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Deck to 2nd story overhang

K

KLSRC

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Joined
Jul 11, 2022
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12
Location
Illinois
Hi everyone. I have someone who wants to support a deck off of a second story portion of a house that is cantilevered. In practice this has always been something that has been noted as a "no-no" but I do not see anything specifically prohibiting it in the code. We are on the 2021 IRC and do not have any amendments for decks.

Section 507.3 says that decks are to be supported on concrete footings OR "other approved structural systems designed to accommodate all loads in accordance with Section R301."

Since the existing framing of the house is partially unknown, my feeling is that this could only be approved if designed by a registered design professional who would verify the imposed loading on the existing structure is acceptable and would need to design for how to provide bearing for the deck framing.

Let me know if there's a better code section I am overlooking or if any of you have/would handle differently - thank you!
 

2021 IRC​

R507.8 Vertical and Lateral Supports​

Where supported by attachment to an exterior wall, decks shall be positively anchored to the primary structure and designed for both vertical and lateral loads. Such attachment shall not be accomplished by the use of toenails or nails subject to withdrawal. For decks with cantilevered framing members, connection to exterior walls or other framing members shall be designed and constructed to resist uplift resulting from the full live load specified in Table R301.5 acting on the cantilevered portion of the deck. Where positive connection to the primary building structure cannot be verified during inspection, decks shall be self-supporting.

R507.9.1.2 Band Joist Details​

Band joists supporting a ledger shall be a minimum 2-inch-nominal (51 mm), solid-sawn, spruce-pine-fir or better lumber or a minimum 1-inch (25 mm) nominal engineered wood rim boards in accordance with Section R502.1.7. Band joists shall bear fully on the primary structure capable of supporting all required loads.

Engineering design is required. Engineer will need to look at the moments acting on the cantilevered joists. Will also need to verify the connection of the rim-joist to the joist tails. Often this is just face-nailed. If hangers were used, they will have been installed in the correct orientation (supporting joists); however, the loading from the deck will be in the opposite direction. Rim hold joists up vs rim pulling down on joists.
 
KLSRC said:
Hi everyone. I have someone who wants to support a deck off of a second story portion of a house that is cantilevered. In practice this has always been something that has been noted as a "no-no" but I do not see anything specifically prohibiting it in the code. We are on the 2021 IRC and do not have any amendments for decks.

Section 507.3 says that decks are to be supported on concrete footings OR "other approved structural systems designed to accommodate all loads in accordance with Section R301."

Since the existing framing of the house is partially unknown, my feeling is that this could only be approved if designed by a registered design professional who would verify the imposed loading on the existing structure is acceptable and would need to design for how to provide bearing for the deck framing.

Let me know if there's a better code section I am overlooking or if any of you have/would handle differently - thank you!
Click to expand...
You are correct.
 
The definitions are out of the 2006 IBC. I do not know why they are not in the later editions since a balcony and a deck are not constructed the same.

BALCONY, EXTERIOR. An exterior floor projecting from and supported by a structure without additional independent supports.

DECK. An exterior floor supported on at least two opposing sides by an adjacent structure, and/or posts, piers or other independent supports.

TABLE R502.3.3(2)
CANTILEVER SPANS FOR FLOOR JOISTS SUPPORTING EXTERIOR BALCONYa, b, e, f
 
This would be my answer;
KLSRC said:
my feeling is that this could only be approved if designed by a registered design professional who would verify the imposed loading on the existing structure is acceptable and would need to design for how to provide bearing for the deck framing.
Click to expand...
 
classicT said:

2021 IRC​

R507.9.1.2 Band Joist Details​

Band joists supporting a ledger shall be a minimum 2-inch-nominal (51 mm), solid-sawn, spruce-pine-fir or better lumber or a minimum 1-inch (25 mm) nominal engineered wood rim boards in accordance with Section R502.1.7. Band joists shall bear fully on the primary structure capable of supporting all required loads.
Click to expand...
As one of the many professionals that worked together for the 507 provisions, this is how we addressed this question. As someone that continues to work on deck codes, I welcome any suggestions as to whether this is not prominent enough a statement to handle this application. I have been working for years on a re-write to the ledger and lateral load sections, which would include revising this section and language. I did not think this subject of band joist support needed to be better presented in the codes, but perhaps it does. Looking forward to more comments.
 
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