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Roll up your sleeves! A screen porch is a big improvement, but it's also a big
project, one that might consume most of your spare time
this summer. So, we’re keeping this porch design simple.
You can build it with standard dimensional lumber, and
it doesn’t require heavy beams or complex joints. The
simple 2x4 walls are light and airy looking. Two horizontal
bands of 2x4s, set 10 in. from the top and bottom of
the wall, add a design element and stiffen the 2x4 framing
enough to support the hand-built trusses. With this
design, there’s no need to precisely align the overhangs.
And the exposed rafters and open soffit look great on
many house styles.
The total cost of this porch was $6,500, but you could save hundreds of dollars without sacrificing quality by substituting treated decking for the cedar or using tongue-and-groove pine rather than cedar on the ceiling.
Even though it’s a large project, most of the construction is straightforward. If you’ve built decks or sheds, you’ll be able to tackle this job with confidence. In this article, we’ll show you the key steps for building this porch. Study the drawings and photos for more details.
You’ll need a full set of basic carpentry tools, a circular saw and a drill to build this porch. In addition, a reciprocating saw, a table saw and a power miter box will make the job go quicker and give you better results. To reach high places safely and easily, we recommend renting a rolling scaffold system (Photo 8, below) for a month.
Plan ahead to avoid
construction headaches
You can add this porch to almost any house, but attachment
details may vary from what we show here. On most two-story houses, you won’t have to worry about tying in
to the roof, but you may have to situate the porch carefully
to avoid covering a window. The house roof sloped
5 in. per foot (this is called a 5/12 slope) and extended
18 in. at the overhang. Your roof may vary from this, and
the details of how the porch ties in will vary as well.
If you’re not sure how to neatly join the porch and house roofs, we recommend hiring an architect to help work out the details.Another option is to build a full-size mockup of a roof truss out of inexpensive and lightweight 1x4s. Figure out where the top of the wall plate would be if you built the porch according to our plans (Figures A – H). Then support the mocked-up truss at this height to see how the porch overhang meets the roof. If you don’t like the way the overhangs intersect, adjust the level of the deck slightly, alter the wall height or change the width of the overhang.
Contact your local building inspections department to find out what’s required to obtain a building permit. Start this process at least a month before you plan to build. This will allow enough time to work through potential problems.
FIGURE A Porch Plan
Click Image to enlarge.
FIGURE B Deck Framing Plan
Click Image to enlarge.
FIGURE D Ledger
Click Image to enlarge.
FIGURE F Side Wall
Click Image to enlarge.
FIGURE G End Wall
Click Image to enlarge.
FIGURE H Side Wall
Click Image to enlarge.
Click Image to enlarge.
1. Bolt the ledger to the house. Then nail the perimeter
joists together and level and square the assembly.
Measure, cut and set the 6x6 posts.
Click Image to enlarge.
2. Cut the joists to length and nail them into place
with a pair of nails at each end. Then slide joist
hangers onto the end of each joist and nail the hangers.
Click Image to enlarge.
3. Make a mark 1-5/8 in. out from the deck on both
sides. Then make another mark 5-1/8 in. inside the
first mark. Draw plumb lines up from these marks and
cut a 5-1/8-in. slot through the siding but not the
sheathing.
Build the deck square and level
Start by marking the ledger board location on the house
wall. We located the top of the ledger board 90 in. below
the bottom of the soffit. On our house, this left a 6-in.
step down from the patio door to the deck surface.
Remove the siding and attach the ledger with 1/2 x 4-in.
galvanized lag screws (Figure D).Make sure it’s perfectly
level. If the ledger attaches to concrete, predrill holes and
insert lead shield lag screw anchors before installing the
lags. After you mount the ledger, use stakes and string
lines to outline the deck frame according to the dimensions
in Figure B and mark the footing locations. A few
days before you plan to dig the footings, call (888-258-
0808) to have underground utilities marked in the vicinity
of the porch. Your local building department will
specify how large and deep the footings should be for
your climate and soil conditions. Pour a concrete pad in
the bottom of each footing hole after they’ve been
inspected. Let the concrete set overnight.
