Installing Beams

Installing the Beams

Form and pour the footings with J-bolts and allow the concrete to cure for 48 hours. Install post anchors and install posts that are a foot or so taller than they need to be. Plumb the posts using a post level and brace them firmly with 1x4s so they won't move when they get jostled during beam construction.

Building a two-part beam
Some inspectors prefer an on-top beam made of two 2xs fastened together because the resulting beam is actually stronger than the sum of the two parts. Others prefer the two-part beam shown on these pages because attaching to the sides of the posts adds stability. Most inspectors will accept either type of beam. Confirm local requirements.

Prestart Checklist

Time
With a helper, about six hours to measure and cut posts, build two beams, and install the beams

Tools
Tape measure, post level, carpenter's level, hammer, drill, bit for installing carriage bolts, circular saw, mason's line, handsaw, clamp, layout square, adjustable wrench or socket and ratchet

Skills
Measuring and cutting, checking for level and plumb

Prep
Install and anchor the posts

Materials
Lumber for beams, 16d galvanized nails or 3-inch deck screws, 7-inch carriage bolts with washers and nuts

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Beam and Ledger Overview

Four piers sunk into the yard support the beam for the upper level, while two piers cut into the slab support the beam for the lower level.

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Step 1

Check that the ledger is straight using a mason's line and two 1x2 blocks. If it has waves of 1/2 inch or less, install the outside joists and header first, then add the inside joists. If the ledger has major waves and you install the header now, you will have to measure joists individually.

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Step 2

Rest one end of a straight board on the ledger and have a helper check for level as you mark a corner post. From this mark, measure down the width of the joists to mark the top of the beam. Repeat for the other corner post.

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Step 3

Measure down the width of the beam stock and attach a temporary brace to each corner post to support the beam pieces as you work.

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Step 4

Cut two beam pieces to length and mark them for post locations. Put a beam piece on the temporary brace with its crown side up and adjust it until it is level. Temporarily fasten it at the end opposite the brace with a 3-inch screw. Install the second member on the other side of the post. Double-check that the beam is at the correct height to support the joists.

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Step 5

Clamp the beam members tightly against the posts. Attach the second piece in the same way as the first. Counterbore the inside face of the beam if you want to recess the bolt nuts. Using an extended drill bit, drill two holes for the carriage bolts through the beam members and the post.

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Step 6

Tap 7-inch carriage bolts through the holes. Make sure the bolt heads face the outside of the deck; they look more finished than the nuts.

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Step 7

Slip a washer and turn a nut onto each bolt. Tighten the nut with a ratchet wrench. It's a good idea to use a deep socket or an extension on the wrench to avoid banging your knuckles on the beam.

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