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Decks - 2015 IRC Code Highlights

Did you know that 2015 Code Sections relating to decks have been in place in Pennsylvania since December 31, 2015? (See L&I Website)

The above link will take you to the Department of Labor and Industry’s website where they list 2015 code sections that were adopted on December 31, 2015. If you glance through the International Residential Code 2015 Sections, most of what was adopted at this time was related to constructing decks.

And, since most residential contractors run into decks often, we thought that we would remind you of a few things that frequently get missed when submitting for a deck permit. So, here are 7 highlights from the 2015 IRC building codes relating to decks that are worth noting.

1. Lateral Load Connection

(R507.2.4). Unless the deck is freestanding from the house, a lateral load device is required in order to create a positive attachment between the deck and house to resist lateral loads. There are two common devices for addressing this requirement, and since there is an overabundance of information and illustrations available online, let me just refer you to Google. If you get really stuck, here is an example at

2. Concentrated Loads From Beams on Deck Ledgers – Not Allowed

(R507.2.1). Remember that deck ledgers cannot support concentrated loads from beams or girders. Instead, beams and girders must be supported by proper posts or another continuous load-bearing path down to the footings.

3. Deck Posts to Deck Beams

(R507.7.1). Remember, deck posts cannot simply be sandwiched between beam plies. Instead, beams must rest directly on the post and be secured against horizontal loads. A double beam can be bolted to a notched out 6x6, or beams can also be attached by manufactured post-to-beam connectors of proper size. Please refer to this entire code section for fuller explanation (See also AWC link below).

4. Deck Beam Spans

(R507.6). Don’t guesstimate beam spans! It is best to refer to an official table in order to determine the adequate beam spans for your deck. The 2015 Deck Beam Span Table is readily available online (2015 Table R507.6, included in AWC link below).

5. Sizing for Footings

Keep in mind that not all of your deck footings will necessarily be the same. For example, footings toward the middle of the deck will bear more weight than say an outside corner. Be sure to size each footing to an adequate diameter based on a calculated tributary load (Deck Load Calculator)

6. Sizing Provisions for Posts

Though it seems most builders are using 6X6 posts, it may be helpful to know that 4×4 and 4×6 posts are permitted up to 8′ in length - 6x6s up to 14′. These measurements are taken from the soil to the bottom of the beam.

7. Nailing Patterns for Putting Beams Together.

Let me just refer you to a helpful article regarding nailing a board together (

If you have built decks before, we hope the some of these highlights will help you to address at least some of the 2015 code requirements that are often missed by many, but if you are new to decks, there is a lot more to know than just these 7 items, so check out the American Wood Council link below for a prescriptive deck guide that is based on the 2015 International Residential Code before you submit your deck plans for a building permit.

Remember, you should always speak with your local building code official before you begin any building project as they can direct you to additional resources and potentially other requirements.

(Prescriptive Residential Wood Deck Construction Guide)

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