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 4×4 posts to support the deck. The beam underneath the deck comprises four 2x10s sitting on top of 4 6×6 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!
Best Answer
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.