Cantilever deck repair

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Old 10-09-15, 08:47 AM
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Cantilever deck repair

OK, let me try to frame up the issue: i have a 2nd story cantilever deck (~5'x10') on the back of my house. The structure is untreated 2x10 (i assume pine) sistered to the 2nd story floor joists, with 2 exterior joists (one on either side) for each interior floor joist. I'm assuming the 2/3 in, 1/3 out rule of thumb is in use here and that the joists are 16' with 5'ish exposed, but can't be positive. Since its untreated, the deck is clearly intended to be water tight from above, though clearly it is not - leaks abound. Obviously, the exterior structure is even with the interior 2nd floor structure, but the build-up of OSB, roll shingle and decking puts the exterior finished surface even to or above the sill/door leading out to the deck. Not good.

Short of lopping the whole thing off, i'm trying to remediate the situation without major surgery, or at least as little as possible. The best idea i can come up with is to rip a couple inches off the top of the exterior portion of each joist so that i can lower level of the deck, then re-roof, flash and shingle the structure.

So...

A) is this a terrible idea?
B) if not, i obviously would also want to reduce the length of the exterior portion of the joists, as they would be roughly a 2x8 instead of 2x10. What would be a safe remaining length? Since i've reduced the height of the joist by 20%, also reduce the length by 20%? It seems like the length is already over-extended for 2x10, but not sure how the doubling on each joist affects that determination.

rough sketch attached is not exactly to scale, though yes, that last set of joists is unevenly spaced, as opposed to the rest.

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Old 10-09-15, 12:23 PM
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As the interior also has subfloor, decking and finished floor covering, the difference between inside and out should be minimal. I suspect that the deck has been subsequently retrofitted with another layer of something to stop previous water problems. Have you excavated down to reveal all the layers on the deck?
 
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Old 10-09-15, 01:34 PM
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Difference is minimal, but troublesome nonetheless. Given the alignment of surfaces, it does not appear that i can effectively flash the joint of house to deck-top. There has been no major retrofitting, just apparent re-caulking/sealing that at the shingle/house joint that has subsequently failed.

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Old 10-09-15, 01:59 PM
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Tough one. Have you considered raising the door a few inches? You'd have to build a platform on the inside, but that may be easier than what you propose. If you raised it 4 inches it would give you a fighting chance at flashing.

Regarding your proposal....how bouncy is the deck now? Is there any diagonal bracing under the deck back to the wall now? Could you add some? Even if it was at a shallow angle it would add a lot of strength.
 
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Old 10-09-15, 02:23 PM
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Yeah, tough! Raising the door would be painful, i'd have to replace the whole thing (8 foot wide elaborate, custom door and casment set) with a more custom, shorter setup, as i can't go up any higher in the wall without dong major surgery...

Deck doesnt seem bouncy at now, though i don't have much room below for diagonal support - the deck is directly over the 8ft back door/windows, so there's not much room between the bottom of the deck and the top of the door below.. Probably 12"
 
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Old 10-09-15, 02:57 PM
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While we think about this, how about adding some pictures to help us out. A visual could assist and/or keep us from needless suggestions that are not feasible.

I'm leaning toward the need for a pan under the door that leads further out under the deck boards to prevent wicking. Pan would be a custom bend. Is the OSB dry or wet?
 
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Old 10-10-15, 09:49 AM
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Sorry czizzi, didnt get home until after dark.. Here's some pics of what i'm up against. Today i will demo down to the joists and include some more pics if i see anything that may be helpful.. If by wet OSB you mean that it is water damaged, then yes, there are several spots where it is rotted through.Name:  IMG_20151010_111750.jpg
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Old 10-10-15, 09:57 AM
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Are you positive that the cantelever boards are not pressre treated? Highly unusual that they would not be, and secondly, OSB has no place in that mix. How may hundreds of screws go through the membrane providing access for moisture to get to the OSB. So I guess the membrane is original to the house? How old is the property?
 
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Old 10-10-15, 05:16 PM
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Joists are definitely not PT.. Painted for the poor man's waterproofing, but that's it.. The very end of one of the joists is soft, so i'm going to have to shorten it one way or another.

The house is about 150 years old, though this deck is almost definitely part of a major remodel/rebuild that happened back in 2002 (i've had the house for 5 years). So i'm guessing the whole deck is 12 or 13 years old. The osb and membrane were in decent condition, except along the edge of the house where that seam failed, and around several shingle nails that leaked.
 
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Old 10-10-15, 06:44 PM
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If it is like most rot and water damage, the more you dig into it the worse it will get. SO many times I have started small projects that turned into major repairs.

Bud
 
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