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Old 06-07-2012, 01:21 PM   #1
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Please Help With My Existing Deck


So, I've bought a house and am in the process of "beefing up" the existing deck, which really scares me. I'm listing info for the deck as is & current plans for "beefing up".

As is: The deck dimensions are 10' out from the house and 16' parallel to the house. It is built as follows. 2x8 ledger attached to the house, 2x8 10' out from house, then, spaced on 24" centers spanning 16' are 2x8. Yes, I said it correctly, the joist are PARALLEL to the house!! There are qty 3 of 4x4 posts notched on the outside most 2x8 of the box(one on each end and one in the middle). Decking material is 2x6 boards. There are 4x4 posts on top of the deck, supporting the railing and extending up to 2x4 rafters for a stick built roof with tin top.

Needless to say, there is quite a bit of "bounce" in the middle of the deck.

Beefing up: I plan to add joist hangers to all the existing joists and tie everything up tight. I'm doubling the number of joist by installing additional 2x8s to achieve 12" centers. Also going to double the 2x8 on the outside band (to help with support the 4x4s down from the roof). I also plan to build two frames underneath the deck, composed of a horizontal 4x6 and qty 2 vertical 4x4 posts (deck is approximately 6.5 feet above a concrete patio underneath). Each frame will be installed perpendicular to the house and 3 ft in from each end of the deck. Essentially creating a 10' center span with a 3' cantilever on each end, with 2x8 joists on 12" centers.

Any comments/suggestions/improvements?? Am I over/under building? I just want to be sure that I'm not overlooking something.

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Old 06-07-2012, 01:41 PM   #2
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Please Help With My Existing Deck


So if I'm reading you right, this deck is 10x16 with a rafter system above the deck with a tin roof for shade?

Since you are basically doubling up the joist/support for the deck, plus still have the above attached roof/shade system, I'd be a little concerned about all the weight sitting on 3 4x4 posts. Even though the posts sound like they are only 5 feet apart, it's the fact they are only 4x4's which would concern me. With that much structure now with the additional joists, etc, I'd be using 6x6 minimum for posts.

Just a thought though.

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Old 06-07-2012, 01:48 PM   #3
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You are correct that the deck is 10 x 16 with a rafter system & tin roof for shade.

The 4x4 posts are currently 8' apart (and 6-7' tall). Which is not sufficient. I plan on leaving the existing 3 posts across the outside, then adding 4 more 4x4 post under the deck (with a 4x6 beam supporting joists).

I also forgot to mention, I'm in central Alabama, so snow isn't an issue. The material is all #2 pine.
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Old 06-07-2012, 04:57 PM   #4
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a few photos would certainly aid in providing you with useful answers ....
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Old 06-07-2012, 05:00 PM   #5
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in case you don't have a copy of this I'd recommend downloading and reading through the Prescriptive Residential Wood Deck Construction Guide. http://www.awc.org/publications/DCA/DCA6/DCA6-09.pdf

it is based upon the 2009 International Residential Code and provides cookie cutter solutions for proper code compliant deck construction.

Can provide more info once we see the photos
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Old 06-08-2012, 07:55 AM   #6
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I'm attaching a photo I have from the home appraisal and a sketch of the deck as built.

I'll grab some more photos this afternoon.
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Old 06-08-2012, 08:33 AM   #7
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Please Help With My Existing Deck


Your deck is well below standards for a new deck based on current International Residential Code (IRC) guidelines. It would be quite expensive to bring the deck up to standards, since the posts are undersized, I am guessing the footings are undersized, the joists are undersized, the railings don't seem to meet code etc. So that leaves you with an interesting situation.

If you don't need to meet code, i.e. you don't need a permit, what is left to decide is what work you want to do, and exactly why you want to do it. There are a few possible ways to decide your priorities. One would be safety, you might be concerned that the deck could collapse, in which case you would want to repair or replace the most obvious safety issues, which would start with the railings (don't want anyone leaning on the railings and falling off the deck), then move to the joists, and eventually examine the posts. The joists could be sistered, or replaced with larger joists.

Or you could repair based on aesthetics. Maybe you don't like the sag in the deck, in which case you need to deal with the joists first. Your call, but there is little likelihood you are going to make this deck code compliant without tearing it down and starting over.
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Old 06-08-2012, 08:48 AM   #8
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Quote:
Originally Posted by piper131 View Post
I'm attaching a photo I have from the home appraisal and a sketch of the deck as built.

