Important 2009 IRC Deck Code Revisions
Statistics have shown that more people are killed or seriously injured each year in deck collapses than any other single part of the house. To counter this telling statistic, it is vitally important that any deck construction be inspected and reviewed to ensure an utmost regard for customer safety. The 2009 edition of the International Residential Code has implemented a few changes, with deck safety at the forefront – focusing on ledger board attachment details.
The International Code Council (ICC) is a non-profit organization whose purpose is to develop a single set of comprehensive and coordinated national model construction codes. Ranging from building codes to fire codes to zoning codes, the ICC’s interest is in providing a comprehensive set of codes which facilitate uniformity across construction standards nationwide. Presently, ICC code is used, in some form, in all 50 states (for details on your state, visit http://www.iccsafe.org/government/adoption.html). The ICC releases updated editions of its codes every three years (2003, 2006, 2009, etc.). As 2009 coincides with the release of an updated edition, it is important to review the revised edition and be aware of any specific code revisions that apply to deck construction.
Before revision specifics are discussed in this article, it must be stressed that it is important for you to check with your local building officials to determine how revisions to the code are handled and when they will be adopted. Different municipalities have different methods of adopting revised code, and it is important to know how things are handled where you work to avoid any surprises, unnecessary construction revisions, or code violations.
The International Residential Code (IRC) covers the majority of the information relating to residential construction of outdoor structures such as decks. Fortunately, there are not a lot of changes in the 2009 code concerning deck construction, but the changes that are made are definitely noteworthy. The one that is sure to raise the most ire from deck contractors is the requirement of a minimum of two lateral load connections per deck (R502.2.2.3). Each of the connectors has the requirement of having an allowable stress design capacity of not less than 1,500 pounds. While contractors’ eyes tend to glaze over while reading this, their eyes tend to get a bit larger when viewing the added figure (Figure R502.2.3 of the 2009 IRC):
The figure reflects a bracket being mounted on a floor joist inside the home as well as a joist on the deck. These brackets are connected using a threaded rod. When the threaded rod is securely screwed into each set of connectors, it provides a rigid, lateral connection that meets the new IRC requirement.
This new revision in the 2009 edition of the IRC not only adds additional cost to the construction of EVERY deck (there are no restrictions or limitations on deck size), but may create a bit of additional labor and more pre-planning, especially if the deck is constructed a step lower than the house floor level. The IRC requirement is not specific as to the type of connector, so long as it has a 1,500 pound capacity. Currently, the only connector that readily conforms to the requirement is Simpson Strong-Tie model DTT2Z. The flier for the DTT2Z on the Simpson Strong-Tie at the Simpson Strong-Tie website has some great pictures and details. In addition to the DTT2Z, there are many different approaches to complying with this new requirement (including using other commercially available connectors in parallel), but all approaches should be analyzed by a licensed structural engineer before being implemented. Yes, this new requirement adds more cost and labor to the installation of a deck, but if it keeps a deck you built from collapsing, it is DEFINITELY worth the extra effort. A word of caution: don’t forget to leave some method for the inspector to visibly inspect the connection!
The second revision is inclusion of a table that provides a useful guideline when fastening a ledger board to the existing structure. While the ledger is typically installed with lag bolts or carriage bolts, there is no clear indication of how many fasteners are required for a satisfactory installation. Now, the new 2009 IRC table above provides the necessary details on how many fasteners are required based on the span of the ledger. Of course, the fasteners should be either hot-dipped galvanized or stainless steel. As with any table, the footnotes do provide valuable information, so it is important to familiarize yourself with those specifics as well.
In addition to the table found in 502.2.2.1, there are a few more revisions that are worth reviewing in the 2009 IRC. Section 502.2.2.2 makes the case that “girders supporting deck joists shall not be supported on deck ledgers or band joists. Deck ledgers shall not be supported on stone or masonry veneer.” To many deck contractors, this is common sense, but there are many new contractors in the trade who could benefit from these helpful requirements. Additionally, Section 502.2.2.1.1 outlines the specific allowable areas for placement of lag bolts in a ledger board:
The lag screws or bolts shall be placed 2 inches from the bottom or top of deck ledgers and between 2 and 5 inches in from the ends. The lag screws or bolts shall be staggered from the top to the bottom along the horizontal run of the deck ledger.
All of these requirements may, at times, seem to be overkill, but given the track record of residential decks, even small improvements in construction could lead to large gains in customer safety. With an estimated 50% of the decks in the country needing repair or replacement, the ICC’s Residential Code is something that should be studied and referenced on every one of your jobs – leaving both you and your customer with peace of mind.
For more information, consult the ICC’s International Residential Code 2009 (www.iccsafe.org) or Deck Construction Based on the 2009 International Residential Code (www.iccsafe.org) – a compilation of deck-specific requirements put together for experienced deck contractors by the ICC.
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