Next choose the six straightest 2x10s for the perimeter beams. Cut the 2x10s for the two side beams to length and nail the pairs together.Use 16d stainless steel or double- dipped galvanized nails for all of the joist framing and to attach the joist hangers to the ledger board. Rest one end of each side beam in the double joist hangers and prop them up level with a stack of wood (Photo 1). Nail through the joist hangers into the beams at the house to hold them in place. Then connect the opposite ends of the two beams at the front with a 2x10 cut to the same length as the ledger. Adjust the resulting frame until the diagonal measurements are equal. Then brace the frame against stakes pounded into the ground to hold it square while you install the treated posts, joists and decking (Photo 2). Sight along the outside rim joist occasionally and adjust the length of the joists as needed to keep the front rim joist straight.
Cut away the overhang and
siding to make way for the porch
Cut away the overhang and
siding to make way for the porch
If your house has an overhang, you’ll have to cut it back
flush to allow the innermost truss to fit against the wall.
Start by removing the soffit and fascia boards above and
several feet to each side of the deck. It’s easier to remove
extra soffit and fascia boards and patch them back after
the porch is done than to calculate cutoff points now.
After the soffit boards are removed, use a level to
plumb up from the house wall to the underside of the
roof boards, in line with the outside edges of the porch.
Mark the two points. Then drive a long screw or nail up
through the roof boards at the two marks. Snap a chalk line between the nails and remove the
shingles below and about 6 in. above the
line. Chalk a new line and remove nails
along the line. Then saw along the line
and pry off the roof boards (Photo 4).
Be sure to wear safety glasses and hearing
protection when you’re sawing.
Finally, cut off the rafter tails flush to the
house wall.
You’ll have to decide whether to cut a slot where the porch walls meet the siding (Photo 3). If your siding is stucco, brick or stone, you may want to butt the walls to the siding. Photo 3 shows how to cut a slot for the wall. Set the saw blade just deep enough to cut through the siding only. Remove the siding. Waterproof the slot with No. 15 building paper.
Click Image to enlarge.
4. Mark the roof portion that overhangs the deck.
Then cut the roof sheathing back even to the edge
of the house and pry it off. Cut the rafter tails off flush
with the house wall.
Click Image to enlarge.
5. Screw two sheets of plywood to the deck and mark
the truss shape on them (Figure J). Screw stop
blocks along the rafter lines and crosstie line. Assemble
the trusses.
FIGURE J Truss Details
Click Image to enlarge.
Prime and paint the parts ahead of time
Prime and paint the truss parts, wall
frame and screen stops before assembly.
Prime the wood with a special stainblocking
primer such as Zinsser’s oilbased
Cover-Stain. Then brush on a
coat of acrylic exterior house paint.
Make sure to prime every cut end as you
work; otherwise these areas will absorb
moisture and cause staining. We prefinished
the roof boards with an oil finish
(Cabot Clear Solution Natural).
Construct a jig to
assemble the roof trusses
It’s easiest to assemble the roof trusses first, using the
deck platform as a work surface. Screw two sheets of plywood
to the decking and use the dimensions in Figure J
to chalk lines indicating the top of the rafters and the
bottom of the 2x6 crosstie. Cut triangular blocks and
screw them to the plywood to hold the rafters in alignment
as you assemble the trusses (Photo 5). Cut a rafter
using the dimensions in Figure J and use it as a pattern
to mark the remaining rafters. Place a pair of rafters in
the jig and screw the tops together. Next screw the 2x6
crosstie and 2x8 spacer to the pair of rafters. Keep the
crosstie screws clear of the bolt hole locations. Complete
each truss by screwing another pair of rafters on top.
