How to build a screened porch

Choose the kind of screened porch first

"Screened porch" covers two quite different builds, and the choice changes the whole project:

• A raised screened porch has its own floor framing on footings, a roof and screened walls. It is built like any porch: Inver Grove Heights, Minnesota, requires the floor to carry a 40 pound per square foot live load plus a 10 pound per square foot dead load^[1].
• A screen enclosure on a patio slab is a roof on posts with screens between them. It falls under the patio cover rules: one story, 12 feet at most, with the longer wall and one more wall at least 65 percent open below 6 feet 8 inches, filled with insect screening, thin approved plastic or code-compliant glass^[4].

Screening an existing deck is the third route, and it is still a new porch for the city: Mound requires a building permit to convert an existing deck into a porch^[7]. Porch footings must be sized to carry all the roof and floor loads^[1], so plan on the deck's footings and beams being checked against the new roof, not just reused.

Look at the house wall before you design

A screened porch covers windows and doors, and the code cares where they lead. In Minneapolis, a bedroom's required emergency escape window may not open onto a screened porch, and bathroom windows that open onto a screened or enclosed porch no longer count for natural ventilation^[3]. Windows needed only for light and ventilation may open onto a patio-type structure that keeps the 65 percent openness rule^[3]. Golden Valley warns that a porch addition may affect the emergency egress and the natural light and ventilation requirements of the rooms it is attached to^[5].

Materials

• Footings: concrete, sized for the roof and floor loads^[1].
• Framing: approved decay-resistant or treated wood wherever the framing is left exposed^[1].
• Fasteners in treated wood: hot-dip zinc-coated galvanized steel, stainless steel, silicon bronze or copper^[1].
• Roof: rafters with collar ties or a ridge beam, or engineered trusses, sheathing, flashing and roofing^[1].
• Screens, screen doors, and tempered glass wherever glazing is in a hazardous location^[1].

Step by step

Lay out the porch and check the setbacks

Mark the porch on your certificate of survey and on the ground. New Prague treats screen and three-season porches as part of the house for zoning: they must meet the setbacks for principal structures in the district^[2].

Dig and inspect the footings

Footings go at or below the minimum frost depth, 42 inches in Inver Grove Heights, and are sized to carry the roof and floor loads^[1]. The inspector sees them after the holes are dug and before the concrete is poured^[1]. Hawthorn Woods, Illinois, goes further and requires a continuous concrete foundation for screen porches connected to the house^[6].

Frame the floor

Set the beams on the posts and footings, then the joists. Floor boards depend on joist spacing: 2-inch decking at 24 inches on center, 5/4 inch decking at 16 inches on center^[1]. A cantilevered floor of the house may not carry the porch without special structural design^[1].

Raise the posts and headers

Frame the walls as posts with headers over the screened openings. The headers are sized on your cross section: Inver Grove Heights asks for the header sizes supporting the window and screened openings^[1].

Frame the roof and flash it

Rafters without ceiling joists, as in a vaulted porch ceiling, need collar ties or a ridge beam supported by a wall or girder truss^[1]. Install step and kickout flashing wherever the porch roof meets a vertical wall of the house^[1]. If you use engineered trusses, keep the truss layout and specifications for the plan reviewer^[1]; Hawthorn Woods requires them signed and sealed by an engineer^[6].

Call the framing inspection

Wiring goes in first: when the porch has electrical work, the rough-in is inspected before the framing inspection^[1][2]. New Prague notes that electrical work needs its own permit^[2].

Build the guard and the stairs

Screens are not a guard. Inver Grove Heights and New Prague both state that screening alone is not an approved guardrail^[1][2]. Where the floor is more than 30 inches above grade, build a guard at least 36 inches high with openings a 4-inch sphere cannot pass^[1]. Stairs need treads of at least 10 inches, risers of 7 3/4 inches at most, uniform within 3/8 inch, and a width of at least 36 inches^[1]. A landing is required at the top of exterior stairs with a total rise over 30 inches, except on screen porches where the only door at the top is a screen door that does not swing out over the stairs^[1].

Hang the screens and the doors

Fit the screens in the openings once the framing is approved. On a slab enclosure, keep the openness rule in mind: insect screening, approved plastic no thicker than 0.125 inch, or code-compliant glass^[4].

Pass the final inspection

The final comes when the structure is complete^[1]. Until then, the stamped plans and survey stay on site and the inspection record card stays posted on an exterior wall of the porch^[1].

Mistakes to avoid

• Counting the screens as the railing^[1][2].
• Putting a bedroom's escape window behind the porch^[3].
• Screening a deck without checking its footings for the new roof^[1][7].
• Leaving out the kickout flashing where the roof meets the house wall^[1].
• Adding windows and heat later without asking: Golden Valley may require energy calculations for spaces that will be heated^[5].

Do you need a permit to build a screened porch?

Yes. Minneapolis requires building permits for all porches, screen porches included^[3], and Hawthorn Woods requires a permit before any screen porch construction^[6]. The screened porch permit page lists what the application contains, the inspections and real fees.

How we can help

With the All-in offer, the paperwork side is done for your address: the city's porch rules with links, the survey-based site plan, the floor plan, section and elevations for the permit application, the forms and the fee, then our team's review and follow-up until the permit is approved. You build the porch.

Common questions