Deck cost per square foot in Massachusetts: real Boston numbers for wood and composite
Deck cost per square foot in Massachusetts from 2025 Boston data: about $64 for wood and $81 for composite, plus footings, permits and railing code.
Mateus MagnoLicensed Construction Supervisor · November 2, 2026 · 4 min read
Using Remodeling magazine's 2025 Cost vs. Value data for Boston, a 16x20-foot deck costs about $64 per square foot in pressure-treated wood ($20,594) and about $81 per square foot in composite ($25,806). Height, 48-inch frost footings, stairs and railings move most Greater Boston decks above or below that.
What does a deck cost per square foot in Massachusetts? Using the 2025 Cost vs. Value figures for Boston, a 16x20-foot deck works out to roughly $64 per square foot in pressure-treated wood and $81 per square foot in composite. Below I show where those numbers come from and what pushes a Somerville or Cambridge deck above or below them.
Short version: size matters, but height, footings, stairs and railings matter just as much on our tight Greater Boston lots.
Deck cost per square foot: the 2025 Boston numbers
Remodeling magazine's 2025 Cost vs. Value report for Boston prices two deck projects. Both are the same 16x20-foot (320 sq ft) deck: treated joists on 4x4 posts and concrete piers, a built-in bench and planter, three steps to grade and a full railing (see the wood deck spec and the composite deck spec).
| Boston, 2025 | Wood deck | Composite deck |
|---|---|---|
| Job cost | $20,594 | $25,806 |
| Cost per sq ft (my math, 320 sq ft) | about $64 | about $81 |
| Resale value | $13,664 | $18,698 |
| Cost recouped at resale | 66.4% | 72.5% |
Two things stand out. Composite costs about $5,200 more on this model deck, but it also holds more of its value at resale. And neither version pays for itself, so a deck is mainly a quality-of-life project.
What pushes a Massachusetts deck above the average
The model deck is low, simple and three steps off the ground. Most decks I build in Somerville, from Teele Square to East Somerville, are not. Here is what moves the price:
- Height. A second-floor deck needs taller posts, bigger beams, more stairs and longer railing runs.
- Footings. Attached decks here usually need deep frost footings (more below), and digging four feet down by hand takes time.
- The house side. In 1900 to 1930 houses I often find a rotted or missing band joist where the ledger needs to go. That repair comes first.
- Stairs and railings. A long stair run or a premium rail system can cost as much as the decking itself.
- Access. On narrow Somerville lots, every board and bag of concrete goes in by hand down a side path or driveway.
- Lead-safe work. If we disturb painted trim or siding on an older house, the job follows lead-safe rules. My lead paint guide explains what that means.
Permits and City fees in Somerville
Almost every deck here needs a building permit. Under the Massachusetts residential code (R105.2), a deck is exempt only if it is 200 sq ft or less, no more than 30 inches above grade, not attached to the house and not serving a required exit door. Somerville's ISD Building Division requires a permit for all interior and exterior work except painting, tiling and flooring.
Fees come from the City's building fee schedule:
- $20 per $1,000 of estimated cost (up to $100,000).
- $4 per $1,000 for building code plan review.
- A safety review fee of 0.35% of the cost, minimum $100.
- A flat $250 when zoning review is needed.
On a $25,806 composite deck, that is roughly $720 in building-side fees, or about $970 with zoning review. Setbacks are usually the bigger hurdle on small lots. My Somerville deck permit guide walks through zoning, drawings and inspections.
Footings and frost depth
- Under IRC R507.3, deck footings must sit at least 12 inches below undisturbed ground.
- If the deck is attached to the house, the footings must be protected from frost, typically by extending below the frost line.
- Massachusetts sets that frost line at 48 inches in its residential code amendments.
- The ledger must be at least a 2x8 treated board and can never hang on stone or masonry veneer (R507.9.1.1).
- With the code's standard lateral detail, you need two hold-down devices rated at least 1,500 lb each, within 24 inches of each end of the deck (R507.9.2).
Railings and stairs: the code basics
- Guards are required where the deck is more than 30 inches above grade. They must be at least 36 inches tall, with no opening that passes a 4-inch sphere (IRC R312).
- Stairs: Massachusetts allows risers up to 8 1/4 inches and requires treads of at least 9 inches.
- Handrails are required on any flight with four or more risers, set 34 to 38 inches high (R311.7.8).
- Stair width: at least 36 inches clear above the handrail (R311.7.1).
These are the one- and two-family rules. A triple-decker's stacked porches fall under the base building code, which my porch and stair safety guide covers.
Need a hand?
I design, permit and build decks across Somerville, Cambridge and Medford. Book a free walkthrough and I will measure, check zoning and send a written line-item budget, usually within 48 hours.
Frequently asked questions
How much does a 16x20 deck cost in Massachusetts?
The 2025 Cost vs. Value report puts a 16x20-foot deck in Boston at $20,594 in pressure-treated wood and $25,806 in composite. Higher decks, long stairs or premium railings cost more.
Is a composite deck worth it in Boston?
In the 2025 Boston data, a composite deck recouped 72.5% of its cost at resale versus 66.4% for wood. It costs about $5,200 more up front on the same size deck.
How deep do deck footings need to be in Massachusetts?
Footings must be at least 12 inches below undisturbed ground, and footings for a deck attached to the house must be frost-protected. Massachusetts sets the frost line at 48 inches.
Do I need a permit to build a deck in Somerville?
Almost always. The state exempts only decks of 200 sq ft or less that are no more than 30 inches above grade, not attached to the house and not serving a required exit door.
Planning work on your home? See everything I do, how I price work and the towns I work in.
Mateus Magno founded Magno & Co in 2020. He is a licensed Massachusetts Construction Supervisor (CS-123658), registered Home Improvement Contractor (HIC #220484) and certified Lead-Safe Renovator Supervisor who has renovated and managed over $5 million in projects across Greater Boston.
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