I'll grab some more photos this afternoon.
that deck is seriously over spanned/underbuilt. for example, according to the awc link posted above, a double 2x8 outer band/beam can only span 5' 7" with 16' joists hanging onto it before additional post support is needed and your double 2x8 spans 10'
without seeing how the deck is framed, maybe that is a triple beam or quad beam holding the joists but even that only covers 7' so you are still 3' short. I am really interested to see also how the beam is attached where it meets the house, no posts etc...

it looks like your 2x8 joists will be overspanned as well even when adding a new one every 12". you probably want to jack up/lift the joists that are there now and sister a 2x8 to them ( double them up) and nail the sister joist really well. Then add your other 2x8 every 12", that might get you a floor that does not bounce and is safe. you will certainly need to fortify the current post situation with larger posts.

Last edited by hand drive; 06-08-2012 at 08:50 AM.
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Old 06-08-2012, 08:55 AM   #9
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There are no double or triple 2x8 on this entire deck. there is no beam under the joist anywhere. Just the 3 4x4 post notch to have the 2x8 box set on them. The plan is to double up outside the band and install two built up 4x4/4x6 frames (to the patio below) 3 foot in (perpendicular to the house) from each. This is to bring the joist span to 10 ft between the frames, with a 3 ft cantilever on each end.

Also, anyone want to guess if anything was said about this deck in the home inspection?

Last edited by piper131; 06-08-2012 at 08:58 AM.
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Old 06-08-2012, 10:43 AM   #10
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Please Help With My Existing Deck


I don't think your issues here are related to your columns, but rather the floor construction.

Quickly calculating loading on the (3) 4x4 posts appears that they are of adequate size. With a deck 10x16, or 160 square feet, and figuring a 50 pounds/sf for live load and 10 pounds/sf for dead load, you are ultimately looking at supporting (approximately) 3,200 pounds per column. Figuring un-braced lengths in both axis, a 4x4 post should be adequate.

I would beef up the joists under the deck, possible by running additional joists between the existing at 12 centers. Transfer this load to the beams with a new built up mud board (deck edge above columns), and this should stiffen it up.

With the railings tying into the roof structure above, I would suspect they are pretty sturdy?
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Old 06-08-2012, 11:49 AM   #11
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Please Help With My Existing Deck


Quote:
Originally Posted by piper131 View Post
Yes, I said it correctly, the joist are PARALLEL to the house!!
This is the part that bothers me the most. All of the weight of that deck is resting on the two framing members at each end of the deck. All of that weight is then transfered to the connection points at either end of it. If this is truly the case then adding joist hangers won't do anything.
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Old 06-08-2012, 01:21 PM   #12
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Can you get a shot from under the deck looking up?
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Old 06-09-2012, 08:56 AM   #13
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Please Help With My Existing Deck


Quote:
Originally Posted by piper131 View Post
There are no double or triple 2x8 on this entire deck. there is no beam under the joist anywhere. Just the 3 4x4 post notch to have the 2x8 box set on them. The plan is to double up outside the band and install two built up 4x4/4x6 frames (to the patio below) 3 foot in (perpendicular to the house) from each. This is to bring the joist span to 10 ft between the frames, with a 3 ft cantilever on each end.

Also, anyone want to guess if anything was said about this deck in the home inspection?
So you are saying that there are no double 2x8 boards on the two 10' outer edges coming out from the house that the 16' floor joists nail to? also, how the deck connects to the brick along the house is very important. more pics would help us to offer advice from a visual standpoint. Thanks
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Old 06-09-2012, 09:46 AM   #14
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Please Help With My Existing Deck


Quote:
Originally Posted by hand drive View Post
So you are saying that there are no double 2x8 boards on the two 10' outer edges coming out from the house that the 16' floor joists nail to? also, how the deck connects to the brick along the house is very important. more pics would help us to offer advice from a visual standpoint. Thanks
Two concerns. You outlined the first with no outsie beam. The second and potentially real dangerous is the attachment issue.

I will bet that it is not tied into framing members and is just a party away from collapsing.

I would not use that deck until all issues have been addressed.

Personally, I think it needs to be torn down and properly built.
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Old 06-09-2012, 10:04 AM   #15
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Originally Posted by framer52 View Post
Two concerns. You outlined the first with no outsie beam. The second and potentially real dangerous is the attachment issue.

I will bet that it is not tied into framing members and is just a party away from collapsing.

I would not use that deck until all issues have been addressed.

Personally, I think it needs to be torn down and properly built.

I'm concerned that they simply bolted the deck to the brick facade with lead shields or something, if there are no double band members to support the floor system then what else did they not do when building the deck. The inspector must have looked at the deck and decided there was to much " fixing " to recommend...

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