replacing cantilevered deck to post & beam


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Old 10-01-06, 09:52 AM
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replacing cantilevered deck to post & beam

I will be removing my cantilevered deck and replacing it with a post and beam design, and cutting back the rotted joists to the original house framing. Since the floor joists were cantilevered, there is no header joist or beam, only short blocks between the joists. Should: 1. the ledger board be attached with lag screws to the ends of the floor joists (leaving the short blocks in place behind the ledger board), or 2: should the joists be cut back an additional 1 1/2 inches to accept a header nailed to the ends of the floor joists, which would then be flush with the exterior of the house, and install the ledger board on top of that?
If the latter, how should the lag bolts be installed, since there won't be access to the inside once a new header is in place? Pre-install the lag bolts and countersink the nuts to keep them in place, and then attach the ledger?
 
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Old 10-01-06, 03:37 PM
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replacing cantilevered deck to post & beam

Have you considered a free-standing deck?

It eliminates many problems that you have with a ledger - leaks, rot, flashing, etc.

Using lag screws into the partially/possibly roted joists could be questionable.

Dick
 
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Old 10-01-06, 10:59 PM
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evesk,

I HATE cantilevered decks!! The joists are the weakest link in a deck. That's what's going to rot first, but the homeowner has no clue that it's happening until the deck boards themselves start showing their age. By then, it's too late.

Get rid of the cantilever. There should be NO connection between the floor joists of the house and the joists of the deck.

I agree with Dick -- lag bolting into rotten floor joists after you cap them with a ledger board is questionable, at best. Hopefully you caught the rot in time, BEFORE it got to the floor joists of the house.

Make the deck freestanding.
 
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Old 10-03-06, 08:49 AM
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Actually, the second floor is cantilevered over the deck by four feet, so that the joist section closest to the house has been protected and is still in good condition.
Also, at a distance of 8 feet from the foundation (where I would install 12" footings, 6"x6" posts, and a 2"x10" girder beam), the height is 12'3" from ground to the bottom of the joist at one end of the 45'8" deck, and 6' high at the other end.
My plan would be to cut the existing cantilevered joists flush with the foundation, leaving the short blocks in between the joists in place, and attach the ledger board with lag screws into the ends of the floor joists, in which case the new deck joists (16" o.c.) would have to be offset from the existing joists so the lag screws won't interfere. The ass't building inspector couldn't give me a definitive answer whether this would be structurally sound and acceptable ("talk to your architect").
This presents one more problem. I've read that the ledger is usually cut short 1 1/2" on each end, so that the rim joists could be attached to the ends of the ledger. That wouldn't work here, since the ends of the ledger would have nothing to attach to. I guess the ledger board would have to run the entire length to the sides of the foundation and the ends attached to the existing rim joists, in which case those lag screws would have to be countersunk, and the new rim joists installed on the face of the ledger board? Am I headed in the right direction? Thanks again.
evesk
 
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Old 10-03-06, 10:18 AM
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replacing cantilevered deck to post & beam

If you do go with a ledger, make sure it is PT and the house is properly flashed to prevent any moisture penetration and rot of the interior. Lack of flashing is the reason for most failures of attached decks.

PT requires special screws.

Dick
 
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Old 10-03-06, 06:10 PM
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evesk,

Lag bolting into the ends of your existing joists (after you cut them off) is weak. You would be better off reinforcing the freeze blocks between the joists and putting the lag bolts there.

As Dick (Concretemasonry) pointed out, PT (ACQ) lumber requires either stainless steel or hot dipped galvanized fasteners. And flashing!! Whatever you do, DO NOT use aluminum flashing if it's going to be in contact with ACQ. Vinyl flashing works well. EP tin does OK.
 
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Old 10-04-06, 06:32 AM
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lefty,

That was my suspicion about bolting into the joist ends. How does one reinforce the freeze blocks? It would seem to me that they too would be a weak link.

Thanks,
evesk

(P.S. Your previous post about cantilevered decks must have made Frank Lloyd Wright roll around in his grave).
 
 

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