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Old 08-23-2013, 02:38 PM   #1
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Sagging Deck


My brother's deck has a noticeable sag and he asked me about coming up with a solution for the sag and the bouncy feeling it has due to the overly long projection.

As can be seen in the photos below, there is a noticible sag in the middle of the span which is 12'. The support posts on the outside are 4" steel. There are 4 total on 8' centers along the outer 24' dimension. The deck joists are 2x8's and appear to be in good condition as does the anchorage to the house. The decking was replaced a couple of years ago and is in good shape.







We figured the best way to add support to the deck would be to run a sistered beam along the length parallel with the house. I was thinking about using a couple of 2x10's for this....something like this:



If we go with 4" round steel posts like he has now, what's the best way to secure the new beam to the existing floor joists and to the post caps?

I think using 4x6 posts notched out for the beam to sit in/on would be better, but I think he's stuck on using steel for some reason.

Finally, how large/deep should the footings for the posts be? The house is in Atlanta, GA.

Any other advice would be appreciated.
Thanks!


Last edited by Brickster; 08-23-2013 at 02:43 PM.
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Old 08-23-2013, 03:24 PM   #2
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Sagging Deck


Not seeing a whole lot done right on that one. None of that would have passed inspection in my area.
A ledger can not just be attached to a brick fascia.
The joist are undersized for that span.
No joist hangers were used.
There's no double rim joist.
Your local building inspector should be able to tell you what size and depth the Sono tubes need to be.

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Old 08-23-2013, 04:16 PM   #3
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Depth of footing is a local requirement, check with your local building department.

Size of footing and other information in regards to beam sizes, joist spans, etc. can be found in the "Prescriptive Residential Wood Deck Construction Guide" as published by the American Wood Council. This guide is based upon the requirements as found in the 2009 International Residential Code.

I'd review the requirements and construction as outlined in this guide. it should help to provide you with proper guidance.

It appears the existing deck does not have a supporting beam at the outside edge of the deck, the 12' span for the joists are at the maximum span previously allowed for preservative treated southern pine 2x8 joists at 16" o.c. Installing a drop beam (cantilevered joists) as your propose will help to strengthen the joists.

Post back with any questions. Good luck!
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Old 08-23-2013, 04:17 PM   #4
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Thanks for the replies.

While his deck certainly has some flaws, moving forward it seems that with the drop beam will fix the biggest complaint which is the shaky feeling the deck has due to the long spans.

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Old 08-23-2013, 04:44 PM   #5
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There's also no diagonal bracing to stop it from swaying and with those steel post I'm not even shore how you could add them.
I sure would not use 4 X 6's when you add supports, use 6 X 6's instead with the proper Simpson base and beam ties.
No notching needed, just install them under the double beam.
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Old 08-23-2013, 05:00 PM   #6
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Jack up the joists - before you put the beam in!
(A lot of sag on those joists!)
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Old 08-23-2013, 09:09 PM   #7
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Yeah, I need to figure out the best way to get things picked up before the beam is installed. I was thinking about picking up the outer band once it's disconnected from the posts, securing it with temporaries at enough height to compensate for the sag in the joists, installing the beam, and then letting the outer band down on the post caps.

I still like the idea of a notched post (6x6) instead of having the double 2x10 propped up on top of the post with hardware.

Sound good?
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Old 08-23-2013, 09:57 PM   #8
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Sagging Deck


I'm not sure how valid your idea of disconnecting the rim joists from the posts is. If the posts are concreted into the ground I think you may be better off putting up you knew being with temporary supports and checking those supports up a little at a time. That would probably help straighten out the joists quicker. It would also allow the deck to be used during the process which couldn't be done if you disconnected it from the steel posts. After you have the deck level like you wanted it you could measure and install the permanent new posts to support the beam.
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Old 08-24-2013, 12:06 AM   #9
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I had considered that, but the deck is 12'+ off the ground, so working at that height may be troublesome. My main concern with that method would be keeping the side of the beam vertical while it was being jacked up. I suppose the hangers would keep it in place while it was being picked up, but I'm somewhat out of my element with doing that. I've installed literally tons of steel columns that had to have some jacking done to get them into place, but I've got a lot less experience dealing with wood.
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Old 08-24-2013, 03:50 AM   #10
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Be careful when working on that----could you post a picture of the attachment to the house? That looks like a 2x4 ledger with the joist resting on it----jacking that up might lift the deck off the ledger---

Your brothers deck looks dangerous----
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Old 08-24-2013, 05:33 AM   #11
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Quote:
Originally Posted by oh'mike View Post
jacking that up might lift the deck off the ledger--
I agree...It doesn't look like anything more than nails are holding it to the house.

I can't see getting that much sag out of that deck without breaking something.
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Old 08-24-2013, 05:45 AM   #12
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Sad to say, that was dangerously built----please be careful---there is a lot more wrong with that than a sag----
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Old 08-24-2013, 07:30 AM   #13
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Sagging Deck


If there is as much sag as what it looks like in the first photo, I don't think you are ever going to get those joists straight again. I think you would have to remove the decking, sister in new joists, just a little higher than the existing ones, and re-install the decking.
If the biggest problem is the bounce, then the added beam should work.
The brick on your house is veneer, not structure. Hence the concern for how it is attached to the house.
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Old 09-12-2013, 01:00 PM   #14
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Yes, the biggest problem he has with using the deck is the bouncing, which I aim to rectify with the double beam down the middle. At this point, he wants to move forward with the beam reinforcement to get a few more years use out of the deck and then build a new one at a future date.

Although it cannot be seen in the photos, the deck is trough bolted to the framing of the house and not merely attached to the brick fascia.

If we were to pay someone to put in the double beam supported by four 6x6's and anchored on footings with Simson hardware on the bottom and hangers on top to secure the beam to the floor joists, how much would that run for labor roughly? Basically adding what is in this photo?


Thanks for all the help!

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Old 09-12-2013, 01:13 PM   #15
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That will certainly help--there is not enough lateral bracing on that deck---so plan on adding Y- braces to each post---this will add a lot to keep the deck from moving and swaying.

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