Online Math Whiz
While designing this project, we discovered a smart (and free!) Web site that does complicated roofing calculations for you. Go to www.blocklayer.com and input your structure’s dimensions and the type of roof you’d like to build. The site produces the precise angles, cuts, spacing and other details for all hip, rafter and creeper boards — no more head scratching or wasting time and materials because of mathematical mistakes. (Keep in mind, however, that due to factors such as variations in lumber dimensions, etc., you’ll most likely have to make slight adjustments as you assemble the roof.)
Prep the Foundation
To allow for proper drainage and prevent grass and weeds from growing beneath the gazebo, first mark the 12 x 12-ft. pad; then remove the sod and about 3 in. of dirt within the marks. Add a layer of landscape fabric and top it with approximately 3 in. of class II gravel (photo 1).
Cover the foundation with landscape fabric and about 3 in. of class II gravel to prevent weed growth.
Next, dig four 12- to 14-in.-dia. holes (one in each corner) to accommodate the 8-in.-dia. Sonotube forms for the concrete footings. Dig at least 24 in. deep or to the frost-line depth for your area.
Mix the concrete and start by filling the holes half full. Insert the Sonotube forms so that the distance from the center of one footing to the center of the adjacent footings measures 10-1/2 in. and the diagonal distance between the centers of the footings is 14-4/5-in. Use a laser level (photo 2) to make sure the tops of each form are at an even height. (The yard where we built this gazebo was slightly sloped, so the footing elevation above each hole varied.)
Dig four holes for the footings and partially fill them with concrete. Place the Sonotube forms in the holes and check that the centers are square. Use a laser level to ensure equal height across the tops of all Sonotube forms.
Finish filling each hole and form with concrete and smooth the surface; then insert a mudsill anchor in the center of each footing. HANDY’s contractor for this project, Mike Conner, borrowed the idea of employing mudsill anchors from a friend who has great success using them to build decks.
Once the concrete has cured (usually after 24 to 48 hours), use a reciprocating saw or sharp utility knife to remove the Sonotube form from the outside of each footing (photo 3).
Fill the holes and Sonotube forms completely with concrete and insert a mudsill anchor into each footing. When the concrete is dry, cut away the Sonotube forms.
Build a Simple Deck
Create the deck frame by cutting two 2x10 boards to 10 ft. 9 in. Double-check that the pieces rest level on the concrete footings. Cut two more 2x10 boards to 10 ft. 6 in.; they will fi t between the longer boards to create a square frame. Fasten the pieces together and box the frame (photo 4). Add shims where there are spaces between the boards and the concrete footings. Secure the frame to the concrete footings by wrapping the mudsill anchors around each board and nailing them in place with joist-hanger fasteners (photo 5). Be sure to keep the box straight and level while attaching the straps.
Build the deck frame on the concrete footings, making sure that the mudsill anchors are prepped to wrap around the boards. Then ensure that the frame is square.
Secure the mudsill anchors to the deck frame. A palm nailer works well for building the deck portion of this project.
Next, cut 10 4x4 posts to 6 ft. 8 in. Using 4x4 joist hangers, fasten one post inside each corner of the deck frame and the rest of the posts along the sides (photos 6 and 7). Drive a ledger board fastener through the frame and into each post.
Use nails to attach the 4x4 joist hangers inside the deck frame.
Insert 4x4 posts into the hangers and screw ledger-board fasteners through the deck boards and into the posts.
Mark the locations of the 2x10 joists 16 in. OC (or 15-1/4 in. from the end of each previous joist); then cut all joists to fit within the frame. Be sure that the crown of each board faces up. Conner recommends nailing the joists to the frame to hold them in place while attaching the 2x8 joist hangers (photo 8). Secure each 2x8 joist hanger to the frame using joist-hanger fasteners. (Be sure to drive a nail in every hole.) If you run into a space where there isn’t enough room for a hanger (as we did), use shims and locking screws to attach the joist to the frame (photo 9).
Check that the crown of each 2x10 joist faces up. Nail the joists in place first; then add the joist hangers.
For spaces where there isn’t enough room for a joist hanger, use shims and locking screws to attach the joist to the frame.
Attach two 2x6 boards (decking blocks) to the ends of the deck frame that run parallel to the joists (photo 10). This will provide a sturdy surface for nailing the deck boards in place.
Add a double-layer of 2x6s (decking blocks) inside the deck frame at the ends that run parallel to the joists.
Add the deck boards next. To create a finished look for the perimeter of the deck, let the edge pieces overhang slightly and miter the corners. You’ll have to notch the edge pieces and the adjacent deck boards with a jigsaw to fit around the 4x4 posts (photo 11). Top the rest of the frame with deck boards cut to fit within the edging. To find the right spacing, lay out all of the boards before fastening them. Using a hidden-fastener jig such as the Camo Marksman, secure the boards to the frame, creating a smooth surface (photo 12).
