Categories: Decks and Railings, Contractor Homeowner

Code-Compliant Guardrail Post Connections

Posted On: October 20, 2020

Posted By: Jim Coshow

"Today, we're chatting with our good friend Michelle Yee, territory manager for Simpson Strong-Tie in the Pacific Northwest. We appreciate Michelle working with her colleagues to put together this valuable article on installing safe and code-compliant guardrail post connections. Take it away, Michelle!"

- Jim Coshow

Deck railing posts are a critical point of connection to deck framing. Unfortunately, they are too often inadequately attached—and similar to deck ledger board connections, their failure can lead to catastrophic results. These guardrail post connections are also subject to a high level of scrutiny from building code officials, so knowing how to attach them properly will not only keep everyone safe, it will help keep your project on schedule. Let’s look at how to install them correctly.

Installing a guardrail post on an in-progress deck. — Photo credit: Simpson Strong-Tie

What is the code for guardrail posts?

IBC/IRC 2015/2018 requires guards and handrails to be able to resist a single concentrated load of 200 pounds applied in any direction at any point along the top.
The height of the guards shall be a minimum of 36” tall (IRC) and up to 42” tall for certain occupancies (IBC).

Through testing and analysis done by Simpson Strong-Tie, we are able to provide connectors and fasteners that can meet the 200-pound load requirement. Please refer to T-C-GRDRL20 by Simpson Strong-Tie for further information and installation instructions.

When installing a guard post to deck framing for a 36” railing, a DTT2 connector and the SDS fasteners that come with each part meet the load requirement with ease. Two examples of attaching guard posts to deck framing are shown below:

Two diagrams showing how to attach a guard post to a deck.
The first shows a deck from the side and points out DTT2 to joist layout and DTT2 to blocking layout. The blocking and deck joists are both 2x8 minimum.
The second shows a deck from the top, where rim joist meets band joist at a right angle. There are deck joists spaced out evenly parallel to the band joist. There is blocking evenly spaced out between the band joist and the first two deck joists parallel to the rim joist, and there is also blocking on the first and third deck joists. The diagram points out DTT2 to joist layout and DTT2 to blocking layout.

Image credit: Simpson Strong-Tie

For railings up to 42” tall, we recommend an HTT4 wood connector with Strong-Drive SD connector screws #10 for the highest load capacity. Below are two examples of attaching guard posts to deck framing for railings up to 42” in height.

Two diagrams showing how to attach a guard post to a deck.
The first shows a deck from the side and points out HTT4 to joist layout and HTT4 to blocking layout. The blocking and deck joists are both 2x8 minimum.
The second shows a deck from the top, where rim joist meets band joist at a right angle. There are deck joists spaced out evenly parallel to the band joist. There is blocking evenly spaced out between the band joist and the first two deck joists parallel to the rim joist, and there is also blocking on the first and third deck joists. The diagram points out HTT4 to joist layout. — Image credit: Simpson Strong-Tie

An alternative code-compliant solution for attaching guardrail posts to deck framing without the use of wood connectors and typical through-bolts is fastening the guard posts and framing elements with Strong-Drive SDWS Timber screws. The SDWS fasteners are code-compliant in the IAPMO UES ER-192. The solutions shown below have been tested and verified for 36” guard posts constructed with Douglas Fir/Larch, Hem-Fir and SP (Southern Pine) framing. These solutions have also been tested and verified for 42” guard posts constructed with Douglas Fir/Larch and SP (Southern Pine) framing only. Please refer to Simpson Strong-Tie T-F-GRDPSTRL18 for further details regarding use of SDWS for guardrail post attachments.

Diagram showing a screw with a .75" wide head and .22" wide body.

Rendering of a deck base. — Image credit: Simpson Strong-Tie

Thanks to Michelle for keeping us updated on these ever-evolving best practices! Check out some other great decking and fastener advice from Michelle in this article on ledger board attachment, and see an in-depth review of attachment systems in this handy wood screw guide.