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Dear Glenn: One Builder’s Headache With Deck Ledger Codes – Part I

DEAR GLENN: I’ve read many of your articles in JLC and I’ve watched videos on your website, too. You seem to be the go-to guy when it comes to deck construction. Maybe you can help me with my headache! I apologize if my rant is long (see below), but I’m hoping it’ll straighten out the issues for other builders, too. — Scott Wells – Scott Wells Construction Co., Medford, OR

A Note from the Publisher:

This article was originally written by Scott Wells, and we submitted it to Glenn Mathewson for his thoughts and feedback. For those of you who don’t know Glenn, he is a long-time tradesman, contractor, consultant and building inspector with significant experience in the field of code development and education. We decided to publish both Scott’s original article as well as Glenn’s responses as a two-part series; this first segment pertains to ledger attachments. Look for the next article on lateral load requirements soon!


It doesn’t seem to me like I’ve been in the construction industry that long. But when I see all of the continually changing code requirements I start to feel like I have. Many of the code changes are good and force the industry to build healthier, safer, and more efficient homes. But once in a while a code requirement comes along that I just don’t get. The lateral bracing requirements for decks is a perfect example. Those ever-changing requirements have become unnecessarily ridiculous. This is one of those times when too much of a good thing becomes a problem.


Photo courtesy of Simpson Strong-Tie (Note: Click any image to enlarge)

We’ve all seen the photos, YouTube videos, or read the stories: Overloaded deck. Improper flashing. Excessively rotten ledger board. Ledger attached with nails. Ledger attached to 3/4-in. OSB rim board. It seemed like every week or so, you heard a new story about a deck collapsing. And the main culprit: the ledger attachment. No doubt, something had to be done. It was time for the code makers to look at the way decks were being attached.

Here in southern Oregon, I’ve torn out or performed work on countless decks and seen several different ways that carpenters attached ledgers. Most are installed the same way: ledger nailed to the wall, sometimes right on the siding, or nailed right on the sheathing, with no flashing anywhere. What were they thinking? Usually the sheathing and siding are rotten and sometimes so is the rim board. Occasionally, I remodel a home and find a ledger was installed properly, with metal flashing redirecting water to the outside of the ledger, attached with lag bolts to a solid lumber rim joist, and maybe even with a planned air gap between the ledger and the home. But that’s the exception, not the rule. Here’s what I’ve been doing:

Glenn answers:

The contracting industry often looks at building codes as a thorn in their side, a government hurdle that must be cleared on each job, and throughout each job. While at times this is an understandable perspective, decks are a perfect example of what can happen to an industry, and a nationwide stock of structures, when there are no codes. The deck industry has been the Wild West since its inception—a place where lawmen are charged to administer laws that don’t exist, or are established only locally and partially. When decks have no codes, anything goes, which means that, from job to job and jurisdiction to jurisdiction, there was (and still often is) no consistency in what’s expected by the building authority. Codes provide consistency to contractors and clear and uniform rules for both builder and inspector. They minimize surprise. They keep all players in the game of construction accountable to the same set of rules. As we’re seeing in the news feeds, decks built without codes are now showing signs of age and poor integrity, and they’re often dying in catastrophic display.

I remember in the mid 2000s when the first wave of deck ledger code requirements surfaced. Suddenly building departments in my area required bolts for attaching ledgers to walls, and they specified metal “Z” flashings above the ledger and behind the siding. Clearly a sensible and reasonable improvement, even though I heard some carpenters complain about unnecessary and expensive code requirements. Those carpenters were obviously lazy and couldn’t have been more wrong. Hey, we’re in Oregon, man! It’s wet here and sometimes stays wet for months! This is not a good place to trap moisture! Rot will happen! Sure, it may take longer to remove or cut back some siding to slip flashing in. Sure, it may cost more to purchase lag screws. But this is the bare minimum for best practice. And “best practice” has become a key phrase for deck builders, or as the American Wood Council (AWC) puts it—”good practice.”

AIA Presentation-GMK-2_04-1

Notice that, according to the AWC, the flashing should extend past the joist hangers to help protect the hardware.

The history of the AWC is pretty interesting, especially if you’re in the deck business. Evolved from the American Forest and Paper Association, the AWC represents over 75% of wood products manufacturers. Their staff develops and promotes standards for wood products to ensure their best use. The AWC also “advocates for balanced government policies that affect wood products,” which is one reason they produce the Design For Code Acceptance manual (DCA-6), a graphic guide that really helps builders understand and incorporate often confusing code changes.

