Decks and IRC

[Richard Moore]

Jim,

I'm looking through the MASER document. I have a concern with this:

9.

Decking must have a span length such that each

board bears ona minimum of two joists.

Really? Span to 2 entire joists? Are they meaning that with say 16" o.c. framing that you only have to have a 16" surface board?

I've always thought at a bare min. you should span to 3 joists

That has to be wrong. In the "Prescriptive Residential Deck Construction Guide" put out by www.awc.org that Chris posted earlier, is the following..."Each segment of decking must bear on a minimum of 4 joists."

That makes sense as even 3 could pose a problem. Imagine end rot where the deck board is about to fail at its 3/4" bearing on the joist. With just a little rot at the other end of the deck board I could see the nails or screws failing there and the center joist simply acting as a fulcrum as the unlucky homeowner puts his foot through the deck. At least with 4 joists you stand a good chance of the middle of the board still being good wood and the middle two joists providing enough resistance to prevent complete failure. Hopefully, the homeowner would notice the springiness and take corrective action before his nuts meet the deck.

[Jim Katen]

Jim,

I'm looking through the MASER document. I have a concern with this:

9.

Decking must have a span length such that each

board bears ona minimum of two joists.

Really? Span to 2 entire joists? Are they meaning that with say 16" o.c. framing that you only have to have a 16" surface board?

I've always thought at a bare min. you should span to 3 joists

I raised my eyebrows at that as well. Presumably that's what they mean though.

Also,

I think you left out key word here:

* Section R403.1.4.1 says that foundations, piers, and other building supports hqave to be protected from frost. . . except for decks that are

not

supported by a dwelling -- they don't need footings that extend below the frost line.

Bold added where I think you left out a word.

Yes, you're right.

Here's the actual wording:

Decks not supported by a dwelling need

not be provided with footings that extend

below the frost line.

- Jim Katen, Oregon

[Brandon Whitmore]

Oops, bold was not added after all. I should start reading my posts after I hit send. [:-paperba

[FrankWoeste]

Am I blind, or is there any deck reference in the 2006 IRC?

Kurt:

I realize your question cites the 2006 IRC. If you are still looking for ledger connection design data that is ready for adoption by states and jurisdictions, you can find a table in the 2009 IRC, page 113. The table caption is:

TABLE R502.2.2.1

FASTENER SPACING FOR A SOUTHERN PINE OR HEM-FIR DECK LEDGER AND A 2-INCH NOMINAL SOLID-SAWN SPRUCE-PINE-FIR BAND JOISTc, f, g

If you are interested in ledger connection design data for connecting to Engineered Wood Product (EWP) rim boards, you can find that data in Table 5 at:

http://awc.org/Publications/DCA/DCA6/DCA6.pdf

Frank Woeste

Professor Emeritus

Virginia Tech University

Blacksburg

[kurt]

Thank you Frank. Direct links and cites are a wonderful thing........

[Bain]

The deck portion of the code is still woefully inadequate. I have a builder who's claiming that roofing felt is perfectly acceptable between a house and a deck.

There's nothing in the code that says the flashing has to be metal; the IRC and our state code merely say approved flashing or non-corrosive flashing shall be installed.

[kurt]

I know; it's painfully thin.

I was just extending a welcoming hand to Professor Woeste........

http://www.cnr.vt.edu/wood/htdocs/vtwoo ... ?newsID=37

[Chad Fabry]

There's nothing in the code that says the flashing has to be metal; the IRC and our state code merely say approved flashing or non-corrosive flashing shall be installed.

I don't have my books at home but I think it's R703.8?

On this topic... should we have a category for interpretation? Maybe we could call it "Speaking in Code"?

[kurt]

On this topic... should we have a category for interpretation? Maybe we could call it "Speaking in Code"?

I like the name.

Don't know if we need a separate conference for it. I like the idea though.

[Bain]

There's nothing in the code that says the flashing has to be metal; the IRC and our state code merely say approved flashing or non-corrosive flashing shall be installed.

I don't have my books at home but I think it's R703.8?

On this topic... should we have a category for interpretation? Maybe we could call it "Speaking in Code"?

Our state code's R703.8: Approved corrosion-resistive flashing shall be provided in the exterior wall envelope in such a manner as to prevent entry of water . . .

Silly-Putty pretty much fits the bill except for the "approved" part of the citation. The problem around here, though, is none of the local enforcement people want to take a stand and say what is or isn't approved.

[Bain]

I know; it's painfully thin.

