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Attached Pergola

Most decks are long on sun and short on shade. Many jut out from the house with little to ease the transition between indoor and outdoor spaces. This pergola design creates an ideal blend of shade and light. Building the pergola where the deck meets the house on two sides creates a cool retreat, and it provides welcome relief from the harsh morning sunlight coming through the east-facing master bedroom window.

We built the pergola out of cedar to match the deck railing. The simple construction required only a portable circular saw, router, jig saw, a drill, and a few hand tools. A table saw makes ripping the slats easier, but isn’t essential.

Pergola Made for the Shade

Structurally, our pergola connects to the house and the deck, but your deck or back yard may present a situation better served by a freestanding structure. You can adapt our project’s post and beam construction to support both ends of the rafters, excavating post holes or using footings and deck hardware to hold the posts in place. We gave the rafter tails a simple curved shape that matches the deck railing design.

Laying Things Out

Most add-on construction starts by attaching an over-long ledger board to the house, then working out from there. This time, however, I altered the routine a little. While I did begin by laying out the ledger’s position, I didn’t attach the ledger until later. I found that by installing the beams first, and spacing the rafter positions along them, I could easily determine the correct length for the ledger. In addition, this allowed me to cut the ledger safely on the ground. Unwittingly, I also realized another benefit: I could drive the ledger mounting screws in areas that would be covered by the rafters -- a detail that enhances the pergola’s overall craftsmanship.

To figure out how long the outer post needs to be, measure from the beam mark on the fascia to the deck surface. Then add to this number the width of the skirt board (9-1/2" in my case) plus an extra foot to allow plenty to spare for trimming. Cut your post to length, then layout a half-lap so it fits the skirt board (1-1/2'' deep x 9 -1/2" long in my case). Cutting a half-lap for the pergola post is easy with a circular saw and a chisel.For my post I also cut dadoes to support the deck railing. Since cedar sawdust can irritate your lungs and skin, I suggest that you wear a dust mask and do all the machining outside. Here’s another tip: Brush an outdoor oil finish onto your post now, and do this to each piece before it’s installed. It’s much easier and more thorough to do it before the pieces are assembled.

Position your post on the skirt board, check it for plumb, then drill holes and bolt the assembly together. Next, transfer the beam mark from the fascia to the post. If your level won’t span the distance, use along, straight-edged board with your level placed on it. Scribing a post to fit against lap siding may seem over-the-top, but the end result gives you a no-gap, custom look. And it’s relatively easy to accomplish with just a circular saw, a handsaw and a chisel. Cut the post to length to fit snugly between the deck and the house’s soffit. Set the post against the siding, and use a compass to trace the siding profile onto the post. Next, following the scribed outline, use a square to draw lines indicating the bottom edge of each piece of siding. Be sure to draw the lines on the surface of the post that will face the house. Make a saw cut at each line.

Beam Mounting Details - Install the Inner Post

I considered using metal joist hangers to support the ends of the beams where they connect to the house, but decided that for appearance sake, the beams need a post here to match the outer ends. Rather than let this inner post rest only on the deck, I wanted it fastened to the wall to keep the beam from shifting away from the house. For clean fit, I scribed the post to the siding. After scribing the post for the siding I held it in position and drilled counterbored pilot holes for some beefy toggle bolts. Tightening the bolts in the anchors really snugged the post to the house. Next, I transferred the location of the beams’ top edges from the fascia board to this post like I did earlier on the outer post.

Mount the Beams

I began preparing the beams for their installation by scribing one end of each piece to fit against the siding. Going into this project, I was concerned about mounting the beams to the posts, because it involves hoisting two long, heavy boards. By carefully laying out the mounting bolt holes in both the posts and beams, and allowing for minor adjustments, I was able to minimize the amount of lifting.

Lay out the mounting bolt hole. Then measure the distance from the center of the inner post to the center of the outer post. Use this distance to layout the mounting bolt holes on the outer end of the beams. Complete this step by drilling the 1/2"-diameter holes. Next, lay out and drill the holes in the posts for the bolts.Using a 5/8"-dia. bit allows enough play for installing the bolts. Attaching the beams one at a time made the assembly process much more manageable. To do this, I inserted a bolt through the lower hole at the outer end of one beam, raised the beam into position and slid the bolt through the outer post. Then I slipped the other beam onto the bolt, and spun on a washer and nut. I repeated the process at the innermost. Finish up this phase of the project by cutting the tops of the posts flush with the tops of the beams. I used hand saw, letting the blade rest on the beams as I made the cut.