Notch and miter the decking trim boards and secure them in place along the edge of the frame.
Use a hidden-fastener jig such as the Camo Marksman to attach the decking to the joists.
Construct the Rafters
Begin by measuring and cutting eight 2x4s for the top plate. Secure two stacked boards on top of the 4x4 posts along each side of the gazebo; then add 2x4 support brackets to each corner (photo 13). Next, refer to the rafter layout (in PDF, below) to cut the rafters and hips one at a time as you assemble the roof. This will allow you to make slight adjustments as necessary.
Attach the top plate to the 4x4 posts and add support brackets to the corners of the gazebo.
Start by creating the four common rafters (to be installed from the center of each side of the top plate to the center point of the roof). Cut four 8-ft. 2x6s to 7 ft. 6-3/4 in. Mark and cut the angles for the setbacks and bird’s-mouths to achieve the proper height above plate (photo 14A and 14B). Cut the overhanging ends to achieve the desired length and finished edge. Attach the common rafters to a ridge, a 6-in.-long x 1-1/2 x 1-1/2-in. piece at the center point of the roof.
Cut two common rafter boards and attach them to the ridge. Fit them in place along the top plate, making sure that they are at the correct height above plate (HAP). Mark and cut the bird’s-mouths (14B) for both boards.
Next, measure, mark and cut four 2x6 hip boards (to be installed from each corner of the top plate to the center point of the roof) one at a time to make sure you achieve the correct length, setback and bird’s-mouth. Each hip will have a compound miter on one end for securing to the adjacent main rafters and ridge (photos 15 and 16). Cut the overhanging ends to the same length as the common rafter boards. To ensure accuracy and to speed up the process of marking and cutting the overhanging ends of all subsequent boards, Conner suggests adding a nail to the end of each hip board (one in each corner) and tying a string across all sides.
Install the hip boards, making sure to cut the correct compound miters that will attach to the ridge and adjacent common rafters.
Making sure to mark the correct spacing, setback, bird’s-mouth and end cuts for each, continue adding three boards (creepers) to each side of the four hip boards (photo 17). There will be eight creepers of each length.
Attach three creepers to each side of the hip boards; use nails and string to mark the end cuts for all boards.
To make the roof panels, we laminated 3/4-in. water-resistant plywood (for the top face of the roof) and 1/4-in. non-water-resistant plywood with a high-grade veneer (for the underside). Creating this double layer prevents the roofing nails from puncturing the ceiling of the gazebo.
Use construction adhesive to glue each 4x8 sheet of 1/4-in. plywood to a sheet of 3/4-in. plywood to create eight panels. Once the adhesive has cured according to the manufacturer’s instructions, lift the first panel onto the bottom edge of the roof framing and screw it in place along the common rafter. Snap a chalk line to mark the cut location along the hip; then use a circular saw with the depth guide set to 1 in. to make the cut (photo 18). Use the scrap pieces for the upper portions of the roof. Repeat these steps until the roof is completely covered with plywood.
Enlist a couple of helpers to lift the plywood panels onto the roof framing. Use a circular saw with the depth guide set to 1 in. to make cuts.
Though this is an open-air structure, adding a vent will help to allow air and heat to escape, preventing too much uplift under the roof. After you’ve installed the vent, add the drip edge to the roof using a hammer and nails (photo 19); then cover the plywood with a layer of roofing felt and staple it in place. Top the felt with an armor of shingles (photo 20).
Install the drip edge; use tin snips to cut the corner.
Cover the plywood with roofing felt and shingles.
Install the Railing and Apply Finish
We chose to use Deckorators 26-in. classic-baluster railing from a local home center for this project. To install the railing, start by attaching the top and bottom metal rails to the top and bottom 2x4s for each section of railing. Then screw all plugs in place and insert the balusters.
Next, mark the cut locations for the top and bottom 2x4s for each section and cut them to size (photo 21). Install each section of railing by screwing it in place between the 4x4 posts. Tip: Use a couple of pieces of scrap 4x4 to prop up each railing section from the deck; this will ensure that all sections are installed at the same height (photo 22).
After assembling the sections of railing, fit them in place and mark the cuts.
Use scrap pieces of 4x4 to prop up the railing; secure it in place.
Once the railing was installed, we sprayed on a cedar-color semitransparent water-base stain from Thompson’s WaterSeal. You can apply the finish of your choice. After the stain dries, all that’s left is to furnish your gazebo with a couple of chairs and perhaps a small table or two; then you’re ready to relax and enjoy the fruits of your labor.