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Thread: Deck Support

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    brianmiller's Avatar
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    Default Deck Support

    Do you all recommend diagonal/lateral bracing support for a deck constructed in this fashion, or would you let it go?

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    Last edited by brianmiller; 07-02-2013 at 05:25 PM.
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    Default Re: Deck Support

    Yes, it needs diagonal bracing.
    Also, it likely has improper connection to the house if it is brick veneer as opposed to solid masonry walls. Unless the brick was removed or added after the deck was installed, it is almost impossible to provide solid connection to the structure of the house. Brick veneer is not a structural element and it should not be used to attach the rim joist/ledger no matter how many anchor bolts used.
    If it is not a self supporting deck, that would receive a bad review from me.

    Jim Luttrall
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    Default Re: Deck Support

    Quote Originally Posted by brianmiller View Post
    thanks Jim...in this photo you can see no ledger board. Appears the joist are cantilevered out of the house; no way to know how the joists are connected to the house structure. I'll write it up as suspect connections.
    I would not be so quick to say "It's suspect"
    Doesn't look as though anything is wrong.
    If you write up everything you can't see, you must write up a lot.

    ' correct a wise man and you gain a friend... correct a fool and he'll bloody your nose'.

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    Default Re: Deck Support

    I agree with Rick, there does not appear to be a problem flashing turned out over the joists that appear to pass through the veneer. Looks good from a thousand miles away!

    - - - Updated - - -

    About the staining, no signs of rot or other deterioration, no mention in the report. If I know there is a strong likelihood that there is a condition that WILL cause a problem, then I will report with some recommendations. That however appears to be part of the natural aging process, nothing to report there from what I can see in the photos.

    Jim Luttrall
    www.MrInspector.net
    Plano, Texas

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    Default Re: Deck Support

    Quote Originally Posted by brianmiller View Post
    Good point, Rick.....

    Also, do you all make note of how the dark water staining on the pressure treated wood; no rot but it doesn't give me a warm fuzzy feeling that it won't become rotted out down the line.
    If the wood columns at the ends of the deck are continuous from the footings to the eave of the roof, that would be enough lateral support for me. With the flashing visible from below I would give the builder a little more credit on the attachment method he used and would not guess it wrong.

    Pressure treated wood decks get wet, how much of a fuzzy feeling do you need?

    The beatings will continue until morale has improved. mgt.

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    Default Re: Deck Support

    Quote Originally Posted by brianmiller View Post

    Now....the checking in pressure treated wood....how much is too much, acceptable?
    When something (checking) becomes a safety (structural) issue.

    ' correct a wise man and you gain a friend... correct a fool and he'll bloody your nose'.

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    Default Re: Deck Support

    Are those concrete pads laid on grade or are they several feet below grade - piers.
    Do the columns sit on the surface of the pads (piers) or do they go down into the pier?

    Checking is common in wood which has not been dried properly. Usually its of no concern, but pictures would be helpful.


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    Default Re: Deck Support

    Quote Originally Posted by Vern Heiler View Post
    If the wood columns at the ends of the deck are continuous from the footings to the eave of the roof, that would be enough lateral support for me. With the flashing visible from below I would give the builder a little more credit on the attachment method he used and would not guess it wrong.

    Pressure treated wood decks get wet, how much of a fuzzy feeling do you need?
    The deck is relatively small, but 4x4s that long could flex quite a bit. I would recommend lateral bracing unless I could not move the deck by pushing on the columns.

    When decking is split like that it often indicates that it is old or was not treated properly. I usually describe this as significantly split or heavily weathered and recommend replacement as needed.


  9. #9
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    Default Re: Deck Support

    Quote Originally Posted by brianmiller View Post
    Do you all recommend diagonal/lateral bracing support for a deck constructed in this fashion, or would you let it go?
    Every column that is longer than 2 feet need to be laterally supported. The columns shown in your picture ARE laterally supported... the question is... Are the lateral supports adequate? You can't just guess "YES" or "NO"... some calculations actually need to be done... and it is the job of an engineer to do that.

    One could say that the columns appear to be bulky enough to support the weight they are carrying but you can't stand there, as a home inspector, and state, right on the spot, that they ARE ok... or that they ARE NOT ok.

