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  1. #1
    Shane Dredge's Avatar
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    Default Deck attached to overhang

    This deck is roughly 4 years old. House built in 2006. In this area, the 2003 version of the IRC rules (i use rule loosely) the land. I know that decks should not be attached to cantilevered structures such as this overhang window but what is there a specific code reference in the 2003 IRC to support this? I know there is verbiage pertaining to joist span and cantilever requirements but I can not find anything that specifically addresses "thou shall not connect a deck to a cantilevered structure". Any thoughts or assistance is greatly appreciated.

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    Default Re: Deck attached to overhang

    Quote Originally Posted by Shane Dredge View Post
    This deck is roughly 4 years old. House built in 2006. In this area, the 2003 version of the IRC rules (i use rule loosely) the land. I know that decks should not be attached to cantilevered structures such as this overhang window but what is there a specific code reference in the 2003 IRC to support this? I know there is verbiage pertaining to joist span and cantilever requirements but I can not find anything that specifically addresses "thou shall not connect a deck to a cantilevered structure". Any thoughts or assistance is greatly appreciated.
    You will find PDF#6 of great assistance.http://www.awc.org/publications/DCA/DCA6/DCA6-09.pdf.

    (see page 12)

    PROHIBITED LEDGER ATTACHMENTS
    Attachments to exterior veneers (brick, masonry, stone) and to cantilevered floor overhangs or bay windows are prohibited (see Figures 17 and 18). In such cases the
    Figure 17. No Attachment to or Through Exterior Veneers (Brick, Masonry, Stone)
    deck shall be free-standing (see FREE-STANDING DECKS).
    Figure 18. No Attachment to House Overhang


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    Default Re: Deck attached to overhang

    Quote Originally Posted by Shane Dredge View Post
    I know there is verbiage pertaining to joist span and cantilever requirements but I can not find anything that specifically addresses "thou shall not connect a deck to a cantilevered structure".

    You are looking for the wrong verbiage. You should be looking for the verbiage which says "Hey, Idiot, the cantilevered span is just that, and you have now INCREASED the cantilevered span, which means you either need to remove the deck or install proper support from the ground up to the deck where the deck attached to the cantilevered structure." (or verbiage similar to that ).

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  4. #4
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    Default Re: Deck attached to overhang

    Thanks for the input guys.


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    Default Re: Deck attached to overhang

    Quote Originally Posted by Jerry Peck View Post
    you either need to remove the deck or install proper support from the ground up to the deck where the deck attached to the cantilevered structure.
    I have pics here of a deck attached to a cantilever, but with support added to make it good. Not that hard, actually. Diagonal bracing would make it even better, but, hey.. I would have called for lag bolts through the ledger board if they're not there.

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    Default Re: Deck attached to overhang

    2006 IRC Section

    R502.2.2 Decks.
    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 as applicable. Such attachment shall not be accomplished by the use of toenails or nails subject to withdrawal. Where positive connection to the primary building structure cannot be verified during inspection, decks shall be selfsupporting. For decks with cantilevered framing members, connections 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.

    The fastening of the rim board to the cantilevered joists is by nails subject to withdrawal, but that can be overcome during framing by using upside down joist hangers to connect the joists to the rimboard before the floor sheathing is installed. Except that is not done 99.9% of the time.




  7. #7
    Shane Dredge's Avatar
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    Default Re: Deck attached to overhang

    I just got off the phone with the City Building and Codes office. Spoke to a code inspector... He told me that they would pass this deck the way that it is. Aggravating.


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    Default Re: Deck attached to overhang

    shane,
    i would also be concerned that the posts supporting the roof structure are bearing on a cantilevered rim joist. the post should bear on the lower girder or posts. piss poor design.


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    Default Re: Deck attached to overhang

    Shane

    Depending upon your original balcony configuration and loading the tables in IRC 502 will list your cantilever limit. Once you attach a deck the new equivalent cantilever length will be nearly 60% of the total span. This new cantilever length will now fall outside the tables in IRC 502.

