[Pie]

Hi all,

I'm new here so I apologize if I'm asking something already covered.

I need to build a 15 x 40 freestanding deck which is not normally a problem. However the decking on one end will only be about 10" above grade not allowing room for my usual 2 x 8 joists and 2 x 8 beams. The only solution I can think of is to use internal beams (2-2 x 8s) set atop or into notched 6 x 6 posts and hang the joists from both sides of the beam with joist hangers. But I think I recall reading in the IRC that joists can only be framed from one side of a beam.

I'm sure this is a common situation but just one I've never encountered. Any suggestions?

Oh one more - anyone know where I can find the regs on using above grade blocks (DekBlocks or similar) for post footings? This is for an idea I have for a 36" wide deck encircling a pool. But with about a dozen 6' sections that's just too many holes to dig!!

Thanks everyone in advance.

 

[KennMacMoragh]

It's pretty common to hang joists on a beam like you described, the last deck I built was like that. What exactly did you find in the IRC that questions it? Another thing to keep in mind is if the deck is detached and it's that low, your city probably won't require permits, I know they wouldn't be required around here. Doesn't mean you can cheap out on the design but you won't have to comply with the IRC.

 

[Pie]

I just looked at it. It's called Design for Code Acceptance (dca-6) and it's BASED on the 2009 IRC. I guess that's the key word here. Since I'm not real savvy at navigating the Code this has been quite helpful, but now I'm wondering if it's misleading. I've seen a lot of decks built this way and wondered about them, but I've stuck with the post-beam-joist method because it allows for cantilevering and fewer posts. But by the same token I guess it's possible here too.

 

[KennMacMoragh]

If I saw the exact wording and the section it was in, I might know what it's talking about. But I'm not sure what you're looking at. If your deck is that low be sure to grade, slope the dirt under the deck, and put plastic over it. Otherwise your decking will rot pretty fast.

 

[ScipioAfricanus]

This is what he is talking about.

I have designed a few decks using this as a guide here in CA.

Andy.

 

[Pie]

If I saw the exact wording and the section it was in, I might know what it's talking about. But I'm not sure what you're looking at. If your deck is that low be sure to grade, slope the dirt under the deck, and put plastic over it. Otherwise your decking will rot pretty fast.

I copied this from the publication:

"BEAM SIZE & ASSEMBLY REQUIREMENTS
Deck beam spans shall be in accordance with Table 3 and can extend past the post centerline up to LB/4 as shown in Figure 3. Joists may bear on the beam and extend past the beam centerline up to LJ/4 as shown in Figures 1A and 2, or the joists may attach to the side of the beam with joist hangers as shown in Figure 1B.
Joists shall not frame in from opposite sides of the same beam. See JOIST-TO-BEAM CONNECTION details, Figure 6."

Thanks for the tip on the plastic. It had never crossed my mind.

 

[Pie]

Another thing to keep in mind is if the deck is detached and it's that low, your city probably won't require permits

The high end will be about 36" above grade. Anything above 30" requires one here.

 

[Calidecks]

The high end will be about 36" above grade. Anything above 30" requires one here.

Raise the grade

 

[CarpenterSFO]

I copied this from the publication:

"BEAM SIZE & ASSEMBLY REQUIREMENTS
Deck beam spans shall be in accordance with Table 3 and can extend past the post centerline up to LB/4 as shown in Figure 3. Joists may bear on the beam and extend past the beam centerline up to LJ/4 as shown in Figures 1A and 2, or the joists may attach to the side of the beam with joist hangers as shown in Figure 1B.
Joists shall not frame in from opposite sides of the same beam. See JOIST-TO-BEAM CONNECTION details, Figure 6."

Thanks for the tip on the plastic. It had never crossed my mind.

The language about the opposite sides doesn't mean that the detail isn't code-complying, only that the guide, which you can think of as the quick-start manual to designing a deck, doesn't cover decks with that detail. The next step up is your state's full residential code, then the building code.

 

[hdavis]

Raise the grade

I'd be looking at that too in this situation. Besides any permitting benefits, it gives more flexibility on guards.

 

[Golden view]

But I think I recall reading in the IRC that joists can only be framed from one side of a beam.

No, just the span table is for one side only. With joists on both sides the load is doubled. It's mentioned in the guide section c4.

You can still use the beam span table. just add the spans on each side of the beam together, and it works as long as they add to 18' or less.

 

[CarpenterSFO]

The language about the opposite sides doesn't mean that the detail isn't code-complying, only that the guide, which you can think of as the quick-start manual to designing a deck, doesn't cover decks with that detail. The next step up is your state's full residential code, then the building code.

Disregard my prior post, which was wrong. As Golden View points out, Section C4 covers it.

 

[tjbnwi]

The AWC deck guide lines are a perspective, not a code or part of the code except where highlighted in the perspective.

Tom

 

[Pie]

Awesome thanks guys. I don't have the actual book (I need to just bite the bullet and get it) but I look it up from time to time on publicecodes.com. I've never had any luck finding a section on decks - just flooring. That's why I was relying so heavily on the AWC guide.

 

[Calidecks]

Awesome thanks guys. I don't have the actual book (I need to just bite the bullet and get it) but I look it up from time to time on publicecodes.com. I've never had any luck finding a section on decks - just flooring. That's why I was relying so heavily on the AWC guide.

It's in the "Means of Egress" section of the code book.