Deck framing

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ming
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Joined: Thu Jun 21, 2018 8:57 pm

Deck framing

Post by ming » Fri Jun 22, 2018 7:23 pm

Hey Shannon,

I enjoyed very much watching your videos on how to build a deck. Thanks for sharing your acknowledge.

I am planning to build a deck that's 24' wide, 16' deep and the height is between 17" and 23". It will be a low deck. What's the recommendation for the number of posts/holes, sonotube size (8" or 10") and the size for the ledger, beam and joists (i.e. 2x8 or 2x10)? Do I need posts since it is a low deck?

Thanks, Ming
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DanM
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Re: Deck framing

Post by DanM » Fri Jun 22, 2018 8:39 pm

Well there's a few things to take into account, I'll break them down for you. One thing though, you always need to double check your local codes.

First, yes you need posts. You may be able to use deck blocks instead of actual poured concrete piers (deck blocks are just a concrete block that a 4x4 can sit in). However, for a deck that size I wouldn't recommend them. They move around a lot and your deck will get wonky over time. For your piers there are 2 options. You can do Sonotubes + concrete, or you can look into screw piles. Screw piles are basically a 4 foot metal screw with a saddle for a 4x4 (or 6x6) on top that you put into the ground. I absolutely love them since they're a million times less labour than digging holes, setting up sonotubes, and mixing a ton of concrete. It takes 10-15 minutes to put a screw pile into the ground. They're slightly more expensive than concrete but not much. For me it's about $22.50 per hole for concrete, and $28 for a screw pile (not including renting an auger to dig your holes for the sonotubes).

To support your beams you need posts at a maximum of 8 feet apart. So at 24'5" you could probably get away with 5 posts per beam, though you might need 6 if they're sticklers (Or you could shrink the deck to 24'). For your beams themselves double 2x10's would be fine.

For your joists there's a few things to consider. The maximum span for a 2x10 joist is just over 15' (depends on the species of wood and grade), 2x8 joist is about 12' maximum span. If you wanted to save on beams and posts, you could shrink your deck from 16'8" to 15' and use 2x10 joists. This way you'd only need one beam plus 5/6 posts. If you don't want to shrink the deck then you can use 2x8 joists but you'll need two beams + 10/12 posts. You'd have one set of 2x8 joists going from the house to the middle beam, and another set of joists going from the middle beam to the end beam.

ming
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Re: Deck framing

Post by ming » Fri Jun 22, 2018 9:44 pm

Hi DanM,

Thanks for your quick reply. I will shrink my deck size to 24' x 15'. If I use 2x10 for both the beam and joists, will it exceed the height of my deck since the deck height is between 17" and 23"? I will hire a contractor to do the concrete piers, should I use the 8" sonotube or 10"? What size should I use for the ledger?

Thanks, Ming

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A. Spruce
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Re: Deck framing

Post by A. Spruce » Fri Jun 22, 2018 9:58 pm

You don't have to have your support posts at the ends of your beams, you can cantilever them a bit, which means you don't have to shorten the deck to stay under 24'. IMHO, you can cantilever 1' to 2' without getting spongy on the tips of the beams. The only caveat is if you plan to put a hot tub/spa on the deck, then you've got to have enough support under that particular area to handle the weight of the spa. The amount of support you need will depend on the size of the spa.

Dan has a good point with the auger anchors over poured footings. So long as they're allowed in your area, I would seriously look at this option. The time and labor savings more than makes up for the slight increase of cost. If you have to rent equipment to dig your footing holes, that is even more argument for the auger anchors.
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DanM
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Re: Deck framing

Post by DanM » Sat Jun 23, 2018 9:25 am

ming wrote:
Fri Jun 22, 2018 9:44 pm
Hi DanM,

Thanks for your quick reply. I will shrink my deck size to 24' x 15'. If I use 2x10 for both the beam and joists, will it exceed the height of my deck since the deck height is between 17" and 23"? I will hire a contractor to do the concrete piers, should I use the 8" sonotube or 10"? What size should I use for the ledger?

