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-   -   Deck Building Question - Installing Ledger Board to Rim Joists (http://www.diychatroom.com/f2/deck-building-question-installing-ledger-board-rim-joists-20634/)

Ler0y Jenkins 05-05-2008 08:45 AM

Deck Building Question - Installing Ledger Board to Rim Joists
 
1 Attachment(s)
I'm about to begin the process of building my own deck. The overall dimensions will be approximately 32' long by 12' wide. I've attached a picture of my plans for reference:

http://www.diychatroom.com/attachmen...2&d=1209991080

My question has to do with attaching the ledger board to the rim joist. My house is brand-new and like many new houses, it uses the engineered I-Joists mounted to an engineered rim joist. I'm not that familiar with this type of a set up so I'm a little confused. The last deck I built (with a friend) was mounted directly to a standard header joist, made out of 2"x12" (or whatever). The rim joist in my house is made by Timberstran and says "1.25"" Rim Joist E3" on it.

My friend advised me that I would not be able to mount the ledger directly to this rim joist because it does not have the structural integrity of a standard piece of wood. Also, he said that the rim joist is only secured to the I-joist on the flanges by two nails so it doesn't take a lot of lateral force to cause the rim joist to pull out from the I-joists. I was advised that I would have to use something called "blocking" to reinforce the rim joist.

I went over my neighbor's house (who recently built a deck on his house) to see what was done to reinforce the rim joist. Basically, he just cut what looked like a 2"x10" or 2"x8" into squares that fit up against the rim joist (from the inside of the basement) and in between each I-joist. He then nailed that to the rim joist and used lag bolts (not through-bolts) to the mount the ledger through the rim board and into the pieces of 2"x10" or 2"x8".

I really don't understand what structural value that has other than it prevents the lag bolts from ripping out through the rim joist. Why wouldn't through-bolts with big washers accomplish the same thing? Also, it doesn't seem to address the issue of the deck causing the rim joist to pull away from the I-joists??

In any case, as an alternative, I'm looking into using a product called "DeckLok Brackets." These are basically reinforced L-Brackets that connect to the I-joists and the rim joist. They basically transfer the weight of the deck from the rim joist to the I-joist. Here's a link to their website: http://www.deck-lok.com/install.htm.

And here's a picture of how they are applied to engineered I-joists:

http://www.deck-lok.com/images/ijoist-anim.gif

They are fairly pricey at about $10.00 a piece but I like the idea better than the blocking board idea. My question is, how many of these would I need for a 32' ledger board? My I-joists (inside the house) are spaced 20" apart. Would I be able to put one DeckLok Bracket (as opposed to a pair) on every other I-joist so that there would be one bracket every 40"?? Or, would I be better off using a pair every third I-joist so that there would be a pair of brackets (attached to either side of a single I-joist) every 60"?? Or could I get away with using a pair of brackets (attached to each side of a single I-joist) every fourth I-Joist so that there would be 80" in between each bracket?

Thanks in advance for the input.

mikey48 05-05-2008 10:29 AM

I see very little strength pulling side ways on these I-joists. I would contact the MFR of the joists and ask them.

Termite 05-05-2008 12:27 PM

You're only resisting downward (shear) forces at this connection point. You're not trying to keep the deck from pulling AWAY from the house, only transferring the loads from the live and dead load of the deck to the foundation of the house.

This is a very hot topic with engineered wood systems, and is subject to a lot of interpretation and opinion. So, I definately suggest checking to see what your inspector will require.

That being said, I see no need for the pictured product. Your neighbor did pretty well in putting in blocking to really give the lag bolts something to bite onto.

The house's rim joist itself has impressive strength in compression loads...The i-joists have very little strength themselves. That is why that rim board is required. I-joists alone can't take the weight of the walls/floor above and the roof. So, I think relying on the joist itself to in any way to support the deck is a flawed approach. I say use the rim board to your advantage.

Adding lumber behind the rim to catch the bolts is an excellent idea. You could also use carriage bolts, nuts, and washers instead of lags.

Bolt spacing is typically 16"oc for 1/2" bolts and 12"oc for 3/8" bolts. Check with your local municipality to see for sure. Some require more.

