When it comes to deck construction, ensuring that your guardrails are both functional and safe is paramount. Often overlooked, the connection of railing posts, pickets, and balusters plays a crucial role in the overall safety and durability of the deck. This blog post will explore some of the essential aspects of deck guardrail construction, focusing on the importance of proper connections, minimum geometry dimensions, and code-compliant solutions.
Tag: deck safety
Decks Done Right Series — Real Solutions for Safer, Stronger Decks: Joists, Joist Connections, Beams, and Lateral Requirements
Deck Beams and Joists
Deck beams and joists need to be sized, spaced, and supported properly to support the loads that they are subjected to. The tables in 2021 IRC R507.5 list maximum beam spans for the different wood species members based on various ground snow loads. Table R507.6 helps to determine the maximum joist span, considering live load, wood species, joist spacing, joist size, and whether there’s a cantilever or not. Cantilevers are included but are maxed out at L/4. Joist spacing should be no more than 16″ o/c for decking that runs perpendicular to joists and no more than 12″ o.c. if the decking runs diagonal to them. DCA 6, Table 2 is the comparable section that addresses maximum joist spans and overhangs. These member sizes and spans are developed using established code minimum distributed loads of 40 psf live and 10 psf dead.
Decks Done Right Series — Real Solutions for Safer, Stronger Decks
The ledger is a crucial component in deck construction, serving as the wood member that attaches the entire deck to the house. Its proper installation is vital, as an improperly installed ledger is one of the most common causes of deck failure. This failure can result from inadequate or improper fastening to the supporting structure or from a failure to correctly flash the installation to prevent rot. Both issues can worsen over time, seriously compromising the integrity of a deck.
Building Safer Decks: Footings, Posts, and Post-to-Beam Connections
This is the second in a six-part blog series in which we discuss, from the ground up, how to build a code-compliant deck. Building a safe, sturdy deck involves much more than selecting the right materials and a stylish design. To ensure a deck can handle the loads placed upon it, a strong foundation is essential and starts with properly designed and installed footings, posts, and post-to-beam connections. Footings are the foundation of the deck, providing support to the posts, which, in turn, support the beams and the rest of the structure. Properly installed footings prevent settling or shifting that could jeopardize the deck’s stability. Post-to-beam connections are particularly crucial, as they bear the weight of the deck and distribute it to the posts. These connections should be reinforced with metal connectors to ensure they can handle the load. Now let’s get more into the specifics.
Building Safer Decks: Essential Tips for Code Compliance and Structural Integrity
Decks are a beloved feature of many homes, offering a space for relaxation, social gatherings, and a connection to the outdoors. However, despite their popularity, decks can also pose serious safety risks if not properly designed, built, and maintained. According to experts, decks cause more injuries and fatalities than any other part of the home’s structure — a shocking statistic that highlights the importance of ensuring your deck is safe, secure, and compliant with local building codes. In this article, the first in a six-part series, we’ll explore key insights into building stronger, safer decks, drawing on the thinking behind industry standards and guidelines.
Questions Answered: Deck Guard Post Connections Webinar
In this post, we follow up on our May webinar, Safer, Stronger Decks: Guard Post Connections, by answering some of the interesting questions raised by attendees.
Deck Guardrail Update
This post is an update to David Finkenbinder’s post on Guard Post Resources from August 13.
As David explained, the requirements in the IRC and IBC for guards are intended to prevent people from falling off of raised surfaces. The failure of this guard is a common source of injuries caused by failures of deck components.
Section R312.1.1 of the 2012 International Residential Code (IRC) states that “Guards shall be located along open-sided walking surfaces, including stairs, ramps and landings, that are located more than 30 inches measured vertically to the floor or grade below at any point within 36 inches horizontally to the edge of the open side.”
Table 301.5 of the 2012 IRC requires that guards and handrails be designed for “[a] single concentrated load” of 200 pounds “applied in any direction at any point along the top.”
David mentioned the article Tested Guardrail Post Connections for Residential Decks, which described a testing program at Virginia Tech that examined the ability of various assemblies to resist this concentrated load at the top of the guard post. But rather than test in any direction, the researchers decided to test in what they considered the most critical direction: outward away from the deck.