Thanks, Ming
2x10's are 9 1/4" actual size (+/- 1/4"), so the beam plus joist would be about 18 1/2" total. Where it's around 17" I would just dig down the dirt a few inches to make sure you have enough room. You may not actually need posts if you get an adjustable saddle, you can just sit your beams in the saddles and adjust it until they're level.

Another option would be to have the 2 ply 2x10 beam sitting on 4x4 posts, and have the top of the beam at the same height as the top of the joists will be. All the joists will need to have joist hangers this way though, but those are like $1.50 apiece.

Your ledger board should be the same size as your joists, so 2x10.

Go with 8" Sonotubes if your posts will be 4x4, which is completely ok if you aren't planning on having a hot tub (or something else really heavy) or if you decide to sit your beam on adjustable saddles like I mentioned above. If you want 6x6 posts, which are probably overkill but stronger never hurts, go with 10" Sonotubes.

And like Spruce mentioned, if you're planning on having a hot tub let us know, you need waaaaaaay more support than usual if you want to support one. We can help you with that.

ming
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Re: Deck framing

Post by ming » Sun Jun 24, 2018 8:53 am

Hi DanM,

My concern with the 2x10 ledger board is that the top of the ledger would be attached to the brick and the bottom would be attached to the concrete foundation. Here is a picture. The green line indicates where I would like the top of the deck board to be. The yellow rectangle indicates the ledger board attachment to both the brick and the concrete.

Another concern is that the brick and the concrete are not flush as shown in the second picture. I guess I would need a piece of shim/spacer against the concrete to make it flush with the brick?

Thanks, Ming
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DanM
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Re: Deck framing

Post by DanM » Mon Jun 25, 2018 5:43 pm

I wouldn't use shims, you'd need some beefy spacers that could fit around the anchor bolts. A stack of stainless or galvanized steel washers, I know they make spacer 'pucks' that are teardrop shaped (those kinda control the way water flows) but for some reason they're really hard to find at shlomo depot or places like that.

As for anchor bolting, you want them in pairs usually every 16" or so. Just try to make them so they aren't where your joists will end up, saves you some pain later. For each pair you want one about 2" from the bottom of your ledger board, and the other one about two inches down from the top of the concrete (You can't anchor bolt into bricks). You also want a decent amount of vertical space between them, at least three inches IMHO. Hard to tell exactly from the picture but that may be an issue. If it is, then you could lower the height of your deck a little to give you enough space in the concrete to get your anchor bolts in.

ming
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Re: Deck framing

Post by ming » Tue Jun 26, 2018 8:26 pm

Hi DanM,

I am thinking about to make it free standing to avoid attaching the ledger board. Please see attached drawing. Do you think 10 posts is enough? There would be 2x10 joists sitting on top of the double 2x8 beams. Do you see any issues with this plan?

Thanks, Ming
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Shannon
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Re: Deck framing

Post by Shannon » Wed Jun 27, 2018 9:49 pm

Ya I think free standing in this case may be the best. Attaching to that wall will be a pain to do properly.
You could go with 24” cantilever from each end of the joists and I would also use 2x8x16’ joists which will shrink down the deck size to a max of 16’. Joists 24”o.c and a row of blocking down the center.
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ming
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Joined: Thu Jun 21, 2018 8:57 pm

Re: Deck framing

Post by ming » Fri Jun 29, 2018 4:58 pm

Hi Shannon,

Do I need flashing for free standing deck since there's no ledger board attached to the wall?
There a big gap when I put the double 2x8 beams on the bracket. Please see picture attached. Is it okay there's a gap? Do I need a spacer to fill it?

Thanks, Ming
Shannon wrote:
Wed Jun 27, 2018 9:49 pm
Ya I think free standing in this case may be the best. Attaching to that wall will be a pain to do properly.
You could go with 24” cantilever from each end of the joists and I would also use 2x8x16’ joists which will shrink down the deck size to a max of 16’. Joists 24”o.c and a row of blocking down the center.
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Shannon
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Re: Deck framing

Post by Shannon » Sat Jun 30, 2018 3:43 pm

No flashing needed.
The gap in the saddle is fine, you can just bolt the beam and bend saddle or place a small piece of 1/2” ply in there if you want so it does not bend.
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