ONE THING TO CHECK!!!
You aren't attaching this deck to a cantilevered floor are you? If so, you're asking for problems with the connection from the rim board to the i-joists. With a cantilever, the house's rim can't transfer the deck's loads down to the foundation, so it transfers it to the i-joists (via the few nails at that connection point). Not good. You're basically reliant on the house's wall sheathing to carry the deck load. Once again, not good. This is one instance where good old 2x10's are better. Typically, this installation requires the installation of upside down joist hangers from the house's joists to the house's rim...Your local inspector will likely require evaluation by a structural engineer. It is best to ask first.

Ler0y Jenkins 05-05-2008 01:11 PM

Quote:

Originally Posted by thekctermite (Post 121090)
You're only resisting downward (shear) forces at this connection point. You're not trying to keep the deck from pulling AWAY from the house, only transferring the loads from the live and dead load of the deck to the foundation of the house.

This is a very hot topic with engineered wood systems, and is subject to a lot of interpretation and opinion. So, I definately suggest checking to see what your inspector will require.

That being said, I see no need for the pictured product. Your neighbor did pretty well in putting in blocking to really give the lag bolts something to bite onto.

The house's rim joist itself has impressive strength in compression loads...The i-joists have very little strength themselves. That is why that rim board is required. I-joists alone can't take the weight of the walls/floor above and the roof. So, I think relying on the joist itself to in any way to support the deck is a flawed approach. I say use the rim board to your advantage.

Adding lumber behind the rim to catch the bolts is an excellent idea. You could also use carriage bolts, nuts, and washers instead of lags.

Bolt spacing is typically 16"oc for 1/2" bolts and 12"oc for 3/8" bolts. Check with your local municipality to see for sure. Some require more.

ONE THING TO CHECK!!!
You aren't attaching this deck to a cantilevered floor are you? If so, you're asking for problems with the connection from the rim board to the i-joists. With a cantilever, the house's rim can't transfer the deck's loads down to the foundation, so it transfers it to the i-joists (via the few nails at that connection point). Not good. You're basically reliant on the house's wall sheathing to carry the deck load. Once again, not good. This is one instance where good old 2x10's are better. Typically, this installation requires the installation of upside down joist hangers from the house's joists to the house's rim...Your local inspector will likely require evaluation by a structural engineer. It is best to ask first.

Thanks for the quick reply. I called Timberstrand and spoke with a representative who referred me to a specification guide, which can be found here: http://www.ilevel.com/literature/TJ-4000.pdf

According to the representative and the specification guide (at page 10), the ledger can be through-bolted directly to the rim joist. Each carriage bolt can will hold 400lbs for 3/8" carriage bolts and 475lbs for 1/2" carriage bolts.

Regarding the deck pulling the rim joist out from the I-joists, the representative pointed out that the rim joist is also nailed to the sill plate on the bottom and the floor plate on the top, so pulling away shouldn't be an issue.

I think I'll just use 1/2" galvanized carriage bolts spaced in between each I-joist (approximately 20" apart). If the building inspector requires it, I'll add the blocking board to the back of the rim joist at each location. I think that may have been required only because my neighbor was using lag bolts rather than carriage bolts though.

Thanks again for the input.

Ler0y Jenkins 05-05-2008 01:21 PM

One more question. I'm assuming this Timberstrand stuff is different from OSB? I did some research and it appears that attaching a ledger directly to OSB is not recommended?? Is this correct?

concretemasonry 05-05-2008 01:35 PM

Deck Building Question - Installing Ledger Board to Rim Joists
 
Surprised some else did not suggest it, but have you considered a frees standing deck?

Many areas do not permit decks attached to ledgers because of all the other problems that untilmately go with that. - Sealing, flashing, etc. that is very difficult and costly to do properly. The result with a ledger attachment is frequently moisture, rot and mold and you become aware of it when it is too late to do anything about it.

Dick

Termite 05-05-2008 02:25 PM

Quote:

Originally Posted by Ler0y Jenkins (Post 121099)
One more question. I'm assuming this Timberstrand stuff is different from OSB? I did some research and it appears that attaching a ledger directly to OSB is not recommended?? Is this correct?