I was just extending a welcoming hand to Professor Woeste........

http://www.cnr.vt.edu/wood/htdocs/vtwoo ... ?newsID=37

No disrespect toward Professor Woeste. Welcome aboard.

[FrankWoeste]

Bain and Kurt:

Thank you for the warm welcome to the discussion. Attached is a research report that combined the PPT Southern Pine ledger testing results with the PPT Hem-Fir ledger testing results. It was interesting to learn that 1/2" thru bolts were about twice as strong as 1/2" lag screws in this application (ledger connected to SPF house band without stacked washers).

Download Attachment: WDF Deck Ledgers Aug. 2006.pdf

372.43 KB

Frank

[Terence McCann]

Bain and Kurt:

Thank you for the warm welcome to the discussion. Attached is a research report that combined the PPT Southern Pine ledger testing results with the PPT Hem-Fir ledger testing results. It was interesting to learn that 1/2" thru bolts were about twice as strong as 1/2" lag screws in this application (ledger connected to SPF house band without stacked washers).

Download Attachment: WDF Deck Ledgers Aug. 2006.pdf

372.43 KB

Frank

It's great to have you here Frank, welcome.

Misinformation about deck construction abounds. Perhaps you can talk about the importance of the ledger board attachment to the home. What is the correct way to attach the ledger board to the home?

[Kyle Kubs]

There's nothing in the code that says the flashing has to be metal; the IRC and our state code merely say approved flashing or non-corrosive flashing shall be installed.

I don't have my books at home but I think it's R703.8?

On this topic... should we have a category for interpretation? Maybe we could call it "Speaking in Code"?

Our state code's R703.8: Approved corrosion-resistive flashing shall be provided in the exterior wall envelope in such a manner as to prevent entry of water . . .

Silly-Putty pretty much fits the bill except for the "approved" part of the citation. The problem around here, though, is none of the local enforcement people want to take a stand and say what is or isn't approved.

There is something more specific about what approved flashing is or is not. My head is swimming with several other things right now but I'll look for it. Often I find this type of supporting information not in the codes but in things like ASTM standards. As far as the felt goes that is pretty easy, the manufacturers specs list a limit of exposure to UV light... Never a shortage of dumb asses among builders.

[FrankWoeste]

Misinformation about deck construction abounds. Perhaps you can talk about the importance of the ledger board attachment to the home. What is the correct way to attach the ledger board to the home?

Terry:

I suggest you take a look at Figure 14, page 11 of this document for connection to a solid-sawn house band bearing on a sill plate:

http://awc.org/Publications/DCA/DCA6/DCA6.pdf

DCA6 is a wood industry document.

Frank

[Bain]

There's nothing in the code that says the flashing has to be metal; the IRC and our state code merely say approved flashing or non-corrosive flashing shall be installed.

I don't have my books at home but I think it's R703.8?

On this topic... should we have a category for interpretation? Maybe we could call it "Speaking in Code"?

Our state code's R703.8: Approved corrosion-resistive flashing shall be provided in the exterior wall envelope in such a manner as to prevent entry of water . . .

Silly-Putty pretty much fits the bill except for the "approved" part of the citation. The problem around here, though, is none of the local enforcement people want to take a stand and say what is or isn't approved.

There is something more specific about what approved flashing is or is not. My head is swimming with several other things right now but I'll look for it. Often I find this type of supporting information not in the codes but in things like ASTM standards. As far as the felt goes that is pretty easy, the manufacturers specs list a limit of exposure to UV light... Never a shortage of dumb asses among builders.

Thanks, Kyle, that will help in the future. This builder's been around a while and knows better. The subs screwed up and he simply doesn't want to admit it and incur the cost of flashing the deck correctly.

[RobC]

Often time it's not always about codes.

I rely on this documentation for evaluating ledgers.

http://www.apawood.org/pdfs/managed/W34 ... N=70285302

The Canadian version:

http://www.apawood.org/pdfs/managed/D34 ... N=70285302

Check out page three.

My favorite page.

http://www.apawood.org/level_b.cfm?cont ... _prog_main

[Jim Katen]

Bain and Kurt:

Thank you for the warm welcome to the discussion. Attached is a research report that combined the PPT Southern Pine ledger testing results with the PPT Hem-Fir ledger testing results. It was interesting to learn that 1/2" thru bolts were about twice as strong as 1/2" lag screws in this application (ledger connected to SPF house band without stacked washers).

