A screened porch contractor on Cape Cod is really building three things at once: a deck that will not heave in sand, a roof that has to tie into a Cape roofline without leaking, and a screen wall that has to survive a nor’easter and ten summers of salt air. Get any one of them wrong and the porch becomes the room nobody uses. Get all three right and it is the room the whole house gathers in from May through October.
Coast Carpentry Home Group builds screened porches on Cape Cod homes as part of our deck installation on Cape Cod and our home additions on Cape Cod, from our shop at 14 Parker Rd, Unit A in Osterville. Our crews pour the footings, frame the floor and roof, flash it into the cedar shingles and set the screens, so one team owns the whole thing. This is how we build one on a Cape house, what the lot and the town will let you do, and the handful of details that decide whether the screens are still tight in year ten.
Key takeaways
- A screened porch on Cape Cod sits on piers that reach below the 48 inch frost line, and in Cape sand we widen the footing at the bottom so the pier does not sink or lift with the seasons.
- The hardest part of a porch on a one story Cape is the roof. A shed roof hung under the eave is often too flat to shingle, so we raise it into the main roof or turn it into a gable, and we decide that before anything else.
- Screens on a windward side of a Cape house need a fixed frame or a spline track system, fiberglass or stainless mesh, and a screen door on the lee side. Aluminum mesh pits and tears within a few seasons of salt haze.
- Every bracket, hanger, screw and hinge on a porch within sight of salt water is stainless or hot dip galvanized. The copper in modern treated lumber eats ordinary plated hardware.
- A screened porch needs a building permit in every Cape town, Conservation review if it sits within 100 feet of a wetland or the shore, and Old King’s Highway approval on the north side of Route 6A. It does not add a bedroom, so it does not trigger a Title 5 upgrade.
What is a screened porch on a Cape house, and how is it different from a deck or a sunroom?
On the Cape the three live on a sliding scale. A deck is the cheapest way to get outside and the one that sees the least use in July, because the greenheads and the no-see-ums own the evening near any marsh in Falmouth, Mashpee or Sandwich. A screened porch is the same floor with a roof and a screen wall, and it is the one that actually gets used from dinner through dark. A three season room is that porch with glass instead of screen, which keeps the wind out in October and April and adds a month on each end.
We build all three and we steer owners between them on how they live, not on what sells. A family that eats outside every night from Memorial Day to Columbus Day wants the screened porch. An owner who wants to sit out there in a sweater in November should read our guide to a sunroom addition on Cape Cod first, because the framing decisions for glass are different from the framing decisions for screen and it is cheaper to make them once.
Where does a screened porch go on a Cape lot, and what does the town allow?
The lot decides more than the owner expects. Every town on Cape Cod has side and rear setbacks for a roofed structure, and a screened porch is roofed, so it counts the way an addition counts, not the way an open deck sometimes does. On the small village lots in Hyannis, Dennis Port and West Yarmouth that can take the whole back yard off the table. We pull the zoning for the parcel and draw the buildable envelope before we draw a porch.
Water is the second line. If any part of the lot is within 100 feet of a marsh, a pond, a bank or the shore, the porch goes in front of the Conservation Commission under the Wetlands Protection Act before the building department will issue a permit. We file that paperwork for owners in Cotuit, Popponesset and along the Bass River all season, and it is routine when it is filed early and a headache when it is discovered after the footings are dug. On the north side of Route 6A from Sandwich to Orleans, the Old King’s Highway committee reviews anything visible from the road, and a porch on the street side of a Cape in Barnstable Village or Yarmouth Port needs their certificate first.
Then the practical side. Afternoon sun off Nantucket Sound bakes a south facing porch in August, so a deep overhang or a taller west knee wall helps. The prevailing southwest wind is what cools the porch and what drives the rain in, so it decides which wall gets the sturdiest frames. The view is last, and it usually wins anyway.
How do we build footings for a screened porch in Cape Cod sand?
Cape soil is sand with a little loam on top, and sand drains so fast that people assume frost is not a problem. It is. Water sits in the sand above the hardpan in a wet winter and it heaves whatever is sitting in it. A deck pier set two feet down in Marstons Mills moves every spring. A pier at four feet with a footing spread wide enough for the load does not, and the building inspector in every Cape town will ask to see the hole before the concrete goes in.
The roof changes the math. A deck carries people and furniture. A screened porch carries that plus a roof full of February snow and a wind trying to lift it, so we size the footings for the roof load, keep the piers tighter than we would on an open deck and tie the posts to the piers with hardware that resists uplift as well as weight. Near the water, where the sand is loose and the water table is close, we have used helical piers that screw down to bearing instead of poured footings, and we say so on the plan rather than hoping a sonotube holds.