Rather than creating a new code, the AWC augments the IRC code; they pull together the best resources available—like the Fairfax County Typical Deck Details document, that enable builders to improve their practices. The DCA-6 is an all-inclusive guide, and many of their recommendations (and graphics) are used to develop the IRC code. However, the AWC reminds everyone that the IRC code always takes precedence, though DCA-6 includes provisions and details that are not found in the IRC.

Personally, I’d be lost without DCA-6, which helps me navigate the prickly IRC code and better understand the installation requirements for deck hardware.

Glenn responds:

When the three prominent publishing building code organizations across the US merged into the International Code Council and published the first IRC in 2000 (a 1998-IRC was published, but it was never mainstream), they included a paragraph prohibiting the use of nails “subject to withdrawal” for ledger connections. While good intentioned, a mere prohibition of one fastener orientation helped the decking industry about as much as the advice not to eat wild mushrooms would lead someone to a healthy meal. It prompted the end of ledger attachments with nails, but did not provide any guidance for a correct way to attach them. While it has its place in standards, prohibitive language alone does not suffice. Little changed in the first few editions of the IRC, and little changed in the potential hazard of decks built across the country.

The AWC recognized this problem and the wide assortment of locally developed deck standards throughout the US, and they decided that their sixth installment of their “Design for Code Acceptance” line of free publications would pertain to deck codes. Beginning with the 2006 IRC, it proved rather quickly to be their most successful DCA to date.

DCA documents provide ways to meet building code requirements. Provisions contained in DCA documents that are not included in the building code are considered good practice recommendations. Many building officials look to the DCA-6 as a means to approve deck construction, and the state of Georgia even legally adopted an amended version as the state deck code. Many provisions from the DCA-6 were later incorporated into the 2015 IRC, where decks are now much more comprehensively addressed than in any previous model code in history.

A few years ago, deck ledger fastening requirements, introduced in the 2009 IRC, were enforced in my region. We were given a “Fastener Spacing for a Deck Ledger” schedule that made a lot of sense and gave us some guides for ledger fastening, which was a big help and a boost to our industry.

Since 2009, new timber-type screws, like Simpson Strong-Tie’s SDS and FastenMaster’s LedgerLOK have also became available options (when approved by local building officials). Pre-drilling separate pilot holes for the rim board and ledger in order to install lag screws has become a thing of the past. These new types of fasteners can be simply installed with an impact driver following the manufacturer’s specified layout.

AIA Presentation-GMK-2_16-1

Ledgers can also now be spaced off the wall with stacked washers or Deck-to-Wall spacers, providing an air gap so ledgers can dry out and prevent rot. AIA Presentation-GMK-2_07-1

In 2012, the IRC made major changes to the bolting requirements.

AIA Presentation-GMK-2_15-1

In fact, the new guidelines for ledger fastening are so complicated, I can’t understand how anyone in their right mind thought contractors would be able to meet them. I sure hope the folks in southern Oregon never adopt that part of the code!

Glenn answers:

In 2005 a wood research team out of Virginia Tech acknowledged the need for a recognized method of attaching a deck ledger to a wood-framed floor and they set out to test it. With limited research funding, they tested the best variety of attachments they could and then they published an article on their findings. By 2009, the IRC was eager for a code solution and, during their hearings, they reviewed a proposal based on the Virginia Tech research that involved a simplified ledger-fastening table. While this was legendary research for the deck industry and a much-needed addition to the IRC, there is an inherent challenge in the nature of codes based on testing: the codes will be limited to the exact method of testing, and any deviation will not yet be proven—it’ll be much more risky for an authority to approve. For ledgers, decks went from Wild West to dictatorship, and it’ll still take more time to iron out wrinkles and create a well-represented democracy when it comes to ledger codes.

After publishing the 2009 edition, the AWC noticed many of the ledger connection stipulations were not in line with the engineering standards in the well-recognized and IRC-referenced document, the National Design Specifications (NDS). So the AWC submitted a code modification that was approved for the 2012 edition, but ultimately it created a bit of a mess. The NDS is a document for engineered design, not tested design. Without testing, one must make conservative generalizations of past experiences and gained knowledge, and this is represented in engineering standards, such as edge distance for fasteners. Merging the tested results from Virginia Tech with the edge distance requirements of the NDS design document quite frankly resulted in code that is unusable to both builder and inspector, as seen in this video:

But that’s not the only ridiculous code requirement….

In the next article, we’ll look at lateral load requirements, and not on handrail but on the ledger and joist diaphragm.



