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I want to build a flat ground level deck approx 25x26ft. I have very limited space between the ground and the door, so it needs to be streamlined.

I plan to use 3 26’ 2x10 as primary frame supports and than use 12’ 2x10 as joists with 12” spacing. Wondering how many posts do I need for each 26’ piece of lumber? Will 4 posts for each 26’ (6-1/2 apart) be enough? Also, will 12’ span for joists cause any issue? my plan

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    Your 2x10's seem to be undersized. I used doubled up 2x12's for a similar deck (enclosed with a roof), with the length being 16'. I had 3 posts supporting each beam.
    – SteveSh
    Apr 27 at 1:17
  • And did you look at some of the deck building guides out there?
    – SteveSh
    Apr 27 at 1:23
  • Seems like you're going to a lot of bother & expense to build a wooden patio, if vertical space is so tight.
    – Ecnerwal
    Apr 27 at 1:36
  • When you say "three 2x10s" do you mean tripled beams or three in total? A single 2x10 isn't adequate as a beam for spans over about 4'. Also, 26' 2x10s aren't a thing in most of the world. You need to plan for shorter beam member splices over posts.
    – isherwood
    Apr 27 at 16:18
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    You need six 26' long 2x10s, because beams need to be doubled. And it's two 12' spans, so you need a beam (and posts) in the middle. According to the link below, (in Maryland) you need a post every 7'4" when using 2x10s with a span of 12' or less. - A 12' span using 2x10s on 12" centers can be 16'2", so you're fine (16" OC can be 14'). - Using a single two-by member for a beam isn't even on the chart, and for good reason. - That all being said, I use 2x12s no matter what, and don't go further than 5', especially if doing a post every 4' can be my guard railing posts. 12 posts.
    – Mazura
    Apr 28 at 3:37

2 Answers 2

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It looks like the posts you show in your drawing are 2' back from each end. That makes your actual span 22'. Using 1 post between these for an 11' span with a "beam" of 3-2 x 10's might work, but I would prefer to add 2 posts between your shown ones making each span about 7'4.

The 12' span for your joists (actually a bit less because of the center 3-2x10's- assuming you are hanging into those ?) is OK for a simple deck with no roof load and only the weight of the decking (and the 40 people dancing on it at your next party).

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  • 7'4" is the exact maximum called for in the Maryland link, +1. ... Also, cantilevered (+2) might bring it from needing three and a half posts (so, four) to just three. Or four instead of five... w/e the math says.
    – Mazura
    Apr 28 at 3:42
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The minimum number of posts will depend on very specific requirements. In my area, and I assume many others, the local building department can provide very detailed guidelines. Decks are a big deal due to safety concerns. Your local jurisdiction may simply refer to other sources (e.g., International Residential Code) but they may have very specific requirements which you will need to follow in order to get your deck approved.

However, in many areas there is an alternative, a floating deck. This is different from a traditional deck in a few key ways:

  • The posts sit on specially designed concrete blocks instead of being permanently attached to concrete footings. Actually, depending on the height of the deck, you may even have some of the frame resting directly on those blocks without posts at all. This eliminates the usual digging, concrete pouring, etc. and turns a deck into a truly DIY project.
  • The deck is not attached to the house. That is the exact opposite of a traditional deck where not only is the deck attached to the house, but it has to be attached in very specific ways to ensure safety.
  • The deck is height-limited compared to a traditional deck. But assuming "ground level" means "no part of the deck surface is more than a few feet above the ground", you're fine.
  • No permits required, depending on the jurisdiction and the size of the deck. In my area, your deck is big enough that a permit would be required, but the permitting and inspection process should be simpler than with a traditional deck.

This is one example deck block from Home Depot:

deck block

The middle fits 4x4 posts, the slots fit 2x lumber.

Super-easy. Only tools you'll need are a circular saw to cut the lumber and drill/drivers to screw everything together.

In a quick search, recommendations seem to be on the order of a deck block (which may or may not have an actual post in it) every 4 to 6 feet. That is more than a traditional deck, but the posts here are easy and inexpensive compared to a traditional deck.

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  • OTOH, some jurisdictions (like mine) won't allow a floating deck. :(
    – FreeMan
    Apr 27 at 13:00
  • @FreeMan, are you sure about that? You can't build a patio deck in the middle of your yard? That would be very odd.
    – isherwood
    Apr 27 at 16:17
  • They wouldn't allow one next to the house. Maybe in the middle of the yard they'd be OK with it.
    – FreeMan
    Apr 27 at 16:18
  • This doesn't answer the question. The only attempt do do so at the end isn't really an answer.
    – isherwood
    Apr 27 at 16:23
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    The major drawback to this plan is that it's difficult to keep the blocks level, especially in any freezing environment. As soon as one settles you have a wavy deck. I wouldn't do it unless cost and effort were at a premium.
    – isherwood
    Apr 27 at 16:30

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