Check the ends and tops of the rafters as you assemble
the trusses to make sure they’re perfectly aligned. The
trusses must be identical so that your roof boards and
soffit trim will line up. Finally, elevate the truss on blocks
of wood while you drill a pair of 1/2-in. holes into each
end of the crosstie for the carriage bolts (Figure J). Run
the 1/2 x 5-1/2-in. carriage bolts through the rafters and
crosstie ends and tighten the nuts.
Frame the walls accurately
for smooth assembly
Since the wall framing for this porch is the finished surface,
it’s worth taking a little extra time to make the framing material look good. We chose the nicest cedar 2x6s we
could find and ripped them into 3-1/2-in. and 1-1/2-in.
boards. We did this to create sharp, clean edges (we also
ripped off all the factory rounded edges).
Cut the studs and crosspieces to length and screw the
walls together (Photo 6 and Figures F – H). We used a
power miter saw for clean, square cuts, but a circular saw
will work too. Use a crosspiece as a spacer when you’re
attaching the studs to the top and bottom plates (Photo
6). Then cut a 10-in. spacer block to position the crosspieces
for assembly (Photo 6, inset).
Click Image to enlarge.
6. Cut the wall
parts
according to the
plan and screw
them together.
Use the crosspieces
as spacers
to position
the posts. Screw
the crosspieces
between the
posts. Use a
spacer block to
ensure perfect
alignment
(inset).
Click Image to enlarge.
7. Stand the walls and screw the wall corners together. Align the walls flush to
the deck and screw them down. Finally plumb and brace the walls.
Click Image to enlarge.
8. Stand a truss against the house. Plumb and brace
it. Set the outside truss and screw a 1x4 brace to it.
Then stand and brace the remaining trusses. Toe-screw
all of the trusses to the top wall plate.
Click Image to enlarge.
9. Stretch a mason’s line across the peak of the
trusses to position the roof tie-in framing. Use
3/4-in.-thick spacer blocks to raise the line to the
correct tie-in framing height.
Click Image to enlarge.
10. Cut 2x8 plates and nail them to the roof.
Measure for the ridge. Cut the ridge and a pair of
rafters and nail them to the plates. The framing should
be exactly 3/4 in. above the top of the trusses.
Plumb and brace the walls
The key to standing the walls is to check and doublecheck
along the way to make sure they’re straight along
their top and bottom plates, perfectly plumb and square,
and securely braced (Photo 7).
Start by positioning the walls with their outside edge flush to the deck and screwing them down. Next screw the corners together, making sure the top plates of adjacent walls are even with each other. Use a long level to plumb the walls while you attach diagonal braces to hold them in position (Photo 7). Leave the braces in place until after the roofing is complete.
Round up a couple of strong helpers to assist in setting the trusses. Start by marking the position of the trusses on the top plate and onto a 16-ft. 1x4 (you’ll use the 1x4 to brace and position the tops of the trusses as you stand them up). The first truss simply butts to the house wall. The outermost truss aligns with the edge of the top plate, and the three interior trusses are centered on the studs below. Set the first truss against the house and carefully center it so that 1-1/2 in. of the bottom 2x6 overhangs the top wall plates on each side. Screw the truss to the top plates. Then use a straightedge and level to stand the truss perfectly plumb and brace it to the roof (Photo 8). Make sure this brace is securely screwed to the roof and the truss because the remaining trusses will be supported by this truss until the roof tie-in framing is complete.
Lift the remaining trusses onto the top of the walls and rest them on the first truss. Slowly and carefully slide the outermost truss to the outside end of the porch. Align the marks on the 1x4 with the truss at the house and the outermost truss and screw it to the trusses. Center the outermost truss on the walls and toe-screw it to the top plate of the walls. Stretch a string line between nails at the peak of the two trusses. Align the remaining trusses with the string line and the marks on the 1x4 and top plates and screw them in.
Line up the tie-in framing with the porch
for a seamless blend
One of the trickiest parts of the porch
construction is joining the two roofs.
