Tips for attaching and bracing rafters, as well as lifting heavy beams when building a patio overhead.

By Don Vandervort, HomeTips

When building a patio roof, gazebo, or other outdoor shelter, it can be trickly to build the post-and-beam structures that support the rafters. Here are some tips for how to do this:

Attaching Rafters to Beams

There are various ways of attaching rafters to a beam. The most common method of fastening them to the top of a beam is to drive in screws at an angle.

When doing this, it may be necessary to drill pilot holes first so the wood doesn’t split. If the rafters will slope, use seismic anchors (also known as rafter ties), as shown above.

Although one standard anchor is adequate in most cases, a second one may be required diagonally across from the first one in high-wind or seismic areas; consult your building department for local standards. With conventional anchors, you must notch the rafters to fit or use a double-sided anchor to avoid notching.

Bracing Rafters

Where rafters span long distances or are spaced wide apart, they are prone to twist or buckle unless braced with blocking. The width of the rafters is also a consideration; those made from 2 by 8s or larger lumber require more blocking than those made from 2 by 6s.

Spacing between blocking is typically determined by local codes. If rafter spans are less than 8 feet, headers (perpendicular rafters) nailed across the rafter ends are adequate for rafters that sit on top of beams.

Snap a chalk line across the rafters where the blocking will go, and then work your way across the joists, measuring and notating the lengths of blocking you’ll need.

The easiest method of placing the blocks is to stagger them from one side of the chalk line to the other, as shown at left. By using this technique, you’ll be able to face-nail the blocks instead of toenailing them. Use 16d nails.

For a decorative accent and to hide metal post caps, you can cut and miter trim stock to fit around the post tops.

Lifting & Seating Heavy Beams

Hoisting a large beam atop a post over your head demands considerable strength; always get help for this stage of construction.

After cutting the beam to the proper length, drag it into position next to the posts and slip a short length of 4 by 4 under one end. With a helper, raise that end of the beam and maneuver it into the post cap.

Partially drive in one nail to secure the beam before you lift the other end. Raise the other end using the same technique. Then finish fastening the beam to the post caps.

Though metal post-and-beam connectors are strong and easy to use, you can secure this connection using other methods. For example, you can nail a pair of wooden cleats to each post’s top. (See How to Install Patio Roof Rafters for examples of both.)

Or, for a design that utilizes paired 2-bys to provide the support a single beam would otherwise afford, you can mount pressure-treated plywood cleats to the underside of the pair and screw them to the post tops.

Patio Roofs & Gazebos
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