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Repairing/Sistering Cantilevered Deck Joist

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  • Repairing/Sistering Cantilevered Deck Joist

    I don't know who thought that building decks/balconies this way was a good idea, but I'd like to kick 'em square in the nether regions.

    At what point does it go from being able to sister a joist to actually having to remove and replace the entire joist or cut 'em all off and install a ledger/post/beam?

    I know I need to be asking an engineer, because no one here wants to give structural advice over the 'net, and I don't blame ya'll. I'm just trying to figure out the best repair solution. Most of the joist only have 1/2" or so of rot along the tops, but there is one or two that are rotted 1"-2" down.The joists are untreated 2x12s the cantilever 8' out from the top plate.

    I would love to just cut all the joists back and install a ledger/beam/post, but not able to do it because of windows/decks below, so I'm stuck repairing or replacing this one.

    Also need to figure out whether the chimney was built cantilevered out over the deck, or if the put all the deck-boards down and built the chimney on top.

  • #2
    Re: Repairing/Sistering Cantilevered Deck Joist

    some more pictures

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    • #3
      Re: Repairing/Sistering Cantilevered Deck Joist

      I would recommend NEVER sistering new joists on a deck. If you've taken many decks apart, you probably know those areas are the first to start rotting, and will often rot in just a few years.

      If there is no other reasonable option, consider doing a few things;

      Put some type of spacers between the old joists and the new ones to minimize the possibility of rot forming, OR perhaps hanger the new ones between the wall and a preferably new rim board so they don't touch the old ones at all. Also consider scraping the old rot, and applying a rot repair epoxy product to prevent it from spreading.

      Just a few thoughts. Hope it helps.
      Michael

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      • #4
        Re: Repairing/Sistering Cantilevered Deck Joist

        By code, the framing HAS to be PT so you either have to start over or you have to put in a waterproof deck surface. Probably no slope now, so you need to rip 0-2" off the tops. And you GOTTA look for rot at and behind the line of the WRB. You didn't say was the spacing was, but it looks kinda like 24". If so, it feels under engineered already. And since the exterior portion is such a POS, I'd for sure want to know what the interior conditions are before I started touching things - verify interior length of joists and method of support and attachment.

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        • #5
          Re: Repairing/Sistering Cantilevered Deck Joist

          I noticed that it looks like the entire second floor wall is cantilevered over the first floor walls by a couple of feet too.
          Is that right?
          What a mess.

          Andy.
          Was a GC, doing drafting & design now.
          www.draftinginoc.com

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          • #6
            Re: Repairing/Sistering Cantilevered Deck Joist

            Have you already started work or did somebody else take off the decking?

            I don't see any a way to make that work without involving an engineer, alot of interior structural and probably some steel to make an 8' cantilever.

            Do you have some pictures of the whole view of this deck and the lower ones? Somebody may be able to give some design suggestions to incorporate a few posts through the lower area.

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            • #7
              Re: Repairing/Sistering Cantilevered Deck Joist

              When did gravity and physics change?

              I am constantly amazed at how things built 50 years ago that are completely non code compliant not only lasted, but performed well giving the methods.

              You really have to wonder how much of the overbuilding we do is overkill.
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              • #8
                Re: Repairing/Sistering Cantilevered Deck Joist

                Originally posted by Greg Di View Post
                When did gravity and physics change?

                I am constantly amazed at how things built 50 years ago that are completely non code compliant not only lasted, but performed well giving the methods.

                You really have to wonder how much of the overbuilding we do is overkill.
                Can you say 'Lawyer'. I have to admit, when you really need one, you really need one but...Damn! This is really out of control. I must say I have had more than my fair share of dealings with our legal system in a wide range of industries and situations but if I had my 'druthers' I'd do it all with a hand shake or a meeting 'out back' to solve most issues. Much quicker and the results are usually the same. Less the legal fees of course....
                Chuck Kiser
                Knollwood Construction Company
                Palos Park, IL 60464

                Knollwood Construction
                Kitchen Remodeling Chicago
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                • #9
                  Re: Repairing/Sistering Cantilevered Deck Joist

                  To answer a couple questions:

                  Yes, the entire 2nd floor wall is cantilevered out 2' from the 1st floor top plate,then the balcony extends another 6' out from that.

                  Another contractor took off the decking. For this HOA, like many others we work for, the deck boards are the responsibility of the homeowner, the HOA/property management company is responsible for the structure. This all started when the homeowner had her contractor come in to replace the deck boards. He removed a few rows and found the rot and stopped. That's when we got called in. I don't know who the other contractor is, or if he's even licensed. I have to wonder with the way he cut the deck boards out between joists. I would like to know what his plan is to replace the decking under the chimney too.

