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Discussion Starter · #1 ·
I'm looking to increase the size of my deck by about double (14' deep to 28'). My current deck has a metal shed constructed underneath it on a concrete slab which is the entire size of the deck. There are currently (4) 6x6 posts which are supporting the deck and which run through the inside of the shed. I would ideally like to keep the shed and pad for the shed as much in the same condition as possible, since it's just fine.

My calculations put the pier base size to be around 18" for the ones that will land inside of the shed. The new ones I put in will be outside of the shed and are really of no concern. I dug down on one of the corners outside of the shed (under the slab) to see what type of foundation is under there. Unfortunately, it looks like it's only about a 4" concrete pier about 42" deep with no base.

My question is this. Is there any way to utilize the existing columns and increase the size of the base in some way without disturbing the interior pad in the shed? The current piers are way undersized currently and are only going to be worse when I add on to the deck. Would it be possible to use a mini excavator or something to dig around the existing piers and add a footing to the bottom, or is this way more work than necessary? Just looking for some suggestions on the best way to approach it. Thanks!
 

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retired framer
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Does the deck extend passed the shed any, an inch or two?
 

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retired framer
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It's pretty much flush with the front.
Are you sure that it is concrete below the slab or just wood stuck in the ground.
I would leave it alone and just build the new deck with 2 beams 10 ft apart and just tie the joists into that decks rim joist.
 

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Discussion Starter · #5 ·
Are you sure that it is concrete below the slab or just wood stuck in the ground.
I would leave it alone and just build the new deck with 2 beams 10 ft apart and just tie the joists into that decks rim joist.
I'm sure, I dug all the way down and saw the 4" concrete pier 42" deep. I have no idea why anyone would pour a 4" pier, but that's definitely what it is on the corner anyway (I didn't dig every one of them out). My concern is, the deck is already 14' deep, so when I extend it to 28', the location of the current posts will basically be the middle of the deck and the load will be around double what it was before on those posts.

Also, just to be clear, I'm ripping off all of the old deck and starting new, I just wanted to reuse the posts if possible since they go through the shed.
 

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retired framer
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I'm sure, I dug all the way down and saw the 4" concrete pier 42" deep. I have no idea why anyone would pour a 4" pier, but that's definitely what it is on the corner anyway (I didn't dig every one of them out). My concern is, the deck is already 14' deep, so when I extend it to 28', the location of the current posts will basically be the middle of the deck and the load will be around double what it was before on those posts.

Also, just to be clear, I'm ripping off all of the old deck and starting new, I just wanted to reuse the posts if possible since they go through the shed.
Are the joists 2x8 now?
 

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retired framer
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It's not. They have a 6x6 inside the shed up to the roof, then attached it with a short metal piece on top. Basically they're sandwiched with the roof between.
What they did was pull out an old 4x4 and filled the hole with concrete.
 

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Discussion Starter · #13 ·
What they did was pull out an old 4x4 and filled the hole with concrete.
I had originally thought that too, but it's a perfectly poured pier, I'm assuming with a sonotube or form. Here are a couple of extra photos to better explain...

The problem is, if it were really shoddy work, I'd just say screw it and scrap it all, but the posts and piers are in really nice condition, they're just way too small.
 

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retired framer
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I had originally thought that too, but it's a perfectly poured pier, I'm assuming with a sonotube or form. Here are a couple of extra photos to better explain...

The problem is, if it were really shoddy work, I'd just say screw it and scrap it all, but the posts and piers are in really nice condition, they're just way too small.
But if it has passed the test over time you could just replace what you had and I will go back to my first suggestion.

654424
 

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Discussion Starter · #15 ·
But if it has passed the test over time you coud just replace what you had and I will go back to my first suggestion.
Okay, I see what you're saying. I guess the issue I have with putting in any new posts closer to the house (less than the current ones that are 14' out) is that they'll land right in the middle of the shed. The current ones are next to the outer wall which leaves the shed area pretty open in the middle. Otherwise I'm going to have a pretty unusable area. So, in short, I need the 14' (or so) clear span from the ledger board to the first set of posts.
 

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Okay, I see what you're saying. I guess the issue I have with putting in any new posts closer to the house (less than the current ones that are 14' out) is that they'll land right in the middle of the shed. The current ones are next to the outer wall which leaves the shed area pretty open in the middle. Otherwise I'm going to have a pretty unusable area. So, in short, I need the 14' (or so) clear span from the ledger board to the first set of posts.
No I am saying you rebuild that section just as it is now, if it has worked to now you are not adding any thing.
Then you just do another deck on the end and use the same rim joist for both.
 

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Discussion Starter · #17 ·
No I am saying you rebuild that section just as it is now, if it has worked to now you are not adding any thing.
Then you just do another deck on the end and use the same rim joist for both.
I see what you're saying, I don't think I explained it that well. I'm extending OUT from the house an additional 14 feet, not making the deck wider. So, basically I'm going to be lap joining another 14' joist on top of the current beam to extend out a total of 28' from the house (it's currently 14'). I'll be adding a second beam and 4-5 posts about 12' out from the current beam.
 

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retired framer
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I see what you're saying, I don't think I explained it that well. I'm extending OUT from the house an additional 14 feet, not making the deck wider. So, basically I'm going to be lap joining another 14' joist on top of the current beam to extend out a total of 28' from the house (it's currently 14'). I'll be adding a second beam and 4-5 posts about 12' out from the current beam.
Would it make more sense if I said to build the second 14 ft 0ne step down as a separate deck
654425
 

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Sorry, I see what you're saying. just adding another set of piers outside of the shed. I'm not sure why I didn't think of it that way, that probably makes a lot more sense.
New beams at 2 ft and 12 feet from the old rim board.
 
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