Timberstrand is a proprietary brand name. It is similar to OSB, but is stronger than conventional OSB rim. It can actually be used in some header and stair jack applications.

Better check on your bolt spacing. They need to be 16"oc, typically staggered up/down. It is easier to place a call and ask first!

Ler0y Jenkins 05-05-2008 02:27 PM

Quote:

Originally Posted by concretemasonry (Post 121102)
Surprised some else did not suggest it, but have you considered a frees standing deck?

Many areas do not permit decks attached to ledgers because of all the other problems that untilmately go with that. - Sealing, flashing, etc. that is very difficult and costly to do properly. The result with a ledger attachment is frequently moisture, rot and mold and you become aware of it when it is too late to do anything about it.

Dick

I contemplated doing a free-standing deck but I'll stick with the ledger board approach if I can lag directly into the rim joist (I'm just more familiar with that method).

Termite 05-05-2008 02:28 PM

Quote:

Originally Posted by concretemasonry (Post 121102)
Surprised some else did not suggest it, but have you considered a frees standing deck?

Many areas do not permit decks attached to ledgers because of all the other problems that untilmately go with that. - Sealing, flashing, etc. that is very difficult and costly to do properly. The result with a ledger attachment is frequently moisture, rot and mold and you become aware of it when it is too late to do anything about it.

Dick

Not a bad idea, but if this is a newer home, it can be an obstacle. The piers closest to the house will typically be in "disturbed" soil in what was the footing overdig, and will therefore not be effective. One must dig down to undisturbed earth to establish effective bearing. That is often in excess of 8 or 10 feet. Not practical for a deck!

I've read that it takes an average of 7 years for disturbed earth to reach the original level of compaction that it had before it was dug up. That all depends on a lot of factors though.

Ler0y Jenkins 05-05-2008 02:29 PM

Quote:

Originally Posted by thekctermite (Post 121109)
Timberstrand is a proprietary brand name. It is similar to OSB, but is stronger than conventional OSB rim. It can actually be used in some header and stair jack applications.

Better check on your bolt spacing. They need to be 16"oc, typically staggered up/down. It is easier to place a call and ask first!

I guess I could do them 16"OC. I think 20"OC is acceptable though because my other neighbor has a deck that was installed by the builder and that looks to be how his is attached (although I didn't measure).

I did call the building officer but he hasn't called me back yet. I want to check with him before I plan anything definitely. Thanks again.

Ler0y Jenkins 05-05-2008 02:38 PM

3 Attachment(s)
Here's another shot of the deck plans. Any input on how my beams/posts are arranged? I think the support will be sufficient but I wouldn't mind some input for the experts :thumbup:

Clutchcargo 05-05-2008 03:08 PM

What software did you use to design your deck?

Ler0y Jenkins 05-05-2008 03:26 PM

Quote:

Originally Posted by Clutchcargo (Post 121119)
What software did you use to design your deck?

I used Google Sketch-Up. It's a free program that can be downloaded here: http://sketchup.google.com/download

Unless you are familiar with CAD programs, I would suggest watching some of the online video tutorials to see how it works. I didn't and ended up redoing my design several times before I had a "workable" model that I could actually use.

MacRoadie 05-05-2008 04:30 PM

I'd check those footings below the stair. They look to be awful close together. Too close and the bearing capacity of the soil is compromised. The area of influence is typically a 45 degree angle out from the bottom of the footing in all directions and shouldn't overlap any adjacent footing.

Ler0y Jenkins 05-05-2008 05:07 PM

Quote:

Originally Posted by MacRoadie (Post 121138)
I'd check those footings below the stair. They look to be awful close together. Too close and the bearing capacity of the soil is compromised. The area of influence is typically a 45 degree angle out from the bottom of the footing in all directions and shouldn't overlap any adjacent footing.

I'm not sure I understand. The area of influence must be limited in some way or every footing would eventually interfere with another footing, right? What I mean is, even if the footings are ten feet apart, a diagonal line drawn at 45 degrees from the base of the footing will, eventually, intersect with the line drawn off of the other footing, right?


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