Short answer
Appendix AY of the 2022 Connecticut State Building Code gives every municipality an ultimate design wind speed and a ground snow load. In the towns we serve those are 120 or 125 mph for wind and 30 or 35 psf for snow. Together they determine how the roof covering has to be fastened and how the structure has to carry load.
On this page
Two numbers govern how a roof gets built in Connecticut, and most homeowners never hear either of them. They come from Appendix AY of the 2022 Connecticut State Building Code, which assigns every municipality in the state an ultimate design wind speed and a ground snow load.
They are not trivia. They decide how the roof covering is fastened, what the structure has to carry, and whether the wind warranty on your shingles is valid.
Number one: design wind speed
The design wind speed, written Vult, is the wind the structure is designed to survive. Across the fifteen towns we serve it is either 120 mph or 125 mph.
| Design wind speed | Towns |
|---|---|
| Design wind speed125 mph | TownsGuilford, Madison, New Haven |
| Design wind speed120 mph | TownsAvon, Fairfield, Farmington, Glastonbury, Greenwich, Hartford, Manchester, Middletown, Simsbury, Stamford, West Hartford, Westport |
The distribution surprises people. Guilford, Madison and New Haven sit at 125 mph — higher than Greenwich, Stamford, Westport and Fairfield, which are all 120 mph despite fronting Long Island Sound. Proximity to New York has nothing to do with it. Exposure to open water along the central shoreline does. Old Saybrook, where we are based, is 126 mph.
Every town on that list is inside a designated hurricane-prone region.
What it changes on your roof
A shingle carries a wind rating, but that rating is conditional. It is only valid if the shingle is fastened the way the manufacturer requires in order to earn it. For high-wind coverage most manufacturers specify six nails per shingle inside a defined nail zone, instead of the standard four.
That is the practical consequence. A four-nail install on a 125 mph coastal house is faster and cheaper, and it will not carry the coverage the homeowner thinks they bought.
One trap worth knowing
You will sometimes hear that a house over 110 mph triggers additional high-wind underlayment requirements. That threshold is keyed to Vasd — the nominal, allowable-stress design wind speed — not to Vult. In the towns we serve Vasd works out to roughly 93 to 97 mph, comfortably under 110. So the trigger does not apply here.
It is an easy mistake because both numbers are "wind speed in mph" and they differ by about 30. Getting it wrong in either direction costs the homeowner money.
Number two: ground snow load
Ground snow load, written pg, is the weight of snow the roof structure is designed to carry, in pounds per square foot.
| Ground snow load | Towns |
|---|---|
| Ground snow load35 psf | TownsAvon, Farmington, Simsbury |
| Ground snow load30 psf | TownsEvery other town we serve |
Avon, Farmington and Simsbury carry the higher figure. Sitting up against the ridge on the west side of the Farmington valley is why — that terrain holds snow, particularly on north-facing slopes, long after it has gone elsewhere.
What it changes
Snow load is structural. It governs rafter and truss sizing, and it matters most on additions, dormers, porch roofs and anywhere a roof plane was extended by a previous owner without an engineer looking at it.
For a straight replacement on an existing, sound structure it usually changes nothing. Where it bites is when a roof is being altered, or when a heavy material is going on a structure originally framed for a light one. Putting slate or cedar on a house framed for asphalt is a structural question in a 35 psf town, not a preference.
Why a state average is not good enough
A contractor working off a statewide rule of thumb rather than your town's actual figure lands in one of two places. Either they over-specify, and you pay for detailing your house does not need. Or they under-specify, and the manufacturer has grounds to decline a wind claim later.
Neither is a hypothetical. The figures are published, per municipality, in a table anybody can look up. Ours are on the roofing page, covering all fifteen towns, and each town's own page carries its own numbers — Guilford and Madison at 125 mph, Avon and Simsbury at 35 psf, and so on.
The short version
- Find your town's Vult and pg.
- Make sure the quote specifies a nail count that matches the wind figure.
- Make sure any structural change accounts for the snow figure.
- Do not accept a specification written for "Connecticut" generally.
If you would like the figures for your own address and a written price built around them, ask for an estimate and we will bring both.
