Construction Common and Deck Common are excellent economical redwood grades for this project. They are easy to work with and accept a variety of finishes. Where increased decay resistance is needed, use all-heartwood grades: Construction Heart or Deck Heart.

This project requires careful planning and measuring during construction of each of its main components: layout, posts and footings, decking, frieze, rafters and roofing, and railings.

If you are a relative newcomer to do-it-yourself projects, follow the construction steps presented here and seek help whenever you are unsure of the details. More experienced d-i-yers will feel comfortable with this basic design and will find several areas to add personal touches. A few ideas for frieze, railing and roofing options are offered.

Use only corrosion-resistant hardware. Check local building codes before planning construction.

If you think of an octagon as a square with its corners cut off, you'll realize how simple the shape truly is. A common measurement and trim angle to remember is 22-1/2 degrees. The key, as with any project, is both careful planning and precise measurement.

At a level building site, use batter boards and string to lay out a square twelve feet on each side. To check for 90-degree corners and to find the center of the gazebo, run strings from corner to opposite corner. The square is true and its sides are parallel when the diagonal measurements are equal.

Where the two diagonal strings cross, drive a stake into the ground to mark the position of the center footing. 

Once squared, make a mark along each string 42 inches from the corner in both directions. Use a plumb bob and chalk to transfer each mark from the string to the ground, and drive a stake to mark the center of each post position. The measurement from post center to post center should be 60 inches.

Snap chalk lines from post stake to post stake to create the gazebo outline on the ground. Remove the string from one side of the layout at a time while you dig the holes for the concrete footings. Do not remove the batter boards yet, as you will need to restring the gazebo layout later to help set the post anchor bolts.

The footing holes should average 12 inches in diameter, be at least 3 feet deep and be larger at the bottom than at the opening. Fill the base of the hole with several inches of compacted gravel. In cold climates, footings should extend 6 inches below the frost line or comply with local codes.

Make 12- by 12-inch square wood frames from 2x4 lumber for each footing to contain the concrete at ground level. Restring the gazebo layout now so that the frames can be centered for positioning the anchor bolts and posts later. Level the frames to each other and use backfill or stakes to secure the frames while pouring the concrete.

Post Anchors

Use adjustable post anchors and quick-setting concrete. Pour the center footing first and set a 6-inch long 6x6 wooden nailing block at a depth of several inches into its center so that at least four inches remain above the concrete. Trim this block to height later when framing in the deck.

Pour perimeter footings and set anchor bolts one at a time. All anchor bolts should measure six feet from the center of the gazebo and five feet from each other. Check each for plumb and level. This is important for the gazebo to properly fit together. Make any adjustments before the concrete sets completely--about 1/2 hour.

Once the concrete is set, assemble the post anchors square to the center footing and with the required 22-1/2 degree angle between posts. Remove the 2x frames.

The decay-resistant redwood grades, Construction Heart or Deck Heart, are ideal choices for the posts. Cut a notch 6-3/16 inches deep and 1-1/2 inches wide in the tops end of each 4x4 post for attaching the roof rafters. Trim the 4x4 posts to 9 feet 5 inches.

Cut a double bevel of 22-1/2 degrees beginning 5-1/2 inches from the bottom. Attach posts to footings at each metal post anchor with 10d nails. Offset the posts toward the center of the gazebo and make sure the beveled edges clear the sides of the post anchor so that the rim joists can be attached later. Plumb and brace posts.

Deck Understructure

The deck framing is constructed near the ground, so use Construction Heart or Deck Heart grade redwood. Use corrosion-resistant deck screws, nails and metal joist hangers.

Deck Joists   Measure and trim a single 2x6 redwood joist to span the width of the gazebo between opposite posts. Use a string level to guide you in attaching the metal joist hangers to the posts with 10d nails. Trim the center nailing block to height so that the spanning joist will sit on it. Secure the spanning joist to the post and toenail it to the center nailing block.

Headers   Trim ends of 2x6 headers to opposite 22-1/2 degree angles. Use 16d nails to attach the headers to the deck joists where the joist span become greater than 24 inches and where a whole deckboard will cover them.

Rim Joists Trim 2x6 redwood rim joists with 22-1/2 degree opposite angles. Attach rim joists to the outside of the beveled posts with two four-inch, self-tapping screws per joint. Measure and trim the remaining eight intermediate joists to run from rim joists to headers. Attach with joist hangers.

Decking  

Install 2x6 deck boards with two deck screws or 16d nails per bearing. If you use nails, pre-drill holes at board ends to prevent splitting. Choose Construction Common or Deck Common redwood, grades with pleasing blends of heartwood and sapwood, for a long-lasting and economical deck.

Start the decking installation at the rim joist and notch the first row of deck boards to fit around the posts. The deck boards should trim to 22-1/2 degrees at their ends to butt join at the centers of the deck joists.

To ensure accurate trims and spacing, lay out the first section of deck boards without trimming or nailing them. Snap chalk lines across the boards along the centers of the deck joists to mark the end cuts and nailing patterns. Use a 16d nail to space the boards. Nail heads should be flush with the board surface.

The frieze is a decorative element which can be constructed to match the railing design or a design element of the home. Since this frieze also supports some of the weight of the roof, it is constructed with a combination head and top rail.

Lattice  

Read-made 3/8-inch redwood lattice panels are trimmed to 12 inches wide by length needed--about 56 inches.

Rails  

Use pre-manufactured dadoed 2x4s for the top and bottom rails. Trim all rails to length with opposite 22-1/2 degree angles where they attach to the 4x4 posts. Measure each post-to-post section separately, measuring from the outside edges to ensure a snug fit. Drill 3/8-inch drain holes in the bottom rails every 8 inches to prevent water damage.

