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  1. #1
    Join Date
    Jul 2019
    Location
    VA
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    Default Attaching a deck to the house

    Did a house today where a new deck was supported with 6 x 6 posts up against the house so it was independently supported which is a good thing. But it was attached to the house with some small Tapcon masonry screws and not your typical 5/8 inch lag screws or lag bolts. Since it was independently supported, does the standard method of attaching it to the house still apply or was the method used acceptable?

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  2. #2
    Join Date
    Mar 2007
    Location
    Fletcher, NC
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    28,036

    Default Re: Attaching a deck to the house

    Quote Originally Posted by Robert Huffman View Post
    Did a house today where a new deck was supported with 6 x 6 posts up against the house so it was independently supported which is a good thing.
    If it independently supported, it should be free from (not attached to) the house ... unless the footings meet the following as applicable - in VA, I would presume the applicable section would be R507.3.3 Frost protection as there is likely a frost depth specified in Table R301.2 ... "I presume" as some jurisdictions don't seem to address Table R301.2 as thoroughly it should be: (bold and underlining are mine)
    - R5078.3.2 Minimum depth.P
    - - Deck footings shall be placed not less than 12 inches (305 mm) below the undisturbed ground ground surface.
    - R507.3.3 Frost protection. P
    - - Where decks are attached to a frost-protected structure, deck footings shall be protected from frost by one or more of the following methods:
    - - - 1. Extending below the frost line specified in Table R301.2
    - - - 2. Erecting on solid rock.
    - - - 3. Other approved methods of frost protection

    Jerry Peck
    Construction/Litigation/Code Consultant - Retired
    www.AskCodeMan.com

  3. #3
    Join Date
    Oct 2014
    Location
    Maryland, DC, and Northern Virginia, electrical only
    Posts
    445

    Default Re: Attaching a deck to the house

    Color me bloody ignorant:

    Electricians have means to compensate for thermal effects on conduit, and even to some extent for ground heave. We can use expansion fittings, expansion-deflection fittings, and sometimes just free-enough bends to supply slack and to take it up. (And yes, enough wire has to be able to slide in and out too.)

    Are there comparable systems used to flexibly stabilize a structure such as a deck against a house, if they move with respect to each other seasonally?


  4. #4
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    Mar 2007
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    Fletcher, NC
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    Default Re: Attaching a deck to the house

    Quote Originally Posted by david shapiro View Post
    Are there comparable systems used to flexibly stabilize a structure such as a deck against a house, if they move with respect to each other seasonally?
    There is, and the code covered them.

    If a house is constructed on, say, a basement foundation about 6 feet below grade, with a frost depth of 2 feet, making a minimum depth for a foundation of 3 feet below grade (12 inches below frost depth), with an elevated deck with its foundation on grade, the movement between the two will try to rip bolts out of the deck or out of the house.

    Make the deck self-supporting and free-standing. No need to attach it to the house.

    With electrical raceways and expansion joints, the two sections are designed to slide up and down within the expansion kount fitting.

    For a deck attached to a house and using an expansion connection, the fasteners would need to be able to slide up and down, one within the other, while also providing lateral support across the face of the wall, and while also providing perpendicular support holding the deck to the wall.

    A '+' fitting wouldn't work unless there was no lateral movement (for vertical movement), or unless there was no vertical movement (for lateral movement).

    I suppose that a large enough circular attachment could be designed to accommodate for up to the maximum calculated movement combinations of vertical and lateral movements, but then it would still need to be captive to restrain perpendicular movement.

    Definitely nor as easy as allowing for parallel movement of one piece within the other piece.

    Jerry Peck
    Construction/Litigation/Code Consultant - Retired
    www.AskCodeMan.com

  5. #5
    Join Date
    Oct 2014
    Location
    Maryland, DC, and Northern Virginia, electrical only
    Posts
    445

    Default Re: Attaching a deck to the house

    What you say makes sense, Jerry. (Imagine that.) Even in my field, I know how to calculate the need for an expansion fitting versus multiple expansion fittings, but I've never looked into figuring expansion-deflection fittings, where the mechanism is not just cylinder-sliding-within-cylinder. Has anybody here used those?

    For deck-to-house connection, I was imagining something like spring steel straps.


  6. #6
    Join Date
    Mar 2007
    Location
    Fletcher, NC
    Posts
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    Default Re: Attaching a deck to the house

    Quote Originally Posted by david shapiro View Post
    ... cylinder-sliding-within-cylinder. Has anybody here used those?
    I have, and I have seen them quite often on installations I've inspected. They serve their purpose and need for that expansion quite well.

    For deck-to-house connection, I was imagining something like spring steel straps.
    I'm not sure a "strap" of any kind would resist the necessary forces in all directions while also allowing movement in every direction.

    What I envision of a spring steel "strap" would only allow movement in one, possibly two, directions, but doing so would also give up its ability to resist unwanted movement in those directions.

    Jerry Peck
    Construction/Litigation/Code Consultant - Retired
    www.AskCodeMan.com

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