                  Looks like I'll be calling my engineer out to see what he can make of this mess.
                  Last edited by neubanksc5; 01-12-2012, 09:09 PM.

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                  • #10
                    Re: Repairing/Sistering Cantilevered Deck Joist

                    A redesign to make the decks self supporting might be one option. Would probably need to get an architect involved to get the asthetics reasonable so it doesn't look like a 'quick fix'/add-on. I imagine getting the HOA to agree would be a nightmare until the problem gets a lot worse.
                    HERS Rater • BPI Building Analyst • BPI Envelope Professional
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                    • #11
                      Re: Repairing/Sistering Cantilevered Deck Joist

                      The double 2x rim looks nasty, too. Esp with the front higher than the back.

                      Water trap.

                      Greg Burnett has a video on here somewhere with flashing details for wall/cantilevered deck joist. Might help you.
                      Last edited by S.Joisey; 01-13-2012, 03:03 PM.

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                      • #12
                        Re: Repairing/Sistering Cantilevered Deck Joist

                        I'd be curious to see that video. Anyone know where I would look?

                        I searched the site and forums for "Greg Burnett flashing" with no results.
                        -Ryan

                        Deck Building Contractor in Vancouver, BC

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                        • #13
                          Re: Repairing/Sistering Cantilevered Deck Joist

                          Well- to start, the only way to repair the cantilevers as they exist would be to remove the flooring to the interior to allow you to bring the new joists in to the house by some ration- 3-1 was the old standard. I'm not sure that you could install and fasten to the interior without doing that.

                          Greg- I agree that it's really not "underdesigned" structurally with the wood they used, but probably is if replacing with today's PT.

                          The other problem with the design is that, while it lasted however long (I doubt that building has been there for 50 years, but I get your point), because of the design what has to happen now is quite drastic. 50 years ago is roughly the '60s, it was really sometime in the '50s, post WWII when we were flush with victory and a belief in technology and the architects thought they no longer had to think about structure but were free to be pure artists (ala FLW) that this sort of design started coming about. There was certainly some in the '40s, and on occasion before that, but not as a common method of building. For one, not many people really thought they needed a deck, but also that meant difficult things like doors, and before that era people really did tend to think doors needed a roof over them. I often think the invention of hte aluminum sliding door as the genesis of this sort of deck.

                          So- it lasted, but it's going to suck to repair, be expensive and require either changes to the exterior or a lot of RRP to the interior.
                          http://www.lavrans.com

                          "He uses statistics as a drunken man uses lamp posts; for support rather than illumination." -Andrew Lang

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                          • #14
                            Re: Repairing/Sistering Cantilevered Deck Joist

                            Here is one.

                            Old was cantilevered 5'6

                            You can see we had to add a beam when re-doing the deck (we added another 6' as well).

                            I believe adding a beam is the easiest solution compared to going inside the floor framing. Whatever you have below just make it work. If you need longer spans talk to an engineer.

                            (I'm still interested in seeing that flashing video mentioned earlier....)
                            Last edited by Winchester; 03-12-2012, 02:51 PM.
                            -Ryan

                            Deck Building Contractor in Vancouver, BC

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                            • #15
                              Re: Repairing/Sistering Cantilevered Deck Joist

                              Looking at that design, I would never build anything like that or replace it in a like fashion. That space is little more than a private wood terrace that does not begin to approach what code today considers "balcony" area.
                              Neubanksc5, you have quite a project on your hands there. I would definitely involve an engineer in that one. My rule of thumb regarding cantilevers is max of 3' for 2x12 lumber with no structure above. A maximum of 1/3 out cantilevered and 2/3 anchored. I think you could sister to those, but it would be easier to go through a ceiling than a finished floor. There are flashing details you can use to alleviate the tendency for rot between sistered joists.
                              You can clean the existing joists and apply a preservative such as creocoat before sistering.
                              The condo association is going to assume the risk for the structure, so they need to approach this from the legal side and you should be ready with a structural solution for them.

                              IMO code values are there for good reason. typically the engineers get a failure limit under certain circumstances and the work backward from there to establish max loading. usually failure is 5 to 8 times max loading. Structures deteriorate over time and down the road costs for repair or liability are always much more. The load requirements are there as a "best compromise".

                              Phil
                              It's better to try and fail, than fail to try.

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