    I have the building code in .pdf format in my iPhone and can make a quick reference to the joist span tables when I see something that appears fishy during an inspection. However, one couldn't make reference to the code in this case. The columns are not typical and are not listed in the code.

    Because of the size of the deck, at least in my neck of the woods, a building permit would have been required to build this structure. I would note in my report that I recommend my client inquires with the vendor about whether or not a building permit was obtained. If so, you can assume that at least 2 competent individuals would have looked at it before you (the designer, and the city official who approved the building permit application). If the vendor can't produce a building permit for it, then it would lie on the purchaser to decide if he is willing to buy the property with the knowledge this structure probably was not designed properly by a competent professional... or to have an engineer approve its structural integrity... or, just walk away.


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    Default Re: Deck Support

    Lat support would be nice, just like using 6x6 instead of 4x4. But not necessary to build to a minimum code. Don't know local NM code though I expect that it meets the local code.

    The issue of what you can not see is always a concern. Footer depth, PSI of concrete, actual mechanical attachment hardware, What is going on behind the brick and so on. You could write a book of "what if" for the structure.

    Was the deck and roof built with house or added on? May be cantilevered off the house, and if so how far did it go back into house . Just can't say.


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    Default Re: Deck Support

    Good morning Alain,

    Every column that is longer than 2 feet need to be laterally supported
    Is that a local requirement? I am not familiar with that requirement.

    Thanks,


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    Default Re: Deck Support

    The deck cover may offer enough lateral support. I sometimes just rock my weight on the deck to see how stable it is. If it sways, I recommend additional lateral support. The staining on the framing looks normal.

    If you choose not to decide, you still have made a choice.

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    Default Re: Deck Support

    Quote Originally Posted by Raymond Wand View Post
    Good morning Alain,



    Is that a local requirement? I am not familiar with that requirement.

    Thanks,

    Was waiting for someone to ask that question. Thought it may have been a Canadian thing.


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    Default Re: Deck Support

    Quote Originally Posted by Lon Henderson View Post
    ......I sometimes just rock my weight on the deck to see how stable it is. If it sways, I recommend additional lateral support.....
    Like the daring young man on the flying trapeze?


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    Default Re: Deck Support

    hard for me to tell from the pic, at first I thought were 6x6 posts.
    Also, since attached to the dwelling (ASSuming proper), does that not constitute much of the needed lateral support, vs a free standing post supported structure in that not as much needed/required or at least with this deck would be adequate



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    Default Re: Deck Support

    Quote Originally Posted by Mark Reinmiller View Post
    The deck is relatively small, but 4x4s that long could flex quite a bit. I would recommend lateral bracing unless I could not move the deck by pushing on the columns.
    .
    Posts are considered to be too slender when their "l/d" ratio exceeds 50. So for a 4x4 the maximum height would be 3.5" x 50 = 175" = 14' - 7". For a 6x6 it would be 5.5" x 50 = 275" = 22' - 11". A 4x4 post taller than 14'-7" or a 6x6 taller than 22'-11" should have lateral bracing in both directions.

    I doubt that the deck joists are cantilevered, unless the posts carry through the deck without a beam at the outer edge supporting the joists. Plus, the joists span appears too great for a cantilever.

    From a design perspective, I would expect to see lateral bracing for a deck that tall as the metal post caps and bases provide no lateral support, but I don't think it is a necessary call for a home inspector.

    Last edited by Thom Huggett; 06-17-2013 at 05:38 PM.
    Thom Huggett, PE, SE, CBO

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    Default Re: Deck Support

    Many (but not all) AHJ require decks to conform to the requirements of the IRC's "Prescriptive Residential Wood Deck Construction Guide", based on the 2009 IRC . The latest version of the Guide is dated June 1, 2013, although the main difference between it and earlier versions is a more conservative series of allowable span tables.

    That document requires that any deck taller than 2' off the ground must have diagonal bracing. If the deck is partially/properly supported by the house, then the diagonal bracing is only required in the parallel (to the house) direction. The Guide also requires all columns (referred to as "posts") be at least 6 x 6 nominal.