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    Default Re: Deck attached to overhang

    Quote Originally Posted by Fred Weck View Post
    The fastening of the rim board to the cantilevered joists is by nails subject to withdrawal, but that can be overcome during framing by using upside down joist hangers to connect the joists to the rimboard before the floor sheathing is installed. Except that is not done 99.9% of the time.

    Why do the hangers need to be upside down?


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    Default Re: Deck attached to overhang

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  12. #12
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    Default Re: Deck attached to overhang

    Quote Originally Posted by Lisa Endza View Post

    Where? I couldn't find it.


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    Default Re: Deck attached to overhang

    You don't need to install joist hangers upside-down at their ledger board ends if the leverage of the cantilever lifting the deck up is limited by being no more than one-quarter the joist length or three times the joist width (nominal depth), whichever is smaller. This limitation creates a scenario where the leverage the cantilever applied to the deck, lifting it up at the ledger board, would be more than offset by the weight of the deck, holding it down. Now if you violate this formula and your cantilever is, let's say, one-half the joist length, well then you've created a seesaw and have to figure out a way of preventing the joists from being lifted out of their hangers at their ledger board ends.

    Last edited by Lisa Endza; 08-26-2010 at 10:11 PM.
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    Default Re: Deck attached to overhang

    How do you know the cantilever wasn't designed to support the deck ,just by virtue it's a cantilever ?. Refer to PE.


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    Default Re: Deck attached to overhang

    Quote Originally Posted by James Risley View Post
    I think he is not too clear in describing the upside down hangers. I assume he means that if you attach the deck to the overhang on the house then the downward load on the overhanging rim joist can be countered by installing upside down joist hangers on the far end of the joists which are within the structure. The downward pressure on the overhang rim joist would then held by the joist hangers preventing the lifting of the rear of the joists. This requires framing the rear wall to withstand the uplift and the rear wall would then require its own beam/joist to which the upside down hangers could be attached.
    JR
    Ding ding ding!!!


  16. #16
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    Default Re: Deck attached to overhang

    How far into the structural design of a house are home inspectors required to look? It may not be the case (I always assume the worst), but the cantilever could be designed to support the deck. You don’t have to rely on cantilever limitations in the code if a structural design is calculated. I am an architect, if I were to design a deck like this as an add-on I would have calculated the cantilevered joist and if they where insufficient it could be a relatively simple matter to insert additional joist to take the load. Was any of this done when the deck was added? Was the original floor cantilever designed to take the loads of the deck? Is it a home inspector’s job to sort all this out? If that is the case you need to re-calculate every beam in the place.


  17. #17
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    Default Re: Deck attached to overhang

    Right Tom !, If an HI see's something suspect structurally he should refer it to someone who has the proper knowledge to asses it. In this case a failure could result in significant damage and injury.


  18. #18
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    Default Re: Deck attached to overhang

    BTW, maybe the deck floor joists actually extend into the interior bearing wall and all you are looking at is blocking ?


  19. #19
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    Default Re: Deck attached to overhang

    Quote Originally Posted by Thomas Streicher View Post
    How far into the structural design of a house are home inspectors required to look? It may not be the case (I always assume the worst), but the cantilever could be designed to support the deck. You donít have to rely on cantilever limitations in the code if a structural design is calculated. I am an architect, if I were to design a deck like this as an add-on I would have calculated the cantilevered joist and if they where insufficient it could be a relatively simple matter to insert additional joist to take the load. Was any of this done when the deck was added? Was the original floor cantilever designed to take the loads of the deck? Is it a home inspectorís job to sort all this out? If that is the case you need to re-calculate every beam in the place.
    The deck was part of the original home build. There were ceiling tiles in the basement so I moved one and stuck my head in to see the cantilever for the overhang window. The overhang was about 3 feet and the back span was about 8 feet or so... Straight forward 16 inch centers with joist hangers. The deck was lag bolted to the band board on the cantilevered window and a small section was lag bolted to the band board for the house. The problem is that the window was properly cantilevered using the 3:1 ratio but when you attach the deck to the band board on the window you are screwing that calculation up because in essence you are extending the overhang with the deck. Remember the joists for the deck did not cantilever back into the house structure. The deck was bolted onto the house. During a visual inspection of accessible components, a deck attached to a cantilevered structure always throws up a red flag for me and that is why I have requested expert evaluation..... Always open to feedback.