14 Responses to “Dear Glenn: One Builder’s Headache With Deck Ledger Codes – Part I”

  1. Mike Guertin

    In one big way the IRC deck code section hasn’t changed much since the first edition. In the 2015 IRC the opening section for decks says “Where supported by attachment to an exterior wall, decks shall be positively anchored to the primary structure and designed for both vertical and and lateral loads.” Similar language has appeared in previous IRC versions. The only thing the ICC did in the 2009, 2012 and 2015 IRC versions was add prescriptive methods for designing and building decks to meet the vertical and lateral loads.

    When you take apart that code sentence “Where supported by attachment to an exterior wall….” you realize that most of what confounds deck builders today – the ledger fastening schedule, fastener orientation to the ledger and rim board, and the lateral load connection drawing – only applies if you connect the deck to the wall of the house. When a deck is built to be self-supporting those code challenges are eliminated.

    The code has some other gifts for deck builders when you dig deeper. In chapter 4 you’ll find that the deck footings don’t need to be installed below the frost line – when the deck is self-supporting. So no matter where you’re building, the footings can be a blob of concrete just scratched 12 in. below the surface. And look at chapter 1 to find that you don’t even need to get a building permit for decks up to 200 sq ft (10 ft x 20 ft) provided it is 30 in. or less off the grade and not connected to the house.

    But then there are all the other ‘gotcha’s in the code that aren’t compiled in the 7 pages dedicated to deck construction in Chapter 5 of the 2015 IRC. Glazing, landings, stairs, handrails, HVAC exhausts, electrical equipment clearances, electric outlet requirements, illumination, dryer exhausts, siding clearances, emergency and escape routes, and more sprinkled throughout different sections of the IRC all pose code challenges that many building officials don’t focus on (yet). And then there are the references to other standards like ASTM D7032 that deck builders may have to comply with.

    It will be very interesting to see what comes of the current (2018 IRC) code hearings and what new prescriptive provisions will be added for deck builders to sort out.

  2. Mike Gandy

    Scott that’s an interesting flashing you used over the ledger. I wonder if it still traps water and will accelerate rot of the deck board. I have an issue with flashings over the ledger directing water right at the first deck board. A little north of you on Vancouver Island we get a ton of rain and level areas are a serius problem.
    Recently I have been attaching ledgers similarly to you with the spacers on the back of the ledger but I make them out of P/T material 2″ wide with a point on top and the height of the ledger (similar to a FHB article by John Spier#172). The structural fasteners go through the spacer 16″ o/c and penetrate 3″ into framing. Engineers here in seismic country have been good with this.
    The big difference with my detail is I install a tall flashing first that extends from 6″ above ledger to the bottom of the ledger with a kick out on the bottom to get the water away from the building. It normally turn out to be 14″ high and now the water runs right behind the ledger and out. The P/T spacers get attached to the building through the flashing with a single fastener and a bit of sealant similar to how you do it in the center of the joist spacing rather than behind a joist. Then the ledger gets bolted on through the spacers as is typically done. The gap between the decking and siding is a clean look with the flashing up behind by 4″ which you can detail from above with your weather barrier as you typically would with a window or door head flashing.
    The result is clean, no level or trapped areas for the water to sit and no peel and stick membranes exposed to uv. My two cents. Thanks

    • Giovanny Hernandez

      I’ve been thinking about doing the behind the ledger board, but I’m confused on what size nails to use when attracting the joist hangers to the ledger board. I’m reading that the nails should be 10d or 16d size nails. Which would be fine without spaces between house rim and ledger board. But spacers, those nails will penetrate the ledger board and maybe a half inch onto the house rim joist, making room for water penetration without any real structural strength (at least that’s my thinking). So now I’m wondering if I should avoid spacers and or keep them but maybe used smaller nails to attach the joist hangers. Thanks for any advice.

      • Scott Wells

        Giovanny,I assume that you’re using Simpson products for your decking hardware, and I’ve run into this same problem.  My solution of choice, for your situation, is to use Deck-To-Wall Spacers behind the ledger, and then use Simpson joist hangers (make sure your get the hangers that are not going to corrode if you’re using treated lumber) to connect the joists. For the angled fasteners, I like to use the 10D (hot dipped or stainless) nails specified (if they penetrate the back of the ledger – it won’t be by much), and the Simpson structural hardware screws (1-1/2″ long +/-)  for the connections in the face of the hanger.  That way I get a beefy fastener that doesn’t penetrate through the back of the ledger and into the rim of the house. Hope this helps.

  3. Brian

    I live in the north east and we have mostly brick veneer exteriors with 2×4 or 2×6 stud walls. I never see much written about how to attach deck or porch ledgers to these types of construction.

