Residential Deck Ledger attached Through Masonry 1

[pcellc]

I have run into a recent question regarding the attaching of a residental deck ledger board to a wall that consists of Brick masonry veneer over typical wood framed construction. The detail provided shows thru-bolting the ledger through the veneer into the wood structure behind. It has recently been questioned that this may violate the IRC code section R703.7.3 which states that masonry veneer shall not support any vertical load other than the dead load of the veneer above.

The arguement is that the bending of the bolt will transfer a vertical load to the brick veneer, hence violating the code. However this load transfer would not exceed any of the allowable compressive forces in masonry as the shear perpendicular to the grain of the ledger board itself would control in the the design. Therefore in my opinion the load applied to the masonry is negligible as it is really being transfered back to the wood structure.

What are your opinions on this? And Can you suggest a better detail for fastening a ledger in this application?

 

[AlmostPE]

I think you are suppose to stop and start the veneer. So stop the veneer below the deck, do another angle right above the deck and start the veneer again.

 

[JMirisola]

If the placement of the ledger is just above grade, use posts and pier pads to support the ledger vertically, while still going through the masonry into the wood with lag bolts for a positive connection to the main structure. You could, I suppose, do the same for a higher deck, but it would come down to aesthetics at that point.
It would be no easy feat, but you could remove x rows of brick and recess the ledger.

Jeff Mirisola, CSWP

http://designsmarter.typepad.com/jeffs_blog

Dell M90, Core2 Duo
4GB RAM
Nvidia 3500M

 

[woodengineer]

Putting the brick issue aside; it is best to design desi.gn the deck system as free standing. Virginia Tech has done a great deal of research on the subject matter as well as attachment of rail posts to deck. I would definitely design the deck as free standing.

woodengineer

 

[msquared48]

Free standing is good in theory, but in a seismic event, due to the different periods of the separate structures, you will get hammering withont an adequate seismic joint between the two. This could be unsightly and architecturally undesirable. (Why am I concerned about what an Architect thinks?)

If the bolts go thru the brick with columns holding theledger, you still have the problem of lateral forces parallel to the ledger bearing laterally on the veneer before any force gets to the wood studwall. The brick is so stiff relative to the studwall that it would end up taking the shear from the deck. Brick veneer is not designed to do that.

Professionally, I feel that the best solution is to stop and start the veneer as mentioned by AlmostPE. That way neither the vertical or lateral loads are taken by the brick, only by the wood studwall.

Mike McCann
McCann Engineering

 

[concretemasonry]

Through bolting the brick requires tightening the nuts that could also compress the wall ties if it is a typical "brick over stick" construction. The compression of the ties could distort and crack the brick veneer.

Any decent detail will require flashing to run up behind the primary moisture barrier to eliminate the common leakage, rot and mold problems. This necesitates removing the brick, so why not make a direct attachment if that is what the client wants. Any bolt holes in the flashing must also be addressed. It is a poor second chice when compared with a free standing deck because of the possibility of water penetration.

Dick

 

[MiketheEngineer]

IF I am not mistaken - the latest IBC will require a 1,500 connection between deck and house at each end.

I think Simpson has already designed one....

 

[msquared48]

I assume you mean a 1500 pound connection, as in tension, compression...? This also implies the development of shear through the use of lag screws/bolts into the ledger at the house.

Delete the brick at the ledger, caulk and flash well.

Mike McCann
McCann Engineering

 

[HouseBoy]

"the load applied to the masonry is negligible as it is really being transfered back to the wood structure"
I don't see how his can be true. Regardless of how "negligible" the load on the brick is (from the bolt) it still is applied to the brick.
Also, my understanding of the 1500 lb load is that it is a horizontal force applied at each end of a deck, perpendicular to the face of the wall.
Caulk is not going to last long without maintenance.

 

[twinnell]

I don't think I have ever seen the brick stop at the deck of a house. So the deck ledger is bolted to the house band. The distance from the inside face of the deck ledger to the outside face of brick is approximately 4 inches. Therefore the deck joists run under the brick veneer 4 inches. The house band is exposed. How do you flash that? Do you have to use a treated house band?

 

[HouseBoy]

This is a potentially significant problem. The IRC is quite specific about it and I've seen many building departments that adhere to it well. Unfortiunately in my area (Cincinnati Ohio) the local officials have exercised the practice of IGNORING the code requirement. (This is frustrating).
Anyway, we try to encourage compliance with the code even if the building authority does not demand it.

