Another ledger question


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Old 05-26-12, 12:45 AM
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Another ledger question

Long story, but I hope that someone out there can help me.

Basics:

Full brick walkout ranch, built in 1962
Current deck is 8 x 20

We're rebuilding the deck off of our first floor at the back of the house, making it a 10 x 20. The deck is elevated 8 feet off of the back poured concrete patio, which has a triple-pane slider into the basement (just like on the first floor).

The old deck was a cantilevered job with some puny 4x4 posts that really didn't take much of a load; the deck joists were sistered to joists that I assume were bolted to the house joists inside (can't tell b/c we have a finished basement). As you can imagine, the older joists (those coming out of the house) are rotting at the ends.

So I decided to replace our deck with a freestanding one. I'm going with 5 6x6 posts, three on the ends (double 2x10 beam) and two closest to the house b/c of the sliding door preventing a three-post setup (will be using a 2x10 triple beam to support the additional span).

My problem is in trying to figure out how to attach a ledger to the house, to give the deck greater lateral strength (since the deck is freestanding). The county inspector recommended that I drill several holes into the mortar and lag bolt the ledger to the house's band joist. After reading up on that (and reading the IRC), I don't think that's a good idea, because of the load that long bolts will transfer through the 3" brick and 1" of air gap.

However, the existing sistered joists will be cut flush with the brick, and would provide a decent anchor point for those lag bolts. Now I'd never do this to attach a traditional load-bearing ledger, but considering that the primary vertical load will be carried by the 6x6 posts, would this be ok if I'm just using the ledger for lateral support?

And yes, I'm going to make doubly sure the joist gaps in the brick are recaulked well. Water isn't much of a problem close to the house, since we have a nice, big hip-roof overhang.

Thanks all.
 
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Old 05-28-12, 05:02 PM
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A freestanding deck doesn't need a ledger. If it has a ledger, it's not freestanding. A true freestanding deck can be built in the middle of a field, with nothing around it. If you want a little extra support a couple 4 inch L brackets are all you need.
 
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Old 05-30-12, 04:45 PM
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Shame on your county inspector for not being familiar with the IRC for decks. You should print out Page 12, Figure 17 of the Code and take it in to show him the wording: "No Attachment To or Through Exterior Veneers (Brick, Masonry, Stone)." If he insists on sticking to his recommendation of drilling through your bricks, get something in writing from him or his boss, with an explanation of why they don't want to comply with the Code. It will cover your butt (and possibly save you some serious corrective costs) should new county building people be on board come time to sell your house, and the buyer's home inspector points out the non-compliant ledger attachment.

The earlier suggestion to use 4" L brackets to stiffen things up is not a good one--doing so will result in a wobbly deck, and is also in contradiction to the IRC. For free-standing decks, Figure 22 on Page 14 requires diagonal 2 x 4 top corner braces at 45 degrees, with 2' offsets, between your beams/joists and columns. Also, your triple 2 x 10 beam nearest the house may be slightly overstressed--the IRC only allows a maximum span of 12'-0" for most species of softwood, 14'-5" for Southern Pine. Based on your beam clear span being close to 16', cantilevered 2' at each end of the total 20' length you mentioned earlier. You'll be happier (and your deck will be stiffer) going with a triple 2 x 12 beam. Either that, or add a third column, offsetting it to clear the sliding door.
 
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Old 05-30-12, 07:12 PM
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Why would the 4" L brackets cause the deck to be wobbly when a free standing deck shouldn't need that or any support attached to the house? As I said, a free standing deck can be built in the middle of an opened field. That came from an architect I have worked with on a number of projects.
 
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Old 05-30-12, 09:08 PM
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Bridgeman75, I'm not spanning the entire 20 feet with the triple 2 x 10. The span will be 12' 10", as indicated in the code book. The amount of cantilever can be Lb/4, which in this case would mean the proper cantilever would be 3'2.5" My cantilever would only be a few inches more than that, or no more than 4'. The inspector also said that two posts spaced on either side of my 9'+ patio door would be ok. I'm going to use 4x4 outside diagonal braces on that particular beam to help prevent any swaying on either end.

I'm not attaching the deck to the house through brick, but could I use the end grain of the 2 x 12's coming out of the house (none of the existing deck was attached to the brick veneer) to put in a few lag bolts to help give the deck even more lateral stability? I'd never use the end grain to hold lag bolts if it were holding the primary load, but since this is a freestanding deck I don't see a big issue, and leaving an half-inch joist stub would create a gap that could help with water drainage (although we have a considerable overhang). And yes, I would be making sure to flash the joist stub ends coming out of the house.

Here's what it looks like after demo.

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Old 05-30-12, 10:25 PM
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It's your money and risk should you choose to build a deck that doesn't comply with the IRC. I know I wouldn't, but then I've always preferred to build things that aren't a liability come time to sell the property. Any reasonably sharp home inspector your buyer hires down the road will point out any deck deficiencies you build into it, causing the buyer to either walk or whittle down your asking price by a chunk of $$$ to pay for the corrections necessary to make the deck Code-compliant. And one more thing--building close to 4' cantilevers as you described is asking for trouble, with the diagonals wanting to kick out the rim joists when loaded with a large party of heavy people.

Pulpo, maybe you (or your architect) could show us which part of the IRC allows 4" L-brackets for stiffening a free-standing deck. Can't seem to find them in my copy of the Code. Such brackets are not at all structural, made out of thin stamped steel that can be easily flattened by stepping on them. I've already referenced the IRC stiffening requirements (diagonal braces) needed to make free-standing decks Code-compliant--with the key Code words being "Decks greater than 2' above grade shall be provided with diagonal bracing."

FWIW--Architects are far better at making things look pretty than providing sound engineering advice.
 
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Old 05-31-12, 03:12 AM
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Thinking outloud, with only one cup down. If the original deck caused no structural problems being cantilevered through the veneer, could you not use inverted joist hangers (with slight chiseled out gaps on the 2x12's) to mount a ledger, using posts on either end for radial support of the remaining deck with sub framing to match the cantilever for decking support. I don't think the IRC has seen this set up. It wouldn't make it free standing, but you gotta do something with those cantilevered stubs. Really can't understand why someone would design in cantilevered decking on a house, knowing in 10 or 12 years it will fail due to moisture problems.
 
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Old 05-31-12, 10:23 AM
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Bridgeman45, I don't know about that code but the my architect knew codes inside & out. He was always quoting codes to me. The deck is no longer free standing if there is any attachment to the house so why would the code call for it? I don't know how anyone could step on the L brackets either.
 
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Old 05-31-12, 01:16 PM
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Chandler, going your route is certainly feasible, and possibly wouldn't even need end support posts to meet the IRC requirements (Figure 23, "Attachment of Free-standing Deck to House for Stability"). Sounds like the OP's county inspection department would probably buy into it too.

Pulpo, how about calling your architect and getting a Code reference number that he uses to justify L-brackets for free-standing deck stability? It would be good to know if there's a legal alternative out there. And also, the IRC code defines a free-standing deck as any that does not use the exterior house wall to support vertical deck loads, even though it may be attached per the reference in the paragraph above.
 
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Old 05-31-12, 04:04 PM
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I really don't want to bother the guy for that. He is very busy & would always complain about losing time. I trust your interpretation of the code. The L brackets came up when I was building a second story deck according to his plans. He told me that I could use the L brackets because I was a little nervous about having nothing there at all. However, he was the one who told me that a freestanding deck can be build in the middle of a desert without fear of it falling.
 
 

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