    • Todd Murdock

      You will find a lot of great information available in the DCA-6 (Linked to in this article) on code compliant deck construction and ledger attachments. If you look at figure 17, it specifically prohibits that type of ledger attachment: “No Attachments to or Through Exterior Veneers (Brick, Masonry, Stone).”

      Although there may be engineered solutions available, building a free-standing or “non-ledger deck” is probably the most economical solution. Be sure to check with the AHJ for any local requirements.

      Here is another link to the DCA-6:


    • Mike Guertin

      There’s a new device made for mounting ledgers to houses with brick veneer – the BR Brick Bracket.

      The inventor is a deck builder. He has the engineering for the system. As I understand it, since there is no ICC-ES criteria for a system like this there may not be an ESR for a while but users can present the test report to a local official for approval.

      I have a box of them but haven’t tried them yet. They’re primarily for new construction but you could cut out the brick and retrofit them.

      Another system that has been around for years is the Maine Deck Bracket . Again, a device invented and manufactured by a contractor. It’s not specifically intended for use with brick veneers but the ledger plate stands far enough off the wall to permit the brick to slip behind (usually).

  4. Kate

    Hello, I have an existing deck with without a ledger board, the deck joists are directly hung from a doubled 2×12 sill. While at a blush, this seems structurally sound enough (lags drilled through the double sill almost as if this was a ledger board and lateral connections), I am concerned about the waterproofing for the long term (no rot found to date). Is there a way to add some type of liquid waterproofing membrane so I do not need to trim all of the deck joists, add a ledger, and re-attached everything? or is this a case where I should definitely go back and add the ledger board and flashing? Is there a code requirement that mandates there be a ledger board if the deck is attached to the house?

    • Scott Wells

      Kate, I’m not sure if a deck ledger is a code requirement where you live, but I believe a ledger separating the deck framing from the house framing is best. That being said, if no rot is detected in your situation, I would recommend a couple of simple solutions to keep your deck joint/house rim area DRY. First, I’d suggest installing a 3″x3″ drip metal above the deck framing (and behind the siding and housewrap) that would re-route any water coming down the wall away from the house rim. Secondly, and you already mentioned it, a liquid flashing may be needed to help keep the house rim dry. I’m assuming that you have no protection at the rim now, such as housewrap or siding. You could spread liquid flashing (such as Zip System Liquid Flash) over the rim/joist connection to protect the rim from moisture. Liquid flashing is not too pretty to look at, so plan on covering it up with siding or blocking or something if this connection will be visible from anywhere. Hope this helps.

  5. Glenn

    Hello, my wife’s family has a house down in Cape Cod. I recently replaced the deck boards with composite ones. The framed deck structure seemed in reasonably good shape and everything looked to code. However, the builders of the deck offset the ledger board from the house using ledger deck wall spacers. I did some research and found this to be not very common but not unheard of either. There is a physical 2″gap between the house cedar shingles and the ledger board to allow any moisture & rain water to pass on down. What concerns me is they attached the spacers right over the existing cedar shingles. My concerned is when it come time to replace the shingles. I guess the only thing to do is replace around where the spacers are attached to the older shingles and flash and seal around the spacers. Any other suggestions?

    • Scott Wells

      If and when you decide to replace the shingles, it seems like you could do just what you thought of already, which is to flash and seal around the existing spacer, or you could remove each ledger bolt, one at a time, and replace the cedar shingles with a block that’s the same thickness. And, since the block is there just to take up the space of the removed shingles, make the block out of Boral Trim or pvc – something that won’t rot. Flash and seal the new backing block, reinstall your spacer and anchor, and move to the next spacer/shingle connection. Just a thought. Good luck.


  6. Steve

    I have a deck that was built over 30 years ago which is not compliant with the current IRC code. For the most part, it was well built and probably met code back then but was never permitted. We now need to get a CO for it asap. The problem is ledger is only 2’x6″ and the current code requires the ledger to be no less than 2″x8″. Is there anything that can be added that would allow the 2″x 6″ ledger to remain that would strengthen it up to what a 2″x 8″ ledger provides? The joist spans from the beam to the ledger are only 8′. We’re in a frost zone and the deck is less than 3′ above grade so adding another beam with posts and 3′ deep concrete footings is not a viable option.

    Thank you,

  7. Scott Wells

    As long as the deck and it’s components/hardware are not rotting or in disrepair, I would imagine that a reasonable inspector would allow you to add some lags screws or some timber screws to the leger/wall connection, some Simpson Deck Tension Ties to reinforce the lateral load, and some joist hangers. If all of that is a “no go” with your inspector, you can always cut the existing ledger out, replace it with a new 2×8, and add all of the above. This would be a total pain in the butt and totally possible.
    Good Luck.


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