The key is to extend lines from the new
porch and mark where they intersect
the existing roof. Do this by using a
taut string line or a long, straight
board. Remember to raise the tie-in
framing on the existing house roof 3/4
in. above the porch framing to compensate
for the difference in thickness
of the 3/4-in. plywood and 1-1/2-in.
roof boards (Photo 12).
Start the tie-in framing by locating the point where the peak intersects the existing roof (Photo 9). Then cut the 2x8 roof plates. If you’re not good at calculating roof angles, start by estimating the angles and cutting the plates an extra 6 in. long. Then set them in place, remark the angles and recut them until they fit. Screw the roof plates through the roof boards into the rafters below. Next measure for the ridge, estimate the angle and cut it a little long. Trim the angle to fit and screw the ridge rafter to the first truss and roof plates. Complete the tie-in by installing a pair of rafters (Photo 10).
Photo 11 shows installation of the roof boards. Set your table saw or circular saw to 23 degrees and rip a bevel on the groove edge of the first board. Align the board with the ends of the trusses and nail it with 16d galvanized nails. Install the remaining boards, making sure to snug the joints tight before nailing them. Let the boards hang out past the last truss to form the gable end overhang.
When you’re done installing the roof boards, snap a chalk line at the gable (outer) end and saw them off to leave an 18-in. overhang. Finish the gable end overhang by installing a pair of rafters and the 1x3 trim. Hold the gable end rafters tight to the underside of the cutoff roof boards and screw through the roof boards to hold the rafters in place. Then cut 1x3 trim to cover the end grain of the roof boards. Extend the trim around the corners and return it along the roof edge to the house.
Pay attention to flashing and roofing
details for a watertight job
Building the tie-in framing on top of the existing shingles
is a good way to keep the house waterproof as you construct
the porch, but when it comes time to install the
roofing you’ll have to cut the shingles along each of the
valleys with a hook-blade utility knife. Then pry loose the
cut shingles to make a wide path for the valley flashing
(Photos 12 and 13).
Click Image to enlarge.
11. Bevel the first roof board and nail it flush to the
end of the trusses. Nail the remaining tongueand-
groove roof boards to the trusses. Cut the last
board on each side to fit at the peak.
Click Image to enlarge.
12. Cover the tie-in framing with 3/4-in. plywood.
Add blocking as needed and fill in the triangular
areas between the existing roof and the new roof.
Click Image to enlarge.
13. Adhere ice-and-water barrier along the eaves
and up the valleys. Then nail metal valley flashing
overtop. Add No. 15 building paper, then shingles.
Click Image to enlarge.
14. Nail a 2x10 trim board over the outside joist,
1-1/2 in. below the top surface of the deck. Cut
a 2x4 sill piece to width and bevel the top on a table
saw. Miter the ends and nail the sill to the top of the
2x10 trim board.
FIGURE K Corner Details
Click Image to enlarge.
Fill in the gable ends
Cover the triangular opening in the
truss above the house wall by building
a 2x2 frame and nailing 1x6 tongueand-
groove boards to the back. Then
slide the frame into the opening and
screw it into place. Fill the triangular
space above the outside wall with a 2x4
frame (Figure C). Then staple screening
to it and cover the screens with
stops, just as you do with the walls
below. Practice on scraps to make
accurate patterns for the steep angles.
Then transfer the angles to the actual
framing members. You may have to
cut these angles with a handsaw;
they’re too steep for a miter saw unless
you build a special jig.
Install the screens
and screen door
The charcoal aluminum screening we
used is strong and long lasting, but
you have to handle it carefully to avoid
creases and dents. Carefully unroll the
screen on a large work surface and cut
lengths about 3 in. longer than you
need. Reroll each piece and carry it to
its location. Photo 15 shows how to
staple the screening to the framing.
After you stretch and staple each section,
cut off the excess screen with a
sharp utility knife. Then cover the
edges with 2x2 trim pieces (Photo
16). We screwed these on to allow for
easy removal for future screen repairs.
