pulling a permit on the work means an inspector signs off that the math actually works.

Full rebuild becomes the better option when (1) the framing is already partly rotted, (2) the footings are above frost depth (a separate code problem covered in our guide on deck footings and the 48-inch frost depth rule), or (3) the deck is small enough that engineered reinforcement costs almost as much as a new build. A pre-rebuild structural look from a contractor doing deck safety inspections in Massachusetts is the cheapest way to find out which category you are in. Get two opinions before you choose.

If you are planning a new deck right now, the cleanest answer is to ask the contractor in writing which snow load table they are designing to. In a 50 or 60 psf town, the answer should be the corresponding R507.6 table from the 2021 IRC, not DCA-6. That one question separates a builder who has updated to the 10th edition from one who has not.

FAQ

How much snow can my deck hold? Whatever your town's Pg is in 780 CMR Table R301.2, minus a safety factor the engineer or code already built in. In Boston that is 40 psf. In Worcester, Lowell, Lawrence, and Pittsfield it is 50. In Adams, North Adams, and most of the hilltown belt above 1,500 feet, it is 60. Cape and Islands towns are 25 to 30.

Will my composite deck collapse if it has more snow than a wood deck? The decking material does not determine the structural capacity, the framing underneath does. Composite boards over a sound 2x10 joist frame designed to the right Pg are not weaker under snow than wood boards over the same frame. The risk on a composite deck is gouging the caps with a metal shovel during cleanup.

Do I need to shovel a screened porch or three-season room? Usually no. The roof above takes most of the snow. The risk is drift against the house wall on the porch floor, and snow sliding off the porch roof onto a downhill deck section. If either is happening, clear the drift, not the whole floor.

Does the 2026 blizzard exceed my deck's design snow load? Only if the snow accumulated and stayed wet on the deck. Three feet of dry powder is well under the design load anywhere in MA. Three feet of wet packed snow is at or over the 50 psf line in central and western towns and at the edge in metro Boston. After a wet storm, look at the deck the next day, not the day of.

Is a 1990s deck in Worcester or Pittsfield definitely unsafe? No. It is just statistically more likely to have been sized for 40 psf when the town's Pg is 50 or 60. A lot of older decks were quietly over-built. The only way to know is a structural inspection that compares the actual joist size and spacing against the right span table for the town's Pg.

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Get a real number on your deck

A handful of questions decide whether your deck is over its design snow load: when it was built, which town it sits in, and whether the original builder used the right table. None of that is visible from above. If you are in a 50 or 60 psf town and your deck predates October 2024, a structural look from a Massachusetts deck contractor (one who builds to the 10th edition R507 tables, not DCA-6 by habit) is the cleanest way to find out.

Tell us your town, your approximate deck size, and when it was built and get a free estimate from a Massachusetts deck contractor. We will route the request to licensed deck builders in your area who handle structural assessments and reinforcement work, not just board replacements. You will get quotes for the actual fix, sized to your town's actual snow load.

For an overview of all deck and porch work in the state, visit the Massachusetts decks and porches hub.