Wood Deck Railings - Posts
How to install posts for wood deck railings. There are several methods of installing posts for wood deck railings.
Wood deck railing posts will fall into the following categories:
Exterior Mounted Posts
The first and most obvious way to install wood railing posts on a deck is to attach them to the outside face of the rim joist.
First determine the spacing between posts, never more than 8' and usually between 4' and 6'. Cut the posts to length. The total length includes the overlap on the rim joist, the building code minimum railing height and any extra for a protruding post cap (if desired).
For a deck 30" (24" in Canada) to 5'10" above ground wood deck railings must be at least 36" so the total post length would be 42" to 48".
For a deck 5'10" or more above ground wood deck railings must be at least 42" so the total post length would be 48" to 54".
Use a 4x4 post and cut a 1.5" x 6" notch out of one side of the post.
To stiffen the rim joist where the post will attach, insert another piece of 2x8 or 2x6 behind the rim joist and between joists. Or attach another rim joist to the outside of the deck frame.
Either of these options will stiffen the outer edge of the deck where the post will attach.
Predrill between 2 and 4 holes (1/4") through the front face of the post and the notch. Set the post into position on the rim joist and using the holes as guides, drill through the rim joist.
To secure the post in place, position the notched post on the rim joist and check for level. Use cedar shims between the notch and the rim joist as required to achieve level from the front and side views of the post.
Interior Mounted Posts
Follow the same procedure as for exterior mounted posts but this time, position the post against the inside edge of the rim joist. Use shims between the joist and the post to ensure level is attained. Screw the post against the joist.
Unfortunately designs for wood deck railings with posts notched and secured in or against the deck framing remain vulnerable to water damage. They will all eventually rot at the juncture of the post and deck.
However, there are a couple of things you can to do so slow rotting of posts on wood deck railings. Promote water flow away from posts and use surface mounted post achors.
Allow Water to Flow Away From Posts
To promote water flow and reduce rot between the contact points of the post and rim joist, insert bolts through the post and rim joist but place 1/8" galvanized washers between the joist and the post. Create a gap of about 1/8" to 1/4".
To really do it right, before you drill the bolt holes, place a washer on the top outer edge of the rim joist and then rest the post on top before drilling. This will ensure a small gap exists when you secure the post in its final position.
This kind of deck railing detail should extend the life of your posts at least a few years. Learn more...
Surface Mounted Posts
This is a great option for wood deck railings because posts for wooden decks are always susceptible to moisture damage. Railing posts can be secured to a deck surface through the use of metal brackets or anchoring devices.
Here are a couple articles you should read to understand this option further...
If you want a wood deck railing system that you never have to worry about devoting a lot of annual maintenance to, consider each of these post installation methods. The choice is yours. Good luck building your deck railing!