Secure the head rail to the top rail with four 2-1/2 inch screws driven from the top rail into the head rail on both sides of the dado. Insert the lattice panel into the top and bottom rail dadoes and secure with 8d finish nails.

Assemble the frieze sections on level ground, and against a straight edge to keep them square, before toenailing them to the 4x4 posts. Complete the frieze with four trimmed-to-fit 1x3 redwood boards toenailed to the rails with finish nails.

The sixteen 2x6 redwood rafters join a 7-inch long octagonal 6x6 kingpost at the peak of the gazebo roof.

Kingpost  

Cut the kingpost using a table saw, or buy a ready-made one. The eight main rafters trim to about 98 inches long with 26-1/2 degree parallel cuts.

Rafters  

Attach two rafters to opposite sides of the king-post. Center this assembly atop the gazebo with the rafters running ends set into the post notches. Drill pilot holes through both the rafters and the posts. Secure with 4-inch bolts.

The eight intermediate rafters trim to length after installation. Cheek cut and nest them between the main rafters at the king-post. Toenail the running ends to the head rail.

Remove bracing from the posts.

A variety of roofing options are available and three styles are discussed here. Redwood slat roofs are economical, easy to install and offer varying degrees of protection from the sun. Wood shingles can be installed over a paper and plywood base or can be nailed directly to spaced slat sheathing which is constructed similarly to the slat roof. Shingled roofs offer full protection from the sun and rain.

Redwood Slat Roof  

Slat size, spacing and angle determine the amount of light and sun exposure inside the gazebo. For the fairly exposed design shown here, use one of the 1x4 redwood slats for 3-1/2-inch spacing. Pre-measure and carefully mark the rafters with slat positions for faster and easier installation. Snap chalklines down the center of the rafters to guide the 22-1/2 degree slat-end trims. Nail the slats directly to the rafters using two 8d nails per bearing. Predrill holes at slat ends to prevent splitting.

Shingles Over Spaced Sheathing  

Follow the basic slat roof construction steps. Add two more slats at the roof's edge to simplify installation of the starter course. Space the rest of the slats five inches on center or to match the weather exposure. Other installation details are the same as for shingles installed over plywood sheathing.

Shingles Over Plywood Sheathing  

Each two-piece section of sheathing is cut from one 4x8 sheet of plywood. Use 8d nails to install the roof panels, allowing 1/8-inch expansion gaps at the joints. Attach metal drip caps at the eaves. 

Lay and staple 36-inch wide roofing paper in layers as shown. Begin installation with the starter course made up of a double row of shingles overhanging the sheathing by 1/2 inch. Snap chalklines to ensure that additional courses are installed in straight lines. Weather exposure should be slightly less than one third the total length of the shingle. Stagger the gaps at least 1-1/2 inches and leave 1/8- to 1/4-inch spaces between shingles.

Nail shingles with two roofing nails approximately 3/4 inch from each edge and 1-1/2 inches above the butt line of the next course. Nails must penetrate at least 1/2 inch into the sheathing. Use longer nails on the ridge caps to penetrate the sheathing.

Ridge caps are available ready-made for easier installation or make your own. They should be trimmed to 4-5 inches wide with a 35-degree bevel on one edge. Install with alternate overlaps and with two nails on each side 6 to 7 inches above the butt edge. Finish at the peak with shingles trimmed to about 8 inches from the tail end.

Finial  

To prevent water damage to the kingpost and rafter joint, attach metal flashing to the roof peak before toenailing the finial to the kingpost. Caulk the joining edges and any exposed nail heads.

Custom railings and fills give a gazebo a distinct design personality because, next to the roof, they can be the most visible element. Wood railings and fills come in a few basic styles with almost limitless variation. From solid slat to cutout, from squared baluster to turned, choose a style that enhances the overall gazebo design. Follow the basic construction steps for solid slat railings or choose to use 1x1 nailing cleats as shown in the illustration.

Solid Slat Railings  

Use ready-made dadoed redwood 2x4 rails to make railing construction easier. Nailing cleats can also be used to secure slats. Railing height from the deck surface should be 36 to 40 inches or conform to local building code.

Take the outside post-to-post measurements, and trim railing ends to 22-1/2 degrees or match the post angles. Drill 3/8-inch diameter drain holes every 8 inches in the bottom dadoed rails. Cut the 1x8 redwood railing slats to at least 32 inches. Use 10d nails or 3-inch screws to attach bottom rails to the posts 4 inches above the decking. Insert the slats and cap with the 2x4 top rail secured to post with 10d nails or 3-inch screws.

Cut Out Slats  

This style often expands on a custom design detail from the frieze and it can be as simple as the oval pattern shown or as elaborate as the gingerbread designs of the Victorian era. Create a template from hardboard and transfer the pattern to the 1x8 redwood slats. Use a band or saber saw to cut the pattern from several boards at a time. Secure the redwood slats to the rails with nailing cleats.

Balusters  

Squared or turned baluster railings open up a gazebo to its surroundings, while giving it both a traditional and elegant look. Ready-made, turned 2x2 balusters cost just a bit more than the squared balusters and some suppliers also offer matching posts. With the proper tools, you can create your own custom balusters of simple or ornate design. Use dadoed rails or nailing cleats to secure the balusters, and space balusters no more than 4 inches apart for safety.

You can also assemble baluster-style railings without using nailing cleats or dadoed rails. Drive 8d nails up through the bottom 2x4 rails into the baluster bottoms, and then carefully toenail the top of the baluster to the top rail, hiding the nail heads.

Nailing Options  

The details show two options for constructing slat or baluster railings with 1x1 molding used as nailing cleats.

Sanding and Finishes  

Sand railings with medium grit sandpaper. Apply a water repellent finish.