Three-season Porch - Part 2 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 dril


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 vent


Step 1

How to Build a Three-season Porch

Lay out wall frames. Use a pencil and a speed square to begin marking the wall stud locations on the sole plates and the cap plates for the porch walls.

Step 2

How to Build a Three-season Porch

Include marks for extra corner studs in walls that will butt up against another wall.

Step 3

How to Build a Three-season Porch

Build headers. Construct headers by sandwiching together pairs of 2x lumber with a piece of 1⁄2" plywood in the middle. This will create strong beams that are the same thickness as dimensional lumber (31⁄2"). Use construction adhesive and 10d common nails to fasten the beam members together.

Step 4

How to Build a Three-season Porch

Frame the walls. Assemble the walls one at a time using 16d common nails for endnailing and 10d common nails for toenailing. Use 8d box nails to fasten the 2 x 4 blocking between the king studs and the common studs at the ends of the walls. Raise the walls one at a time and brace them with 2 x 4s staked to the ground. Begin with the side wall, followed by the door wall, and finally the end wall. Make sure each wall is plumb, then fasten it to the floor frame with 16d common nails spaced every 16", but do not nail through the bottom plate in the door's rough opening. Tie the walls together and to the house with 16d common nails.

Step 5

How to Build a Three-season Porch

Install the first truss. Locate the framing members of the house and draw reference lines on the outside wall up to the planned roof peak. With help, hoist the first truss into position against the house. Align the peak of the truss with the centerline marked on the siding. The truss should be flush against the siding and the rafter tails should overhang the top plates equally. Nail the chords of the truss to the framing members of the house using 20d common nails.

Step 6

How to Build a Three-season Porch

Install the remaining trusses. Lay out the remaining truss locations every 16" on-center on the top plates of both the side wall and the door wall. Lift the remaining trusses into place and install them, working away from the house. Make sure the rafter tails overhang the top plates equally. Toenail through the bottom chords with 10d common nails to fasten.

Step 7

How to Build a Three-season Porch

Reinforce the trusses with hurricane ties attached by driving 8d common nails into the top plate and 8d joist-hanger nails into the rafter chords.

Step 8

How to Build a Three-season Porch

Build the gable wall. On the top plate of the end wall, mark the gable wall stud locations every 16" on center. Set the two 2 x 4 gable plates on edge and use a speed square to mark the pitch for the peak at one end. Cut the peak ends and fasten with 10d common nails. Transfer the stud layout marks from the end wall to the gable plates. Cut the gable wall studs to length, trimming the top ends to match the roof pitch. Toenail the studs to the end wall and endnail through the gable plates using 10d common nails.

Step 9

How to Build a Three-season Porch

Build the gable overhang. From the peak of the gable-end truss, measure down along each rafter chord and mark the lookout layout. Use a speed square to transfer the marks to the faces of the rafter chords. Transfer the lookout locations to the top of the gable plates. Cut 2 x 4 lookouts and align them with the location lines. Fasten them to the rafter chords and gable plates with 10d common nails. At the peak, fasten a lookout so it’s plumb and the corners are flush with the top edges of the rafter chords. Cut barge rafters to fit and attach them to the ends of the lookouts.

Step 10

How to Build a Three-season Porch

Install the roof sheathing. Cut 1⁄2" exterior-grade plywood or oriented-strand board sheathing to cover the trusses and the gable overhang. Install sheathing from the rafter tails to the peak, using 8d box nails driven every 6" along the edges and 12" in the field of the sheets. The sheathing should not protrude beyond the rafter tail ends, and any seams should fall on rafter chords.



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