If you use a wood door like ours, start by trimming it just enough to fit in the opening. Then set it in place and mark the door for final fitting. Use a sharp plane or belt sander to trim the door. You may have to repeat this process a few times to get a good fit. Nail 1/2 x 2-in. wood stops to the framing at the door opening. Then hang the door using galvanized or brass screen door hinges. Mount a latch and door closer to complete the job.
Click Image to enlarge.
15. Cut lengths of screening and staple them to the
framing. Start by tacking the two corners, making
sure the screen is square to the opening. Then
stretch the screen slightly and staple the sides, top and
bottom. Place 1/4-in. staples every 3 in.
Click Image to enlarge.
16. Cut 2x2s to fit and screw them to the framing
to cover the staples along all the edges. Frame
and screen the outer gable end following Figure C.
Materials List |
||
| ITEM | QTY. | |
| 80-lb. bags of concrete mix | 10 | |
| 6x6 x 4' .60 treated posts | 5 | |
| 2x10 x 14' treated joists, blocking | 17 | |
| 5/4x6 x 14' cedar decking | 28 | |
| 2x4 x 14' cedar plates, crosspieces and gable end* | 14 | |
| 2x2 x 14' cedar screen covers* | 14 | |
| 2x4 x 8' cedar uprights* | 21 | |
| 2x2 x 8' cedar screen covers* | 21 | |
| 2x2 x 14' gable end frame | 2 | |
| 2x4 x 14' cedar (rip for sill) | 2 | |
| 2x4 x 16' cedar (rip for sill) | 1 | |
| 2x6 x 8' cedar corner boards | 4 | |
| 2x4 x 16' SPF (spruce, pine or fir) bracing | 5 | |
| 1x4 x 16' roof brace | 1 | |
| 2x8 x 12' SPF rafters | 22 | |
| 2x6 x 16' SPF crossties | 5 | |
| 2x8 x 16' SPF gussets | 1 | |
| 2x8 x 16' SPF truss blocking | 2 | |
| 2x8 x 8' SPF tie-in ridge | 1 | |
| 2x8 x 10' SPF tie-in plates | 2 | |
| 2x6 x 10' SPF tie-in rafters | 1 | |
| 1x2 x 8' SPF truss furring | 2 | |
| 2x10 x 14' SPF or cedar trim board | 2 | |
| 2x10 x 16' SPF or cedar trim board | 1 | |
| 4x8 x 3/4" CDX plywood | 2 | |
| 2x6 x 16' tongue-and-groove cedar | 46 | |
| 1x3 x 12' cedar trim | 2 | |
| 1x3 x 16' cedar trim | 2 | |
| 1x6 tongue-and-groove cedar | 48 ft. | |
| Ice and water membrane | 300 s.f. | |
| No. 15 building paper | 400 s.f. | |
| Shingles | 400 s.f. | |
| 10' lengths of metal drip edge | 5 | |
| 10' lengths of valley flashing | 3 | |
| 4' aluminum screening | 150 ft. | |
| 36" screen door | 1 | |
| Post brackets | 5 | |
| Double inverted-flange beam hangers | 2 | |
| 2x10 joist hangers | 18 | |
| Joist hanger nails | 5 lbs. | |
| 16d double-dipped galvanized nails | 5 lbs. | |
| 12d galvanized box nails | 5 lbs. | |
| 3/8" x 4" galvanized lag screws | 22 | |
| 2-5/8" deck screws | 6 lbs. | |
| 3" weather-resistant deck screws | 5 lbs. | |
| 1/2" x 5-1/2" galvanized carriage bolts, nuts and washers | 20 | |
| 1" galvanized roofing nails | 10 lbs. | |
| 5/16" staples | 1 box | |
| 2-1/2" screen door hinges | 3 | |
| Screen door closer | 1 | |
| Screen door latch | 1 | |
* Option: Rip these pieces from 2x6s. |
||
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