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    Default Re: Deck attached to overhang

    Shane it may be difficult for us as Generalists to have an exact answer .

    1) The end of the deck is supported by posts making this not a true floating cantilever.
    2) The 3 left side joists are attached to the building and not the cantilevered section.
    3) The place was built in 2006 making this brick veneer so we have no idea how the left side ledger is attached ,or to what.

    Seems best practice would have been to have another set of posts at the wall but this would be hard for any of us not trained in deck design to figure.

    I would basically say as much in my report.


  21. #21
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    Default Re: Deck attached to overhang

    Quote Originally Posted by Shane Dredge View Post
    The deck was part of the original home build. There were ceiling tiles in the basement so I moved one and stuck my head in to see the cantilever for the overhang window. The overhang was about 3 feet and the back span was about 8 feet or so... Straight forward 16 inch centers with joist hangers. The deck was lag bolted to the band board on the cantilevered window and a small section was lag bolted to the band board for the house. The problem is that the window was properly cantilevered using the 3:1 ratio but when you attach the deck to the band board on the window you are screwing that calculation up because in essence you are extending the overhang with the deck. Remember the joists for the deck did not cantilever back into the house structure. The deck was bolted onto the house. During a visual inspection of accessible components, a deck attached to a cantilevered structure always throws up a red flag for me and that is why I have requested expert evaluation..... Always open to feedback.
    If the deck was built with the house there is a good chance the load for it may have been factored in, itís done all the time. If this building is only 4 years old there should be plans on file somewhere. If itís built per the plans that may be all you have to say about this. It sounds like you have a PE or architect looking at it. Let us know how that works out.

    BTW, a 3:1 ratio doesnít necessarily make it properly cantilevered and all the deck is doing to the load of the joist is adding a point load to the end.

    Last edited by Thomas Streicher; 08-27-2010 at 12:46 PM. Reason: add info

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    Default Re: Deck attached to overhang

    For give me if I am wrong here. A properly cantilevered area can be built up, as if the wall were carried by the foundation, Yes Or No? If so, attaching the deck should be no different, as long as the deck is not adding to the length of the cantilever. Be gentle with me,,framing is not my forte.


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    Default Re: Deck attached to overhang

    Quote Originally Posted by James Risley View Post
    I think he is not too clear in describing the upside down hangers. I assume he means that if you attach the deck to the overhang on the house then the downward load on the overhanging rim joist can be countered by installing upside down joist hangers on the far end of the joists which are within the structure. The downward pressure on the overhang rim joist would then held by the joist hangers preventing the lifting of the rear of the joists. This requires framing the rear wall to withstand the uplift and the rear wall would then require its own beam/joist to which the upside down hangers could be attached.
    JR

    James, thanks for the clarification, even though I disagree with the premise .


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    Default Re: Deck attached to overhang

    Quote Originally Posted by David Bell View Post
    For give me if I am wrong here. A properly cantilevered area can be built up, as if the wall were carried by the foundation, Yes Or No? If so, attaching the deck should be no different, as long as the deck is not adding to the length of the cantilever. Be gentle with me,,framing is not my forte.

    David,

    First I will make a presumption: "A properly cantilevered area can be built up, as if the wall were carried by the foundation, Yes Or No?"
    - You are asking if a cantilevered floor can have a wall and roof constructed on it? Right? If so, then, yes, provided the span and joist sizes are designed for that load.

    Now for a correction: "If so, attaching the deck should be no different, as long as the deck is not adding to the length of the cantilever."
    - As soon as you add a deck, or anything, to that cantilevered structure you are effectively lengthening the cantilevered joist lengths. Think of it this way: You add a 5 foot wide deck (which is not much of a deck) and one end of the joists are supported by columns and a beam, with the other end of the joists being supported by a ledger attached to the cantilevered structure. You are effectively carrying 2-1/2' of that 5 foot wide load on the columns and beam, and effectively carrying the other 2-1/2' of that 5 foot wide load on the cantilevered structure (presuming the loading is equal across the deck), that means you have effectively made the joists of the cantilevered structure 2-1/2 feet longer, and they were already likely are there longest allowed length.