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    Default Re: Deck Support

    Quote Originally Posted by BridgeMan View Post
    Many (but not all) AHJ require decks to conform to the requirements of the IRC's "Prescriptive Residential Wood Deck Construction Guide", based on the 2009 IRC . The latest version of the Guide is dated June 1, 2013, although the main difference between it and earlier versions is a more conservative series of allowable span tables.

    That document requires that any deck taller than 2' off the ground must have diagonal bracing. If the deck is partially/properly supported by the house, then the diagonal bracing is only required in the parallel (to the house) direction. The Guide also requires all columns (referred to as "posts") be at least 6 x 6 nominal.
    The guide is put out by the American Wood Council and can be found at: http://awc.org/publications/DCA/DCA6/DCA6-09.pdf

    Last edited by Thom Huggett; 06-18-2013 at 12:59 PM. Reason: Clicked twice...
    Thom Huggett, PE, SE, CBO

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    Default Re: Deck Support

    For what it's worth, according to the insurance industry this would be considered a porch because it has a roof. Regardless of who calls it what, I would think that would change the requirements considerably, particularly concerning whether diagonal bracing is necessary.

    The posts look like 6X6s to me.

    Last edited by Kristi Silber; 06-19-2013 at 11:51 AM. Reason: technical difficulties
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    Default Re: Deck Support

    Quote Originally Posted by Thom Huggett View Post
    Posts are considered to be too slender when their "l/d" ratio exceeds 50. So for a 4x4 the maximum height would be 3.5" x 50 = 175" = 14' - 7". For a 6x6 it would be 5.5" x 50 = 275" = 22' - 11". A 4x4 post taller than 14'-7" or a 6x6 taller than 22'-11" should have lateral bracing in both directions.

    I doubt that the deck joists are cantilevered, unless the posts carry through the deck without a beam at the outer edge supporting the joists. Plus, the joists span appears too great for a cantilever.

    From a design perspective, I would expect to see lateral bracing for a deck that tall as the metal post caps and bases provide no lateral support, but I don't think it is a necessary call for a home inspector.
    What you are saying is only partially correct. At an l/d of 50 the load carrying capacity of the 4x4 is greatly reduced, so it may not carry the tributary load. Also, this assumes no significant eccentric loading (there will always be some). And this is for laterally stability of a column loaded in compression. It does not take into account lateral forces on the deck. Lateral bracing needs will depend upon several factors, but I would specify bracing for a deck with columns about 5 feet tall (assuming the deck is attached to the structure and the size was modest).


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    Default Re: Deck Support

    The 'architect' might have left off bracing because of those windows. Didn't want to obstruct the view. IMO, diagonal bracing is needed. Make it look like you want it to stay put, overbuild it.

    Maybe big steel angle brackets would do the same thing as bracing. Steel columns bolted to footings would be good and strong. Rough timber looks best with diagonals, IMO.

    If that was on the side of a condo building here, it would have steel cross bracing added. Safety first.

    John Kogel, RHI, BC HI Lic #47455
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    Default Re: Deck Support

    All these rules for decks may not apply if this isn't a deck at all. It has a roof, so it's a porch. To ignore the roof is to ignore the bracing it provides through the posts that others have pointed out. Why would diagonal bracing be necessary? What would it add if the roof keeps the upper ends of the posts stationary? To me it looks like a well-made structure, as far as can be seen from the photos and providing the wall attachment is correct.

    According to dictionaryofconstruction.com a deck is "1. An uncovered wood platform usually attached to or on the roof of a structure."

    From Permitspace (which examines building codes in NYC): "Definition of a Deck:
    A Deck is a raised floor, supported by structural framing above the surrounding ground at the level of the first story of a house. A Deck must be constructed without a roof. An outdoor structure with a roof is not a Deck."

    And from a guide to porch and deck construction issued by the City of Chicago (http://www.leestreet.com/lease/porch...on-rules.pdf): "The Chicago Building Code defines a porch as “an unheated roofed portion of
    a building, generally containing a stair used for ingress (entering) and egress
    (exiting) and a floor area, and separated from the principal portion of the building
    by a fire rated wall and unrated doors and windows.” A deck is defined as
    “an open, unroofed structure used in conjunction with a principal building or installed
    on the roof of a building. A deck other than a rooftop deck may be classified
    as attached or detached depending upon its relationship to the principal
    building.”"

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