Ledger attachment to engineered rim board 2

[mattradk]

Can 2x deck ledger boards be lag screwed directly to 1-1/8" engineered lumber rim boards (under 1/2" sheathing) without extra reinforcement? The American Wood Council’s DCA6 Prescriptive Residential Wood Deck Construction Guide seems to suggest that they can while other resources cite tear-out concerns.

 

[dik]

I don't see why not... the LVL or PSL and sheathing should offer excellent resistance; I'm not aware of the tear out concerns.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[phamENG]

This is just one manufacturer, but it's good info: Link

 

[mattradk]

Well, it was pretty clearly stated at the link you provided. The Prescriptive Residential Wood Deck Construction Guide also provides specs for fastener spacing for LVL's that includes Boise, Weyerhauser and other manufacturers. So, it appears to be permitted.

Thank you both for your assistance.

 

[dik]

pham did all the work...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[phamENG]

Or was I just avoiding work?

Using Google (or any other search engine) is all about knowing the right keywords.

Glad it helped.

 

[JLSE]

My understanding, is the 'tear out' is addressed by the use of the tension tie specified in the line provided...... they(Weyerhaeuser) are assuming, that the engineer ties this connection into the diaphragm. Bottom line is yes, 'tearout' is an issue that needs to be considered. It is a failure mechanism.

 

[phamENG]

JLSE - that tension tie is a lateral connection to tie the deck diaphragm (composed of all the little moment couples of the decking to the joists or discreet bracing) to the building diaphragm. The idea being that you end up with a 3-sided diaphragm for the deck. The ledger is one side, and the two perpendicular sides are tied with the tension tie to form the other three sides. Then the deck cantilevers from the building.

Tear out would be a concern that the composite material can't handle the bolt load shear (either from lateral loading or gravity loads).

 

[JLSE]

phamENG
Ok, then I made a false assumption about what mechanism you were discussing... but my main point is the same; LTB of the rim is a design consideration, and adding tension ties at an interval, not just at the ends, will help prevent that failure. (The three sided concept you reference, is fine for the main lateral system.) Subpoint being, dont just go off of the Weyerhaeuser site page referenced, because it was not intended to be an all inclusive standard.

 

[phamENG]

JLSE - agreed. DCA6, published by the AWC, is a fantastic reference. It doesn't cover all eventualities, but it does cover 90% of the decks out there and addresses all of details needed to prevent the typical mechanisms. I usually reference it in my specs/notes and make compliance with the details mandatory on my projects. (Saves a ton of time, and makes it an easier pill to swallow for the contractors who get angry that I'm "over engineering" it because it's "just a deck."

 

[JLSE]

phamENG - decks.... supposed to be so easy. Always underestimated.

 

[mattradk]

DCA6 and all of your suggestions have been very helpful. I drew a lot of design requirements from DCA6, and even required compliance with it as well as the building code. It's "just a deck" but it was a pain when you throw in the use of Trex and connecting the ledger to the house's engineering rim board. The Trex manual has it's own requirements (like 12" separation for deck risers) to be aware of. I spent more time than I planned on it.

 

[phamENG]

mattradk - usually when somebody asks me to design a deck, I tell them to use DCA6 and call me if their design doesn't fit the canned details because they won't like my price.

 

[bones206]

I'm designing an addition and was looking to use this exact detail at the new roof/old roof junction. All I could find in the literature were prescriptive and in the context of decks. Is there a methodology available to do this as an engineered design rather than a prescriptive design? From my research so far, it appears the prescriptive ledger design is based on testing.

 

[phamENG]

bones - not sure you'd need to. If the testing works on the deck, I wouldn't think the results would be significantly different for a roof with the same connection detail. Maybe do a few NDS bolted connection calculations and see how the plf capacity of the two compare?

 

[dhengr]

Prescriptive codes are usually based on historical usage, good experience with reasonable success, engineering design and testing. But, they also tend to be somewhat conservative in their intent and approach. This is because the code writers understand that these codes will be used, applied and interpreted (or maybe misinterpreted) by a bunch of people (builders?) who probably don’t have much engineering knowledge and experience as part of their basis for their interpretation or misinterpretation of the needs and intents of that code. Usually, a well engineered solution will involve lighter members, fewer connectors, longer spans, etc., or alternatively, that the prescriptive solution can carry more load than the basic code tabulation or approach would indicate or allow. Prescriptive codes usually imply that you can build this particular element or structure, this way, reasonably safety, as long as it all falls within these bounds of loading, span length, etc., etc. There are usually a number of engineering considerations which the prescriptive codes brush over rather lightly. One example is that the rim board must be well fastened (nailed) to the top pls. of the wall below, and to the fl. sheathing above, or it can be pulled, ripped, right off the bldg. The upshot here, is that the lateral and vert. loads from the deck or new roof must be adequately taken back into the fl. diaphragm, or bldg. structure beyond/behind. These types of ledgers should not be applied over siding or foam insulation, and the like, but rather let-in to bear on the bldg. wall sheathing, or the rim board directly. And, great care is needed to detail and provide adequate ledger flashing tied into a proper weather, vapor, water plane system.