Simpson Strong-Tie subsequently developed a new tension tie, the DTT2Z, to make an economical connection from the top bolt in a deck post back into the framing of the deck to resist the high tension forces that develop in the top bolt when the top of the post is pushed outward. Several details were developed to try to address the various orientations of the post and deck framing.
To allow evaluation of assemblies used to resist this deck guardrail force, ICC-ES developed AC273, Acceptance Criteria for Handrails and Guards. AC273 is available for purchase through the ICC bookstore.
Even with the connectors being readily available, deck builders have asked for guard post connection details that do not involve the use of connection hardware. So Simpson Strong-Tie again tested several framing configurations according to the AC273 criteria, using our Strong-Drive® SDWS TIMBER screws and additional blocking to try to prevent the post from rotating. These details are shown in the engineering letter L-F-SDWSGRD15.
That brings us to the update part.
A committee made up of building officials, manufacturers, deck builders, designers and other interested parties is currently developing a set of code proposals on deck construction for inclusion in the 2018 International Residential Code (IRC). Even though more and more deck information has been incorporated into the last few editions of the IRC, there is still insufficient information in the code to be able to completely build a deck prescriptively. One area of interest is this guard connection. There is a desire to develop prescriptive details for both connection of a 4×4 post to deck framing with blocking and fasteners and for connecting the deck band joist back to the deck framing so that pre-manufactured guard rails can simply be fastened to the deck band with the knowledge that the connection is secure.
The problem is that, with the current requirement, the guard must resist the 200-pound load in ANY direction. All current testing, including AC273, only uses testing in the outward direction away from the floor of the deck. If the post were really required to resist a 200 pound load in the inward direction as well, then two hardware connectors would be required, one on each bolt. However, the belief of the committee is that resistance of 200 pounds in the outward and downward direction is primarily what is needed to ensure the safety of the occupants of the deck.
So they are working on a code proposal to change Table R301.5 of the IRC to require that the guard only resist the 200 pounds in the outward and downward direction and reduce the load to 50 pounds in the inward and upward direction.
The committee recognizes that while this is not necessarily a departure from current practice, it is a departure from current loading requirements in the IRC, IBC, and ASCE 7. So representatives of Simpson Strong-Tie met on September 30 with the NCSEA Code Advisory Committee – General Requirements Subcommittee to get the opinions of this group of active structural engineers. They provided valuable input, including the consideration that at some locations near landings and other changes in elevation, resistance to 200 pounds in the inward direction could be important.
Prior to incorporation of NCSEA’s input, the committee thought the code change might look as shown below.
We are interested in getting additional comments on this code proposal. What do you think? Let us know in the comments below.
d) A single concentrated load applied in any direction at any point along the top, in pounds.
f) Guard in-fill components (all those except the handrail), balusters and panel fillers shall be designed to withstand a horizontally applied normal load of 50 pounds on an area equal to 1 square foot. This load need not be assumed to act concurrently with any other live load requirement.
h) Glazing used in handrail assemblies and guards shall be designed with a safety factor of 4. The safety factor shall be applied to each of the concentrated loads applied to the top of the rail, and to the load on the in-fill components. These loads shall be determined independent of one another, and loads are assumed not to occur with any other live load.
j) A single concentrated load applied at any point along the top, in pounds. The 200-pound load is required to be applied in either the outward or downward direction, and it is permitted to be reduced to 50 pounds in either the inward or upward direction. The guard is not required to resist these loads applied concurrently with each other.
Wood-framed Deck Design Resources for Engineers
This week’s blog was written by David Finkenbinder, P.E., who is a regional engineer working out of the Simpson Strong-Tie Ohio branch which services 24 states through the Northeast, Midwest, and Mid-Atlantic. He graduated from Penn State with a B.S. in Agricultural and Biological Engineering in 2004 and earned his M.S. in Civil Engineering with a focus on Structural Engineering from Virginia Tech in 2007. His master’s thesis investigated the splitting strength of bolted connections in solid-sawn lumber and structural composite lumber. Since joining Simpson Strong-Tie in 2007, David has shown a passion for deck safety and has served on committees developing prescriptive information and building code provisions for decks. Here is David’s post.