Ready for the Rafter

At this point, the pergola still didn’t look like much, but the rafters soon changed that. Before I could shape the tails, I needed to cut the rafters to length. Rather than cut them all to finished length, I left them 1" long so I could custom fit each one to accommodate minor variations in distance between the house and the pergola beam assembly. (Any discrepancies here could get amplified when the gridwork of slats goes on.) Since the outermost rafter gets nailed to the end of the ledger instead of its face, I cut it 1/2" longer than the rest. As I mentioned earlier, each rafter has a pair of notches that fit over the two beams (Rafter Pattern). To make sure these notches align perfectly from rafter to rafter, I gang-cut them with procedure similar to throne I used to cut the halflap in the outer post. I aligned the tail ends of the rafters and clamped them together, then marked the location of the notches.

Next, I used framing square for accuracy to guide my circular saw while cutting one edge of a notch layout. With my saw blade set tout 1/2" deep, I made this pass, then I shifted the square over tout the other side of the notch. Following the wood plans , I then made several passes between the first two and cleared the waste with chisel. Repeating this sequence for the second notch completed the step. Duplicating the elliptical tail shape on 16 rafters presented a greater challenge, but I simplified things busing a template and a flush- trim router bit. First, I laid out the ellipse on apiece of oversized 1/2" plywood (Rafter Pattern). I cut this pattern roughly to shape, then used sanding drum in my drill press to sand the template to final shape. Next, I screwed a fence on each side of the template to align the profile automatically on each rafter. Using the template, I marked the tail profile on the rafters, then cut the tails to shape with a jig saw, staying about 1/8" outside the line. Then I clamped the template to each rafter and routed the tail to final shape. Routing a chamfer on the exposed edges of the rafters wrapped up the machining.

Installing the Rafters

Starting at the inner post, I marked centerline for each rafter every 12" along the top of the beam assembly. Once I had the outermost rafter location marked, I measured the distance between the fascia and the beam assembly, and trimmed this rafter to length. Next, using a framing square to position the rafter, I toe nailed it tithe fascia, first from the bottom toehold it in place, then from each side. Pre-drilling pays dividends here, before toenailing the rafter to the beams. With this rafter installed I measured for the ledger board’s exact length. Once it was cut, a neighbor held one end of the attached pergola ledger in position while I screwed the other end tithe fascia. I placed the remaining screws so they would be covered by the rafters. When I got ready to install the next rafter, I happened to sight down the beam assembly and found that it bowed toward the house slightly. A stringline stretched between the outermost rafter and the inner post confirmed my eyeball appraisal. Remedying the situation called for installing every third rafter, carefully fitting and trimming them to lengths they pushed the beams into alignment with the string line. Each rafter was toe nailed to the ledger. Installing the remaining rafters moved along quickly.

Predrilling Ensures Success

Toenailing, especially in brittle wood like cedar, can cause your stock to split. But you can minimize splitting by drilling pilot holes. For our 10d galvanized casement nails, we drilled 3/16" pilot holes at an angle.

Adding the Slats

As tempting as it sounded to setback on the deck and enjoy my progress so far, I decided to keep plugging away to wrap up the project. Besides, the slats are what really create the shade. Trying to find a piece of lumber 18 ft. long is like searching for the Holy Grail, so I ripped 10-ft. long pieces from relatively clear 2x10 lumber. I tried to rip these as straight as possible, but still planned on dealing with some warping and twisting. First, I trued one edge of each 2x10 by snapping a chalk line and shaving to the line with a hand plane. Using this edge as a guide, I ripped the slats using my circular saw equipped with an edge guide. Then I chamfered the edges of the slats as I’d done previously on the rafters, posts, and the beams. The slats won’t span the pergola’s entire length, but to make the them appear continuous from below, place all butting ends directly over a rafter. Begin installing the slats by measuring out 6-3/4" from the ledger at the first and last rafters, then snap a chalk line between these points.(Even though the slats are 6" on center, this extra 3/4" on the initial measurement allows you to align the edge of the slat with the mark instead of trying to position it blindly over centerline.)

Mark the remaining slat found it best to install the slat nearest the ledger first, then work my way outward. The 6x12 grid openings make for close quarters. Staying to the open side gave me plenty of elbow room to drive the screws. Start at the outer end of each slat, and work your way way toward the house. Be sure to adjust the slat’s alignment at each rafter. Two drained cordless drill battery packs and 187 screws later, I was done and ready to trade misstep ladder for a deck chair. As I lay back, I tried to decide what kinds of plants and vines would add to the pergola’s beauty, and in time provide even more shade. That phase of the project will only grow better with time. This classic cloud-lift design is based loosely on Craftsman-style construction typical of bungalows.