SF Permits MCP Server

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Edwin M. Lee, Mayor
Tom C. Hui, S.E., C.B.O., Director

City and County of San Francisco
Department of Building Inspection

INFORMATION SHEET
NO. S-03
DATE : December 18, 2013
CATEGORY : Structural
SUBJECT : Tension Anchors in UMBs
PURPOSE : The purpose of this Information Sheet is to establish guidelines for
reviewing tension anchors in UMBs
REFERENCE : 2013 San Francisco Building Code
Chapter 16C Seismic strengthening provisions for Unreinforced Masonry
Bearing Wall Buildings
Section 1705.19 Bolts Installed in Existing Masonry or Concrete
AB-046 Special Inspection and Structural Observation Documentation
DISCUSSION

PROCEDURE IN REVIEWING UNREINFORCED MASONRY BUILDING PERTAINING TO
TENSION ANCHORS:

When reviewing Unreinforced Masonry Building projects covered under Chapter 16C of the San
Francisco Building Code, the following guidelines outlined below should be adhered to:

Tension Bolts, as specified in section 4.b. of Table 16C-E of the current San Francisco Building
Code, are specified as “extending to the exterior face of the wall’. The allowable load for these
bolts is listed as 1,200 pounds. It was recommended that inclined tension anchors need to extend
within 1 inch of the exterior face of the masonry wall.

Although some epoxies and/or resins available would be able to develop the 1200 pounds of
tension in a shorter length, it is imperative that all inclined tension anchors used to satisfy section
4.b. of Table 16C-E of the current San Francisco Building Code are embedded as required, to
within 1 inch of the exterior face of the masonry wall. These anchors not only need to transfer this
minimum amount of tension, they also act to tie the multiple wythes of an unreinforced masonry
wall together into a single unit. Embedments shorter than that specified in the code may lead to

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Technical Services Division
1660 Mission Street — San Francisco CA 94103
Office (415) 558-6205 — FAX (415) 558-6401 — www.sfdbi.org



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INFORMATION SHEET S-03

delamination of the outer wythes of an unreinforced masonry wall. This delamination can lead to
falling hazards and can also result in overloading the remaining wythes of masonry, resulting in a
possible compression failure of the masonry wall.

(tr \-/1/ (3
Tom C. Hui, $.E., C.B.O. Date

Director
Department of Building Inspection

This Information Sheet is subject to modification, at any time. For the most current version, visit our

website at http:/Avww.sfdbi.org

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Technical Services Division
1660 Mission Street — San Francisco CA 94103
Office (415) 558-6205 — FAX (415) 558-6401 — www.sfdbi.org