Deck Rail Post Attachment

The best approach to ensure a strong connection is to install unnotched rail posts flush to the inside or outside of the deck frame. We recommend spacing your rail posts 6' apart or less.  Most builders use (2) 1/2" through bolts to attach 4x4 wood posts to the deck rim. Do not over tighten fasteners because it can crush wood fibers in the posts and greatly diminish the strength properties of the post. Some deck contractors have switched to structural screws in the place of bolts for rail post attachments. Such fasteners must be properly designed for your intended use and are approved by your local building department. The only code requirement states that the guard rail must resist a 200 lb. load along it’s top.

Lateral bracing brackets are available for rail post connections attached inside the frame. The bracket does a fine job of transferring the normal or perpendicular stress into parallel shear loads that work particularly well with bolts and can increase the load capacity from 400% to over 1500% over a notched rail post installation. Two brackets will be required for corner rail posts. Using this method will require you leave enough vacant space in the frame for the rail post and bracket to fit.

Generally, it is not recommended to notch posts guard posts where connected to the deck framing. This end of guard posts is subject to the greatest bending force, and cracking of the post at the notch is a common result. Fastening 4x4 posts at their full cross-section is proven to provide the best results and is strongly encouraged.