The best approach to ensure a strong connection is to install unnotched rail posts flush to the inside or outside of the deck frame. 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.

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.

Another safe, cost-effective option is to use a deck post connector to attach deck-railing posts to the deck framing. Because the post is tied back into the deck joists, rather than to the rim joist alone, the connection is stronger than typical through-bolt installations and meets the International Residential Code ® (IRC) provisions for guardrail reinforcement.

Simpson Strong-Tie offers its DTT2Z deck tension tie that connects the railing post back into the deck framing and provides a safe, strong connection. It meets IRC building code standards that require deck railing posts to be able to resist a 200-lb. load in any direction. The connector fastens quickly and easily using Simpson Strong-Tie Strong-Drive® screws (SDS), which install without pre-drilling and are included with each connector. The DTT2Z also has a ZMAX® coating for additional corrosion protection.

For more information about deck connectors and fasteners, visit http://www.strongtie.com/deckcenter