APA Narrow Wall anchorage 1

[MattJM]

Can the typical APA Narrow Wall (without holdowns) be anchored into hollow CMU foundation walls that do not have any ties (e.g. rebar) to the CIP foundation? The cells with the anchor rods will be grouted, of course.

 

[FSS]

You have to follow the load to the foundation. The narrow wall assembly takes care of the wall part. You have to deal with the rest.

 

[MattJM]

Thanks. I should have been more specific in my question:

A. The APA details only show anchorage to "foundations" - which can mean a foundation wall I suppose. The anchorage is per R403.1.6, which I believe contemplates anchorage to concrete footings. The engineering aside, does anyone know if it is generally "allowed" to anchor to a few grouted cells or does the IRC require anchorage into a footing proper or a wall tied to a footing?

B. The local building official allows contractors and builders to staple a copy of the APA detail to the permit plans, which shows what appears to be a minimal amount of anchorage. It seems that basic mechanics of the portal frame can result in significant uplift at one end (less any gravity loads). What am I missing that allows holdowns to be generally not considered for these types of walls?

Thanks all

 

[FSS]

The APA detail shows a min 4200# tie-down device requirement and references the embedded strap type. Someone has to make sure there is something there to anchor to and get required capacity. When I need this detail, I make sure to show whatever foundation requirements I need. If CMU stemwall is part of support, there had better be reinforcement as part of the deal.

 

[ctcray]

The 4200lb hold down device is for the Alternate Braced Wall Panel.

As long as the rimboard and the sill plate are connected properly to the foundation wall, the Narrow Wall bracing only needs to be connected to the rimboard with 2 metal plate connectors yielding 670lb each (See Figure 3 of APA's "Whole House Wall Bracing" brochure available from

http://www.wallbracing.org,

or in the 2007 Supplement to the IRC available here (see Figure R602.10.4.6 on page 56):

http://www.iccsafe.org/cs/codes/2007-08cycle/2007Supplement/IRC07S.pdf.

The Wall Bracing section of the IRC was completely rewritten (and therefore the entire sections is available in the above link) to help clarify and simplify the wall bracing provisions. So, although this may Post-date the code you are using, I think it does a good job of explaining what they meant in the first place.

These details are PRESCRIPTIVE, so are not necessarily easy to justify by calculations.

 

[MattJM]

Thanks again. Yes, the APA narrow wall detail does not require hold downs or any specific capacity, but rather only sill bolts per R403.1.6. However, the detail also has this:

Note: This narrow wall bracing segment meets the minimum requirements for wall bracing (racking loads in the plane of the wall.) The building designer should determine what specific details are necessary to provide a complete load path for using this bracing in the structure.

The load must go somewhere, so there you have it.