Three-season Porch - Part 3 of 4

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Three-season porches add living space to your home. Typically, they are wired with lights and electrical service, but they are not hooked into your heating and cooling system.


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A three-season porch blends indoor comfort with an outdoor atmosphere. It is a transition space between your home and yard. Windows with self-storing screens line each wall to provide plenty of fresh air and an enjoyable view of your landscape, while keeping insects and inclement weather at bay.
Building a three-season porch is an ambitious project, but like any large-scale project, it can be divided into simple, manageable steps, making the construction process less daunting. Because each building situation is different, you’ll need to create your own plans and plan drawings to reflect the specific details and dimensions of your home and yard. For example, the distance from the ground to your home’s entrance will vary, affecting the height of the deck frame posts and the steps and landing. Make sure all plans comply with your local building codes and zoning laws. You will need to submit complete plan drawings, including an elevation drawing and a floor plan, along with an estimated cost of materials in order to be issued a building permit.

What You'll Need


Circular saw
Caulk gun
Power auger or clamshell digger
Reciprocating saw
Hand tamper
Power miter saw
Hammer drill


2 x 2s
2 x 4s
Lag screws
Joist hangers
Post anchors
Angle brackets
Hurricane ties
Common nails
Joist-hanger nails
Box nails
Siding nails
Roofing nails
Finish nails
Deck screws
Masonry screws
2 x 4 trusses (8-in-12 pitch)
Silicone caulk
Construction adhesive
Roofing cement
15# building paper
Compactible gravel
12"-dia. concrete footing forms
Asphalt shingles
Windows with self-storing screens
Combination storm door and threshold
12 x 12" aluminum louvered


Step 1

How to Build a Three-season Porch

Use metal H-clips (inset) between sheets to ensure a 1⁄8" gap at horizontal seams, and leave a 1⁄4" gap at the peak.

Step 2

How to Build a Three-season Porch

Attach the fascia. Use a speed square to mark one end of the two 1 x 6 gable fascia boards to match the roof pitch. Cut the peak ends, then measure and cut each board long enough to extend several inches past the ends of the rafter tails. Position the fascia boards so the top edges are flush with the sheathing. Fasten the fascia with 8d galvanized finish nails. Cut side fascia boards to length and install so the tops of the boards do not project above the sheathing. Trim the ends of the gable fascia boards so they are flush with the side fascia boards.

Step 3

How to Build a Three-season Porch

Install the roof covering. Cut away the house siding about 2" above the roof sheathing. Install drip edge flashing at the eaves and then staple overlapping courses of 15# building paper to the roof deck, starting at the eaves. Install drip edge along the gable ends then shingle and complete the flashing. If you have not installed roof coverings before, refer to a roofing book for more information.

Step 4

How to Build a Three-season Porch

Attach the wall sheathing and housewrap. Attach 1⁄2" exterior-grade plywood sheathing to the porch framing, using 2" deck screws or 6d box nails driven every 6" along the edges and every 12" in the field area. Make sure all seams fall on studs. Apply house wrap or 15# building paper in horizontal strips over all of the wall surfaces using staples spaced roughly 12" apart. Also wrap the framed door and window openings with building paper or self-adhesive window flashing.

Step 5

How to Build a Three-season Porch

Attach the window sills. Cut 1 x 2 sill nailers for the end wall, side wall, and door wall. Align each nailer flush with the interior edge of the rough sills and fasten it with 4d box nails. Cut 2 x 8 window sills and install them in the rough openings so they slope downward and their back edges extend out 1" past the interior edges of the rough openings. Fasten the sills with 16d galvanized finish nails.

Step 6

How to Build a Three-season Porch

Install the windows. At each window rough opening, install nailers 1" from the inside edges of the framed openings to create installation surfaces for the windows. Use 2 x 2 for the horizontal nailers and 1 x 2 for the vertical nailers. Place the combination storm windows against the nailers so the flanges are roughly 3⁄4" from the framing members of the walls. Make sure all windows are plumb, then fasten them to the nailers using the screws specified by the window manufacturer. Run a thick caulk bead between the windows and the sills.

Step 7

How to Build a Three-season Porch

Frame the door opening. Measure, mark, and cut finish-grade 1 x 6 lumber to size for the door jambs. Rip the pieces to width, if necessary. Install the jambs for the door header and the latch flush with the sheathing using 8d casing nails. For the hinge-side jamb, align flush with sheathing and shim as necessary so that the door opening is 1⁄8" to 1⁄4" wider than the door itself.

Step 8

How to Build a Three-season Porch

Install the door. Note: Read and follow the manufacturer’s instructions for your storm door before installation. Position the door in the framed opening so the hinge side of the door is tight against the door jamb. Drill guide holes spaced every 12" through the hinge-side frame and into the sheathing. Attach the frame with mounting screws (provided with door). With the door closed, drill guide holes and attach the latch-side frame to the sheathing. Keep an even gap between the door and the frame. Center the door frame top piece on top of the frame sides. Drill pilot holes and fasten it to the door header. Attach lock and latch hardware as directed.

Step 9

How to Build a Three-season Porch

Install the soffit panels. Cut soffit panels to size from 1⁄4" exterior-grade plywood. Install the panels at the gable-end overhang first, then along the side wall and door wall eaves. Hold each panel flush against the lookouts or rafter tails, with the front edge tight against the fascia boards, and fasten using 4d galvanized casing nails.

Step 10

How to Build a Three-season Porch

Install the trim. Measure and cut the inner window trim for each window from 1 x 2 cedar, beginning with the horizontal pieces at the header. Install them flush with the exterior face of the wall sheathing, with the back edges against the window flanges using 4d galvanized finish nails. Cut the corner trim pieces so they extend from 1" below the bottom edge of the wall sheathing up to the soffits. Rip the boards to width if necessary and notch them to fit around the window sills. Fasten them with 8d galvanized finish nails. Cut the end trim to fit from 1" below the bottom edge of the deck frame up to the soffits. Fasten with 8d galvanized finish nails. Cut the horizontal trim pieces (the header trim, sill trim, and skirt trim) and nail in place. Cut and install the vertical window trim. Finally, install the aluminum door threshold.



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