Originally Posted By: roconnor
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I think your gut feeling about the strap anchors being inadequate may be right, because they typically must have a closer spacing to be equivalent to the anchor bolts.
The actual capacity of these strap anchors is established by the manufacturer, and the ICC has evaluation reports for most of them (like Simpson) as a substitution for the code required anchor bolts. The allowable capacity of a typical 1/2 anchor bolt depends on a lot of things (embedment, edge distance, wall strength, etc.) but is typically around 1,000# to 1,500# (IBC Table 1912.2), which is hard to match.
Most strap anchors just don?t have the same capacity (sometimes half the capacity unless they are the heavy duty ones), so you typically need more anchors at a reduced spacing. Manufacturers usually have tables for substituting strap anchors for anchor bolts, but some judgement is usually needed. Evaluating the required anchorage and what is equivalent to this is beyond a home inspection, and should be done by a building official or engineer.
If you are in an area with significant wind or seismic loading, and the strap anchors just don?t look right, it probably should be evaluated by an engineer.
Robert O'Connor, PE
Eagle Engineering ?
Eagle Eye Inspections ?
NACHI Education Committee
I am absolutely amazed sometimes by how much thought goes into doing things wrong