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403.1.4 minimum depth

Discussion in 'Residential Foundation Codes' started by rktect 1, Jul 15, 2010.

  1. rktect 1

    rktect 1 Gold Member

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    Well, today we had a person who was caught with a brand new deck built in his backyard. About 15'x20'. No columns, beams or concrete piers. In fact he built a rectangle 15'x20' with 2x8's and infilled the area with 2x8 joists at 16 inches on center. It is floating (is supported entirely) over/by the existing concrete patio. So I got to thinking that I had read about free standing decks somwhere and lo and behold I came across section 403.1.4 which we amended to read 42 inches below the undisturbed ground for foundations. This led me to 403.1.4.1 frost protection and on the very next page to the exceptions #3. "Decks not supported by a dwelling need not be provided with footings that extend below the frost line." And the funny thing about these decks, in this particular townhouse subdivision, is that their association rules specifically state that no deck is allowed to be directly attached to the dwelling which was written back in (guesstimate) 1980. It's funny because the deck serves as his required landing outside his patio door and by todays code, that landing shall be attached to the dwelling per 311.2.1

    So can the guy keep his free standing wood deck or have him remove it?
     
  2. pwood

    pwood Platinum Member

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    don't you have bigger fish to fry? i would kiss it off with the codes you cited.
     
  3. mtlogcabin

    mtlogcabin Sawhorse

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    Don't get hung up with Section 311.2.1 requiring what you have to be attatched to the dwelling. It is not raised off the ground, supported by the dwelling unit or post or piers or columns. If the deck heaves will it block the patio exit door ( assuming the door swings out) if not let it stay, charge him the permit fees and move on. If the door may be blocked due to frost heave discuss your concerns with the owner. If he has been there any length of time he knows if the patio has heaved in the past. Permit it with a condition that you reserve the right to monitor it thru the winter and if the problem arises he will have to correct it.
     
  4. rktect 1

    rktect 1 Gold Member

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    It would be easier if I were not only the plans examiner but the inspector. As it is I have gone over these sections with the inspectors and we have come to the same conslusions as stated above. We will accept the permit for the deck and inspect it. But I don't really do something I can't get my inspecotrs on board for. If they said no way, it's no way. I have to prove my case basically.
     
  5. peach

    peach Sawhorse

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    he could have thrown down some plywood over the slab.. move on.
     
  6. Yankee

    Yankee Sawhorse

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    I agree, it's fine.
     
  7. north star

    north star Sawhorse

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    * * *

    rktect1,

    While your scenario may not meet the actual wording and application

    of the code, I too agree with the others on here... don't lose a lot of

    sleep over this, ...or create a new ulcer or something. Permit it

    and move on!

    It has been, and continues to be, my experience that If the deck

    has been there for any length of time, usually [ not always ], it is

    almost impossible to have them remove it.

    FWIW, if possible... learn to pick your battles, and not every battle

    [ issue ] needs to be fought.

    * * *
     
  8. Uncle Bob

    Uncle Bob Sawhorse

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    RKTect,

    I'm not so sure that this should be ignored. The next time your inspectors drive by that home; there will most likely be a roof above that floor.

    Concrete slab-on-ground (3 1/2" thick); R506; is not designed to carry a permenent structural load (like a deck); and does not require a footing.

    The flooring of the deck should be supported by footings not less than 12" in depth per R403.1 (regardless of the frost line); and 12" wide per table R403.1.

    And if piers are used for the footing; the footings should be spaced to accomodate the load of the deck.

    When a homebuilder built a new home with a concrete patio (without footing) ; we made a note on our inspection forms (for the permenant record) to avoid problems of patio covers being built without proper support; and sure enough within a year or two; the owners were buiding wood frame roofs over the patios.

    I believe your inspectors are well aware of this; and, are not in favor of allowing the "deck" to be placed on the patio (slab).

    R301.1 requires all loads to be safely supported thought the "load-resisting elements to the foundation". The slab-on-ground is not designed to carry structural loads (the deck) in accordance with R301.

    Hope this helps,

    Uncle Bob
     
    #8 Uncle Bob, Jul 16, 2010
    Last edited by a moderator: Jul 16, 2010
  9. Yankee

    Yankee Sawhorse

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    I agree with UB's scenario but there are many times when we are pretty sure what will happen later and want to base our requirements on that experience, but I would caution against that approach, just make a note to the file and also try to speak to homeowners in advance of the construction (haha), and have them choose to plan for a future scenario.
     
  10. Uncle Bob

    Uncle Bob Sawhorse

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    Yankee,

    I probably shouldn't have added my scenario. A deck is a very heavy dead load; and I believe it must be supported by more than a 3 1/2" slab.

    Uncle Bob
     
    #10 Uncle Bob, Jul 16, 2010
    Last edited by a moderator: Jul 16, 2010
  11. Yankee

    Yankee Sawhorse

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    No, I would agree that the slab maybe "should have been" a compliant slab-on-grade with turned down footings depending on the code year it was built. Even given that, the slab is existing and I don't know that I would have required any additional concrete work for the deck joists to be built on the slab.
     
  12. peach

    peach Sawhorse

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    if it breaks the existing slab.. so?

    if it's typical patio slab construction, it's not attached to the structure, and neither is the deck.. it sinks into the soil.

    IF they build something on it, there may be a problem. I'd ask the question... if you want to invest that much time.
     
  13. bgingras

    bgingras Sawhorse

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    This is where common sense enforcement of the code comes in. It's essentially resting on the ground, it's not going to pose a hazard to life safety, is it? A lot of what we should be looking for is life safety, or safety to the building. Does this "structure" pose a danger as it's built? We cannot required things based on what someone "may" do down the road. We can note what we observe, put it in the file and call it a day. If we all want to cover our bases, agree to issue a permit for the structure contingent on the owner submitting an affidavit that no additional structure will be built on top of this deck. When/if they move towards building something else, you'll have an affidavit to hang your hat on when you refuse to issue permits without them providing the proper footings.
     
  14. peach

    peach Sawhorse

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    good answer, grasshopper gingras..
     
  15. Yankee

    Yankee Sawhorse

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    : ) lol

    this software won't allow one to be brief!
     
  16. bgingras

    bgingras Sawhorse

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    lol, thanks. I'm preparing for a second round interview this week and trying to practice answers just like that one. :)
     

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