“Decks cause more injuries and loss of life than any other part of the home structure. Except for hurricanes and tornadoes, more injuries may be connected to deck failures than all other wood building components and loading cases combined.”
This quote, taken from Washington State University’s magazine article Making Decks Safer, underscores the critical importance of proper deck design, construction, and maintenance. An engineer who is encountering their first deck may be surprised that the deck design resources available are not as plentiful as he/she might have expected. The following resources can be helpful start:
For decks built to the IRC, the book Deck Construction Based on the 2009 International Residential Code provides a review of applicable code provisions and related commentary. The book gives background on important durability considerations such as flashing at points where the deck connects to an adjacent structure. The book also briefly discusses variations with IBC provisions, which can be significant for examples such as minimum guard height and live loads.
The American Wood Council (AWC) has several tools available in addition to using the NDS for wood member and connection design. Calculators for evaluating simple span joists and single fastener connections are available in both web-based and mobile app format. Technical Report 12, which was the topic of our May blog post, provides the ability to design connections with a gap between members, or with members having a hollow cross section. AWC’s DCA6 – Prescriptive Residential Wood Deck Construction Guide presents information for common deck details and a commentary covering important considerations for alternate designs. While the guide is helpful, please note that it is limited in scope to single level residential decks and does not address wind or seismic design.
Researchers at Virginia Tech and Washington State University conducted laboratory testing and published information to help in several common topics needing attention. An article in the May 2008 issue of Structure Magazine featured test performance of ledger-to-band joist connections using bolts or lag screws – this information has since been adopted into the IRC.
For lateral design there has been some uncertainty regarding lateral loads that can be generated by occupants, and if the magnitude of such is significant in comparison with wind and seismic forces calculated from ASCE 7. Tests were conducted of occupants performing several types of movement on a deck floor configuration. Separate articles summarizing results for each load type were published in the Summer 2013 issue of Wood Design Focus, along with a fourth article on the lateral performance of IRC ledger attachments (online copies of the articles courtesy of Professional Deck Builder magazine: Wind Loads; Seismic Loads; Occupant Loads).
Our January 2013 post, Corrosion: The Issues, Code Requirements, Research, and Solutions, touches on the corrosion considerations that are significant for most projects as well.
Have you found any other resources that have been helpful in your designs? Let us know by posting a comment.
Who’s Thinking About Deck Safety? I Am!
A few months ago, the Today Show asked Simpson Strong-Tie to demonstrate a deck collapse to educate the public about deck safety. Often through the Fall and Winter months, decks go unused yet see a lot of activity from rain, sleet and snow. When the sun comes out in the Spring, people get out on their decks again without much thought about how the elements may have affected the important connections on their deck.
In addition to the weather, there are other factors to consider about deck safety:
- Experts agree that the average life expectancy of a wood deck is 10 to 15 years.
- It’s estimated that there are millions of decks in the U.S. that are beyond their useful life and may be unsafe.
- The number of deck collapses has increased in recent years.
- Within the past five years, 651 injuries and four deaths have occurred due to deck collapse.
So, I’m thinking about deck safety. I thought I’d share with you the “5 Warning Signs of an Unsafe Deck” we discussed on the Today Show:
Who's Thinking About Deck Safety? I Am!
A few months ago, the Today Show asked Simpson Strong-Tie to demonstrate a deck collapse to educate the public about deck safety. Often through the Fall and Winter months, decks go unused yet see a lot of activity from rain, sleet and snow. When the sun comes out in the Spring, people get out on their decks again without much thought about how the elements may have affected the important connections on their deck.
In addition to the weather, there are other factors to consider about deck safety:
- Experts agree that the average life expectancy of a wood deck is 10 to 15 years.
- It’s estimated that there are millions of decks in the U.S. that are beyond their useful life and may be unsafe.
- The number of deck collapses has increased in recent years.
- Within the past five years, 651 injuries and four deaths have occurred due to deck collapse.
So, I’m thinking about deck safety. I thought I’d share with you the “5 Warning Signs of an Unsafe Deck” we discussed on the Today Show:
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