How do we attach the porch to the house without rotting the wall?
The ledger is where most old Cape porches fail, and it fails the same way every time: someone nailed a board over the shingles, never flashed it, and twenty years of wind driven rain ran down the wall into the rim joist. We take the shingles off in that band, check the sheathing and the rim with an awl, and only then bolt the ledger. The flashing laps over the ledger and under the water barrier above it, so water that hits the wall goes out over the porch, not behind it. Our guide to white cedar shingle siding on Cape Cod shows the same weave and flashing sequence at a wall.
Some houses should not get a ledger at all. A cantilevered bay, a wall with brick or stone veneer, a rim joist that is soft, or an older house where the floor framing runs the wrong way. In those cases the porch gets its own beam and posts a few inches off the house and the roof does the tie in. It is a little more concrete and a lot less risk.
How does a porch roof tie into a Cape Cod roofline?
This is the detail that separates a porch that looks like it was always there from one that looks bolted on. A classic Cape has its eave at about eight feet. Hang a shed roof under that eave, keep seven feet of headroom at the door, and by the time you reach the outer edge of a twelve foot porch there is no pitch left. Asphalt shingles need real slope to shed water, and a roof flatter than that will leak at the first ice dam.
So we do one of three things. We open the main roof above the porch, frame the porch rafters up into it and flash the joint, which gives a steeper porch roof and ties the two together under one run of shingles. We build a gable instead of a shed, which meets the house at a ridge, looks right on a Cape, and sheds snow off both sides. Or, where the owner wants a low profile and the view over the roof matters, we run a rubber roof at a gentle slope and handle it as flat roofing, which is the same work we do on the mudroom additions on Cape Cod we tuck under an eave. The shingled versions get the same CertainTeed shingles and ice and water shield at the eave as the main roof, and the whole thing carries our lifetime workmanship warranty.
Which screen system holds up to salt air and a nor’easter?
Screens are where the cheap porch shows itself. Mesh stapled to the framing and covered with a batten looks fine in June and starts to pull loose and sag by the second October, because the wind loads the whole panel and a staple line cannot hold it. A framed panel, sized to the bay and set into a stop, spreads that load to the frame. A spline track system does the same with a rubber spline in an extruded channel, and it is what we use when the owner wants to re-screen a panel in ten minutes instead of an afternoon.
| Mesh | How it behaves in Cape salt air | Where we use it |
|---|---|---|
| Fiberglass, standard 18 by 16 weave | Does not corrode, does not dent, dims the view a little. The easiest to replace. | Most porches, especially inland and on the lee side. |
| Fiberglass, no-see-um 20 by 20 weave | Tighter weave that keeps out the biting midges off the marshes. Cuts airflow a bit on a still night. | Any porch near a salt marsh, a creek or the shore in Falmouth, Mashpee, Sandwich or Barnstable. |
| Stainless steel | Strongest, clearest view, shrugs off salt and dogs. Costs the most and is harder to spline. | Waterfront porches, the windward wall, and anywhere a big dog leans on the screen. |
| Aluminum | Clear and cheap, but it pits, dulls and goes brittle in salt haze and creases if a chair hits it. | We do not use it on Cape porches within a mile of salt water. |
Two details matter as much as the mesh. The screen door goes on the lee side of the porch so the summer southwest wind is not trying to blow it open every afternoon, and it gets a kick plate and a closer so it is not slamming in a gust. And every panel on the windward side is removable, so an owner in Chatham or Dennis can pull them before a hurricane watch and put them back the next morning instead of buying new ones.
What hardware and fasteners do we use near salt water?
Salt air finds every short cut. A deck screw with a thin zinc coat looks fine for a summer and then bleeds rust onto the decking. A bright hanger on a treated joist turns to lace in a few years because the copper in the lumber and the steel in the hanger make a battery once they get wet. On a porch in Hyannis Port, Falmouth Heights or Harwich Port we spend the money on stainless at the connections and galvanized hardware rated for treated lumber everywhere else, and the porch is still tight when the house changes hands.
The same goes for the screen door hinges, latch and closer. Cheap screen door hardware is plated pot metal and it seizes. We use stainless or solid brass, and we tell owners a brass latch will turn brown long before it fails.
What do we build the porch floor, knee wall and ceiling out of?
A screened porch floor gets wet. Rain comes through screen in a sideways storm no matter how tight the panels are, so we lay the decking with gaps like a deck and pitch the framing slightly away from the house. Composite boards are what most owners choose for the no maintenance, and the same board choices we walk through in our guide to composite deck installation on Cape Cod apply here, with the one difference that a roofed floor stays cooler and shows less fade. Mahogany is the traditional choice and it is beautiful under a roof, where it keeps its color longer than it does on an open deck. Owners who want the lowest upkeep should read our notes on building a low maintenance deck on Cape Cod before choosing.
