Installing Deck Posts for Railings

Deck railing posts must support the railing system and not break under stress.

Railing systems on decks keep people from falling off. A good railing system begins with strong railing posts installed with at least two heavy bolts. Deck railings attach to railing posts which in turn fasten to the deck joist framing. Install the deck posts before the deck boards so you have access to the deck framing. Railing construction is governed by the International Building Code and local building codes. Be sure to check with your local building department before beginning work.

Things You'll Need

• Quick clamps
• Post level
• Cedar shims
• Drill
• 1/2-inch drill bit
• 6-inch long, 1/2 inch carriage bolts
• Hammer
• 1/2-inch washers and nuts
• 3/4-inch socket
• Ratchet

Instructions

1. Position a deck railing post inside the deck framing at a deck corner. Clamp the post to the deck joists on both sides of the corner. The bottom of the post should be flush with the bottom of the deck joists.

2. Place the post level against the top of the post and adjust the post to center both bubbles on the level's vials. Ensure the post stays flush with the bottom of the joists. Use shims to fill any gaps between the post and the joists. Use the elastic strap on the level to keep it in place.

3. Mark the bolt placement on the joists. Mark two locations on the front of the deck. Make the first mark 1-inch from the joist bottom and 1-inch from the right side of the post. Make the second mark 1-inch from the joist top and 1-inch from the left side of the post. Mark a third bolt location on the side of the deck in the center of the joist and the center of the post.

4. Drill three 1/2-inch holes through the deck joists and the post at the marks just made. Insert 1/2-inch carriage bolts through the joist and through the post so the bold head is on the outside face of the deck. The fit will be tight and you will probably need to use the hammer to tap the bolt through the hole.

5. Place a washer on each carriage bolt, followed by a nut. Hand tighten the nuts as far as possible. Use the socket and ratchet to tighten the nuts firmly--tight enough that the carriage bolt head should pull into the wood slightly and dimple the wood surface but not break the wood fibers.

6. Add additional posts between the corner posts as required by local code or the deck design. Install railing posts no more than 8-feet apart in most cases and 6-feet is better. Center posts only need two bolts, but any time post placement allows a third bolt to be used, use it for the additional strength to the railing system it will add.

Tips & Warnings

• Drill through the joist, into and through the post, not from the post into the joist.

• Joists 2-by-8 in size or larger will have enough room for two bolts on both sides of the corner. Make the holes 1-3/4 inches from the top and bottom of the joist and 1-inch from the left and right of the post.

• If you plan to install trim pieces around the face of the deck, countersink the bolt holes 1/4-inch with a 1-inch spade bit.

• Wear safety glasses while using the drill and tapping the bolt with the hammer.

• The fit of the bolts should be tight. Don't ream the holes out to make insertion easier.

References

• "Decks 1-2-3"; The Home Depot; 2002

Resources

• Decks: Deck Rail Post Attachment