Download Attachment: WDF Deck Ledgers Aug. 2006.pdf

372.43 KB

Frank

Hi Frank,

It makes sense that the through bolts would make a substantially stronger connection. But at what point does that strength become moot? I suspect that long before the bolted ledger-to-rim joist connection would fail, you'd see a failure of the connection between the deck joists and the ledger.

Is there any point to making the ledger connection to the house stronger than the ledger connection to the deck joists?

Isn't it kind of like trying to make a chain stronger by making one of its links *really* big?

- Jim Katen, Oregon

[Kyle Kubs]

Bain and Kurt:

Thank you for the warm welcome to the discussion. Attached is a research report that combined the PPT Southern Pine ledger testing results with the PPT Hem-Fir ledger testing results. It was interesting to learn that 1/2" thru bolts were about twice as strong as 1/2" lag screws in this application (ledger connected to SPF house band without stacked washers).

Download Attachment: WDF Deck Ledgers Aug. 2006.pdf

372.43 KB

Frank

Hi Frank,

It makes sense that the through bolts would make a substantially stronger connection. But at what point does that strength become moot? I suspect that long before the bolted ledger-to-rim joist connection would fail, you'd see a failure of the connection between the deck joists and the ledger.

Is there any point to making the ledger connection to the house stronger than the ledger connection to the deck joists?

Isn't it kind of like trying to make a chain stronger by making one of its links *really* big?

- Jim Katen, Oregon

Not that it should matter in a perfect world where the whole thing is done right, but I think when you have poor or no flashing the lags will be more prone to letting go.You only need to rot the wood directly around the lag threads. With the through bolts it has to get to the point where the entire rim joist will let go or is rotted out sufficiently to let the entire washer come through it.

[hmiller]

This deck collapse story seems fitting for this topic....http://www.king5.com/localnews/stories/NW_062209WAB-orting-deck-collapse-SW.175177de.html

[kurt]

Is there any point to making the ledger connection to the house stronger than the ledger connection to the deck joists?

- Jim Katen, Oregon

I'd like to hear Franks answer, but in the meantime.......

I had it explained to me as the loads on the joist/ledger connection are spread out over several connecting points by the floorboards, brackets, reinforcement, and the large number of connecting points. There isn't any one joist/ledger connection that's point loaded (unless someone is parking a car on the deck).

The ledger, otoh, is taking all those loads and transferring them to a few bolt connections to the house. The loads are not spread among several members. The ledger connection fails first.

From my reading, it seems like ledger connections are the most common point of deck failure. After ledgers, it's usually a vertical support inadequacy, usually when the deck is partially cantilevered and supported by girders angled back into the house wall.

I don't think I've ever heard of a deck failure involving the joist/ledger connections.

[Jim Katen]

. . . I don't think I've ever heard of a deck failure involving the joist/ledger connections.

I might be mis-remembering, but I though that Chuck B. posted one a few years ago. The joists has pulled clean off of the ledger.

- Jim Katen, Oregon

[Jim Morrison]

Here's one:

I saw a reasonably well constructed 10 x 14 deck that was only nailed into the house. The deck and ledger were pulled out 1/2 " or so from the house because the had been tethering their 100+ lb. Rottweiler to the deck, -and from the look of things- he wasn't the gentle sort.

I'm not saying we need to build decks to accomodate the unforeseeable; but applied against the standard of requiring AFCI's, I think lagbolting ledgers makes good sense.

[Brandon Whitmore]

As I recall, Charlie said that when he found failed decks, the ledgers had pulled away from the houses, leaving lags or bolts "sticking out like studs on a dog collar."

Hi WJ.

I wrote up the lack of bolts on a deck ledger a while back. For the re- inspection I went into the crawlspace to see if I could see any of the bolts (cripple wall). Every nice new shiny bolt end was visible in the sheathing between the studs. I see this quite often when the interior section of wall is exposed-- scary stuff.

[hausdok]

Some years back, Charlie Wood was working a lot of building-defect cases, several involving failed decks. As I recall, Charlie said that when he found failed decks, the ledgers had pulled away from the houses, leaving lags or bolts "sticking out like studs on a dog collar."

The visual has stuck with me since then.

WJ

Yeah,

Sometimes, they'll line up the bolt holes in a perfectly straight line and sock home those lags and washers like they're trying to split the ledger down the center. I can easily imagine a ledger splitting lengthwise and the deck and bottom half of the ledger going for a ride leaving the bolts and top half there.

ONE TEAM - ONE FIGHT!!!

Mike