The knee wall is what makes the porch feel like a room and what keeps the mesh out of reach of lawn mowers, dogs and snow. We frame it at about thirty inches, run the house’s own white cedar shingles on the outside so the porch reads as part of the house from the yard, and finish the inside with painted beadboard. The ceiling gets beadboard too, a fan on a damp rated box, and a couple of outdoor outlets, all on a permitted circuit run by a licensed electrician.
Should you build a screened porch or a three season room instead?
This is the one question we ask every owner before we draw anything, because the answer changes the framing. A porch built for screen has wide bays and light framing at the openings. A room built for glass needs headers sized for window units and openings framed to a window size, and converting a screen porch later means reframing every bay. Some owners split the difference with interchangeable panels, screen in summer and clear panels in the shoulder seasons, and that is a fine answer as long as the openings are built to a panel size from the start.
The honest version of when not to hire us for a porch: if what the owner really wants is a heated room with a year round couch, a screened porch is the wrong building and a four season room or a proper addition is the right one. We have talked more than one family out of a porch and into an addition, and more than one out of an addition and into a porch, because the porch was what they would actually use.
What drives the cost of a screened porch on Cape Cod?
We do not publish prices because no two Cape porches are the same job. A twelve by sixteen porch off a ranch in South Yarmouth with a shed roof, fiberglass screens and composite decking is a straightforward build. The same footprint on a shingle style house in Osterville with a gable roof tied into the main roof, stainless mesh, mahogany floor, a Conservation filing and a committee hearing is a different job with the same name. Our guide to what a new deck costs on Cape Cod walks through the deck side of the math, and the roof and screens sit on top of that.
What we can tell you on the phone is which of those factors apply to your house, and after a site visit we give you a written number for the whole job, permits and filings included. Ask for a quote through our contact page and we will come look at the spot.
Start with the spot on the lot, not the furniture
The porches we are proudest of started with a walk around the yard: where the wind comes from, where the sun lands at six o’clock, where the setback line is and where the view is. The screens, the floor and the fan come after. If you are in Barnstable, Falmouth, Mashpee, Sandwich, Yarmouth, Dennis, Harwich or anywhere else on the Cape and you want a porch you will actually sit in, our crews have built them on the same sandy lots and in the same salt air for more than 25 years. Read what our customers say on our reviews page, then have a look at our deck builder guide for Mashpee for how we handle the lots near the Sound.
Ready to plan a screened porch?
Coast Carpentry Home Group builds screened porches, decks and additions across Cape Cod from Osterville. Tell us about your house and the spot you have in mind on our contact page, or see the rest of our deck installation services on Cape Cod.
Frequently asked questions
Do I need a permit to build a screened porch on Cape Cod?
Yes. A screened porch has a roof and attaches to the house, so every Cape town treats it as a structure that needs a building permit, with an electrical permit for the fan and outlets. Add a Conservation Commission filing if the lot is within 100 feet of a wetland or the shore, and Old King’s Highway review if the porch is visible from Route 6A on the north side. We pull all of it as part of the job, and the Barnstable Building Division page is a good example of what a town asks for.
Can you screen in an existing deck?
Sometimes. The deck has to be on frost depth piers sized for a roof, with a sound ledger and framing that will carry the extra weight. Most older Cape decks were built on shallow piers for people and furniture, not a roof full of snow, so screening one in usually means new footings under the existing frame or a new frame. We look at the piers and the ledger first and tell you which it is.
How long does it take to build a screened porch on Cape Cod?
Once the permit is in hand, a typical porch takes a few weeks of on site work, from footings through screens and paint. The permit and any Conservation or historic district review take longer than the build, which is why we start that paperwork in the winter for porches owners want to use by summer. A porch that cuts into the main roof or needs helical piers takes longer than one with a shed roof on poured piers.
Can a screened porch be turned into a three season room later?
Yes, if it was framed for it. We size the openings and headers to window units when an owner thinks glass might come later, so the conversion is a matter of setting the units and trimming them out. A porch framed only for screen has wide bays that need reframing before glass can go in, which is why we ask the question before we build.
Does a screened porch count as living space or trigger Title 5?
No. A screened porch is unconditioned space and does not add a bedroom, so it does not change the bedroom count the septic system was sized for and it does not trigger a Title 5 upgrade. It does count toward lot coverage in most Cape towns because it has a roof, which is the number to check before you fall in love with a size.
We serve Cape Cod, Massachusetts
Coast Carpentry Home Group works across all 15 Cape Cod towns, from Bourne out to Provincetown. We do not take projects outside the Cape.
On the Cape and looking for an estimate? Call (508) 360-9658 or send us a message.
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