    Here is another example to explain it: You hold a 10 foot long piece of 1" EMT with one hand, and it is a bit difficult with that leverage out there 10 feet. Now, get a friend to hold the other end of that 10 foot long EMT - it is a lot lighter, right? That is because 'you' are now only holding up 5 feet of it, your friend is holding up the other 5 feet. Now attach your end to a cantilevered joist - that joist is now holding up your 5 feet of it.

    I know one of our resident engineers can jump in here and correct and tweak what I am saying, probably even explaining it better than my basic explanation.

    Jerry Peck, Construction / Litigation Consultant
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  25. #25
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    Default Re: Deck attached to overhang

    Quote Originally Posted by Thomas Streicher View Post
    If the deck was built with the house there is a good chance the load for it may have been factored in, it’s done all the time. If this building is only 4 years old there should be plans on file somewhere. If it’s built per the plans that may be all you have to say about this. It sounds like you have a PE or architect looking at it. Let us know how that works out.

    BTW, a 3:1 ratio doesn’t necessarily make it properly cantilevered and all the deck is doing to the load of the joist is adding a point load to the end.
    Agree with the you regarding 3:1 ratio doesn't necessarily make it proper. That was what was visible to me at the time of the inspection. I also concur that the deck is not adding true "floating" cantilever load but is adding load from the portion of the deck that was attached to the house or point load. There are support beams at the yard side of the deck that carry some of the load down to the ground. Good points that I considered but did not articulate very well in my summary. My concern lies in that code prohibits attaching a deck to a cantilevered structure and based on what was visible, it did not appear that additional measures were taken to account for the "point load" of the deck being attached to the cantilevered window. I will update the post when I find out what the PE says. The city code director is going out on Monday to look at it also. They seem to be concerned about the way it is built now that they understand the reasoning behind my questions.

    Last edited by Shane Dredge; 08-27-2010 at 09:38 PM.

  26. #26
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    Default Re: Deck attached to overhang

    Quote Originally Posted by Thomas Streicher View Post
    If the deck was built with the house there is a good chance the load for it may have been factored in, it’s done all the time. If this building is only 4 years old there should be plans on file somewhere. If it’s built per the plans that may be all you have to say about this. It sounds like you have a PE or architect looking at it. Let us know how that works out.

    BTW, a 3:1 ratio doesn’t necessarily make it properly cantilevered and all the deck is doing to the load of the joist is adding a point load to the end.
    I am not an architect and legitimately do not know the answer to this question. Do house building plans ofter include or factor in plans for decks or are the house plans created and the deck is then added by the builder assuming that the builder will take into account fundamental building requirements / best practices? I have no idea. I would ASSume with the risk of making myself one, that the house plans might factor in a deck depending on how integral the deck is to the house but not all of the time. In the case of this house, it would seem odd to me that plans would call for all of those provisions for the deck as opposed to just making the deck free standing or adding vertical supports below the house side of the deck. Would that not be the simple and most sure way to accomplish the load distribution?

    Last edited by Shane Dredge; 08-27-2010 at 09:45 PM.

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    Default Re: Deck attached to overhang

    Quote Originally Posted by Jerry Peck View Post
    David,

    First I will make a presumption: "A properly cantilevered area can be built up, as if the wall were carried by the foundation, Yes Or No?"
    - You are asking if a cantilevered floor can have a wall and roof constructed on it? Right? If so, then, yes, provided the span and joist sizes are designed for that load.

