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My deck has 12' joists and is 20' wide. It's attached to the house by ledger board. This is in Connecticut and house was built in 2013 to put into perspective the building code at the time. The builder specified four 4x4 posts to support the deck. The beam underneath the deck comprises four 2x10s sitting on top of 4 6x6 posts. We upgraded the 4x4s to 6x6s for added strength and for the look.

We are now looking to pour a concrete pad underneath and to do this we are going to be temporarily supporting the deck and removing the 6x6s.

I'm hoping you all feel if I remove the two center 6x6s the two outer 6x6s will be enough to handle the load of the deck, a gas grill (maybe 300 pounds) and of course family members.

The two outer most 6x6s that I'm hoping to leave are about 1 foot in from the edges of the quad beam

Is this enough? Can it be supported by those two 6x6s if I say upgrade the quad beam? Can I upgrade the 6x6s to leave the existing quad beam instead?

Thank you!!! Need to do this by Friday so I'm hoping some of you guys can respond today please!

https://photos.app.goo.gl/WdHUouE7qCbXhTM8A

Just added photos at the above link they were to large to add directly. The outside posts are only about 10" in.

Thank you!

  • Yes, some pics (edit your post, click the "sun & mountains" icon, browse your computer & it will upload/host the images for you) would be most helpful. A wider, overall shot or two, then some closer in detail shots of the areas you're looking to modify. Even better if you can edit them to include pointers to (or highlight) the beams you're planning on removing. I have to say, though, after a couple of re-reads, it sounds like you're planning on removing 2 of 4 6x6" posts leaving about an 18' span. I doubt that will work unless you have a steel beam spanning the gap. – FreeMan Jun 24 at 13:26
  • I don't think that even 4 2x10s will be enough to span the ~18' remaining between your two remaining posts. (If I'm reading you correctly.) Oh, and welcome to Home Improvement! After you've added some pics, please take the tour and browse through the help center to ensure you know how to get the best out of the site. – FreeMan Jun 24 at 13:28
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    Decks have, in general, very particular requirements because there have a lot of tragedies due to decks falling down. Temporary removal to work underneath is one thing. Permanent removal is an entirely different story and very much not recommended unless you get the local building department to sign off on it. Unlike so many other things (don't get me started) this is one case where the building codes really are about safety. – manassehkatz-Moving 2 Codidact Jun 24 at 13:43
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    Yeah, looking at those pics, you do NOT want to remove those two center posts! If you do really want to get rid of them, get with an engineer to have him design an LVL (Laminated Veneer Lumber), wooden I-beam, steel I-beam (or other structure that an engineer will sign off on) that will support the load. I'd expect you may have to beef up the 2 remaining posts, as well. You're probably looking at $$$ (probably not $$$$$, but certainly not $). – FreeMan Jun 24 at 16:01
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    To be honest, I wouldn't think that the toe-nailing that's holding that beam to the top of the posts to meet code requirements either. You're smart enough to think before you took on this project, be smart enough to take @manassehkatz-Moving2Codidact's advice and think about safety! You should seriously look at the post-to-beam connectors that are available and add additional security to the top of each one of those posts! – FreeMan Jun 24 at 16:05
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Temporary post removal

If the beam members don't all join over one post, you can probably temporarily remove the two interior posts while you do your concrete work. Assuming adequate lap (with no more than one butt joint over each post) and adequate cross-fastening (say three screws every 18"), it'll hold the empty deck for a span of 18'. If you see substantial pressure or movement when you remove the first post, consider temporary posts to the ground outside the concrete pour area.

You'll want to block off the entrance to the deck to make sure no one enters it during this time.

Permanent post removal

Generally speaking, the footings that would've been built in 2013 should be able to carry half the deck and its contents. Should. Without knowing what they are, we're speculating. 6x6 posts are also probably adequate, depending on specific local code. That leaves the question of the beam.

You'll need steel (or an outdoor-rated engineered wood beam), and you'll need an engineer to sign off on a size. Other than the challenge of moving such a beastly beam, it's more or less a drop-in situation. Ask your inspection office what type of fastening to the posts and joists they'd expect.

On the subject of beam connectors

I've never heard of a deck falling due to post or beam displacement, though I can imagine it happening in a severe wind situation or if someone hits one with a tractor. Having built dozens of decks through the 80s and 90s and beyond, we never used structural steel for that. Just toenailed screws. If you want to add something, go ahead, but I wouldn't worry about it.

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  • As a note, the posts are toe nailed to the beams, not toe screwed. – FreeMan Jun 24 at 17:03

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