I would like to hear more from pcellc and others about how this load is negligible. I would suppose the bearing of the bolt on the masonry is not the weak link. Lateral forces (both in plane and out of plane) on the brick veneer seem like they would be the significant problem. You can't get these loads into the wood frame without first imparting them onto the brick.

 

[msquared48]

OK, so the flashing is a problem.

In order not to bear on the brick laterally or vertically then, the only option I see, as mentioned previouslybu woodengineer, is a column and knee-brace or X brace system at the intersection of the deck with the house. This may look like H&^*, but it works.

This is the only way I see for the vertical and lateral loads to avoid having to be transmitted to the existing structure, and there is no flashing problem.

Mike McCann
McCann Engineering

 

[jheidt2543]

This has been an interesting thread and I would like to add a few thoughts that come to mind as I read it:

1. Stopping and starting the brick veneer to install the angle seems to creat more problems than it solves; problems of moisture, vermine, and insulation/heat transfer.

2. A bent lag bolt, IF it bends, laying on a 4" brick doesn't seem to me to be the problem, I would think it would tear out of the stud before crushing the brick.

3. Assume a 4x4 angle with lag bolts at 32" o.c., I think you could consider the steel angle as a large 32" x 4" washer resting against the brick. For a 12' wide deck, the vertical load on the angle would be (6')x(50psf)=300 plf. The tension load on the bolt would be ((300plf)x(2.67')x(.17'))/.17 = 801 lbs. which would be (801)/(4)*(32) = 6.3 psi on the brick - not much to worry about.

4. How about the tension load on the lag bolt of 801 lbs? Depending on the wood member's specific gravity, a 5/8" or 3/4" lag would give 400 lbs/in of penetration (AITC p.5-56).

Unless I've missed something, I really don't see the problem.

 

[HouseBoy]

"IF it bends"?
Are you suggesting that alag screw embedded 1 1/2 inches into a rim joist and 1/2 inch into the plywood sheathing is going to cantilever across the air gap and the thickness of the brick and support the deck ledger? I assume you are not. Therefore, the bolt can not avoid but to bear in the brick veneer. Considewring that brick veneer is specifically indicated in the building code to be prohibited from supporting vertical load other than it's own dead weight, some would consider that a problem.

Additionally, I suspect it would be difficult to flash a lag screw penetration and the withdrawl capacity of a lag screw would be reduced over time due to moisture infiltration.

Resistance of a rim joist to horizontal loads normal to the face of the wall may also be considered dubious by some.

 

[tmills]

This is how we handle this detail.
First though;
1. You cannot support a deck directly through brick veneer. It is a code violation. You can damage the veneer and the bolts will rust out. Its a dangerous practice.
2. You cannot support a deck directly to the ends of open web floor trusses regardless of the veneer. It is a code violation and unsafe.
3. Starting and stopping the veneer is cumbersome and may result in wall leaks and veneer cracks later.

For a brick veneer the deck has to be either free standing or it should be attach to the structure using wood or steel spacers at each of the through bolt locations. A 4x or tube steel spacer the depth of the veneer plus the cavity depth and plus 1/4" x 9" or 11" long is placed at each through bolt location (typically 24" o.c.). The ledger is solidly bolted to structure with two or three bolts through the ledger and spacer and band board. The brick veneer goes on past behind the ledger and is not loaded in any way. Its best if the predrilled spacers are temporarily held in place to the band with a couple of bolts while the mason does his work then the deck contractor can drill the ledger from the back side through the band to align with the spacer holes. There needs to be through wall flashing at each spacer location. Its good if the top of the ledger aligns with a mortar joint so the spacers are easy to flash.

Virginia Tech has just published new deck attachment research for open web floor trusses. It is worth reading.

Tim

 

[HouseBoy]

Thanks tmills.
Do you have a better link to the VT article?

 

[tmills]

Go to this website:

http://www.sbcindustry.com/images/technotes/T-DeckLedger_07.pdf

Tim
TAM Consultants

 

[msquared48]

TMills:

Good article, but it does not detail brick veneer specifically. However, you present a good addition in thinking.

One further thought on your solution, I would use a non shrink epoxy grout between the bolt and steel pipe/tube member to preclude the problem of bolt bending from vertical and lateral loads.

Other than that, good solution. Thanks.

Mike McCann
McCann Engineering