    Now for a correction: "If so, attaching the deck should be no different, as long as the deck is not adding to the length of the cantilever."
    - As soon as you add a deck, or anything, to that cantilevered structure you are effectively lengthening the cantilevered joist lengths. Think of it this way: You add a 5 foot wide deck (which is not much of a deck) and one end of the joists are supported by columns and a beam, with the other end of the joists being supported by a ledger attached to the cantilevered structure. You are effectively carrying 2-1/2' of that 5 foot wide load on the columns and beam, and effectively carrying the other 2-1/2' of that 5 foot wide load on the cantilevered structure (presuming the loading is equal across the deck), that means you have effectively made the joists of the cantilevered structure 2-1/2 feet longer, and they were already likely are there longest allowed length.

    Here is another example to explain it: You hold a 10 foot long piece of 1" EMT with one hand, and it is a bit difficult with that leverage out there 10 feet. Now, get a friend to hold the other end of that 10 foot long EMT - it is a lot lighter, right? That is because 'you' are now only holding up 5 feet of it, your friend is holding up the other 5 feet. Now attach your end to a cantilevered joist - that joist is now holding up your 5 feet of it.

    I know one of our resident engineers can jump in here and correct and tweak what I am saying, probably even explaining it better than my basic explanation.
    I thought that was a great explanation assuming your logic holds water.


  28. #28
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    Default Re: Deck attached to overhang

    Thanks Jerry, You made it so even I could understand!


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    Default Re: Deck attached to overhang

    I would add an image of a sail catching the wind. The original cantiliever should have been designed to withstand uplift and sheer, i.e. wind resistance by extending it (the cantilliever as in a skinned deck) it is akin to enlarging a sail - thereby adding additional stressors such as when straight winds hit the house wall under the deck. The larger/deeper the "sail" (extension of the deck out from the wall) the greater increased stress on the "mast" (cantillevered attachment, and thereby the wall), think of a fulcrum/see-saw action - the further out from the pivot point the more amplified the force.

    It is clear from the photographs that the deck-level stairway landing area ledger is attached to or through the brick veneer and is otherwise unsupported. There are inadequate guards for the openings in the upper stairway area between steps.

    I suspect the "opinion" recently acquired from AHJ was undocumented, and limited in scope, and NOT based on the SECOND PICTURE.

    There are several things suspect as to what is pictured, especially the second (middle) picture. Furthermore the deck itself cantillievers beyond its own posts and is supporting (full gable or hipped?) roof cover structure at its most extended cantillivered edge. No cross bracing, downspouts positioned to washout, patio below and unremediated grade adjacent/behind will further undermine integrity. I see enough to question.



    Interestingly the smaller condenser is installed under this deck. I suspect there have been several modifications "improvements" to this overall area since original construction plans submitted, not only to the deck area itself but the area above deck/over head. I suspect post/columns and beam supports necessary between brick wall and area now occupied by condenser and cross bracing in both directions are needed.

    A plans check (architect or engineer's stamp for all these additions/modifications to original plans) and professional site visit and review would be a good idea. I seriously question/doubt the structural adequacy as built and presented here from what I do NOT see and should. Having benefit of unseen engineering/plan specifics, and what is structurally behind that brick, roof structure, etc. measurements and calculations would be necessary to determine precise remediations necessary.

    Last edited by H.G. Watson, Sr.; 08-28-2010 at 09:16 AM.

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    Default Re: Deck attached to overhang

    Quote Originally Posted by James Risley View Post
    A quick check, very rough and not necessarily definitive, would be to take a four or six foot level and see if the overhang is as level as the floor inside the structure. Specifically is the floor in the room "humped" any manner which would be indicative of bowing of the joists due to the downward pressure from the weight of the deck?
    JR
    We need to remember that the weight of the deck alone may not be that significant. The test would be the live load of +/- 30 people dancing on that deck.[:>0]

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    Default Re: Deck attached to overhang

    Quote Originally Posted by John Kogel View Post
    We need to remember that the weight of the deck alone may not be that significant. The test would be the live load of +/- 30 people dancing on that deck.[:>0]
    We know about that test all too well in Chicago.


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    Default Re: Deck attached to overhang

    The loads from that roof structure over and transfered to the deck structure and those of the deck itself are significant. The weight of materials is only a PART of the load calculations. Live loading involves more than the scaled weight of persons standing still.


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