Masonry Resources

Question & Answer Section

Topic: Rebar Lap Splicing

Click here to Download Full PDF Version

Question:
How do you calculate correct rebar lap splicing to meet code?

Answer:
The IBC 2006 adopted MSJC 2005 by reference; however they decided to keep the previous lap lengths of 48 bar diameters. ...that engineers may have the option of using MSJC 2005 for their design lap lengths. Depending on the f’m the lap lengths can be shorter particularly in the smaller bar sizes. ...Footnotes (1) & (2) represent comments in the IBC code. (1) instructs the engineer on additional lap requirements in areas of high stress, (2) addresses the requirements for epoxy coated rebar. Footnote (3) assumes the bars are spaced at least 8” on center if the bars are closer the table will need to be adjusted. All bars are centered in the wall, if the bars are designed off center the table will need to be adjusted. The f’m is a variable that may be changed to meet your project requirements. The IBC 2009 has adopted MSJC 2008 including the lap lengths. These laps match the MSJC 2005 requirements so the MSJC laps should be what we see in the future.
Below is a lap splice spreadsheet, provided by Kelly Walker of the Masonry Institute of Michigan, which has been updated for IBC 2006 as adopted in MBC 2006. Also below, are the MSJC 2005 laps.

Submitted by Kyle Lochonic

With Support From:

Supporting Documents:

Required Lap Length of Bars in Inches

Click here for document

8" & 12" CMU (bar in center - rebar sizes #3 - #8)

Click here for document

www.mim-online.org


Topic: Locating CMU Control Joints (CJ's)		Click here to Download Full PDF Version

Question: What is the approximate spacing of Control Joints (CJ’s) for reinforced CMU? Answer: Using the Empirical Method in NCMA TEK 10-2B, Table 1 calls for a length to height ratio of 1.5 not to exceed 25ft. This assumes you have wire every 16” o.c. The engineering method in NCMA TEK 10-3 has different ratios but still does not exceed 20 or 25 ft. Kelly L.K. Walker Architectural Services Director Masonry Institute of Michigan, Inc.

Supporting Documents:
NCMA TEK 10-2C Control Joints For Concrete Masonry Walls - Empirical Method Click here for Tek Note

NCMA TEK 10-3 Control Joints For Concrete Masonry Walls- Alternative Engineered Method Click here for Tek Note www.ncma.org



Topic: Locating Brick Veneer Expansion Joints (EJ's)		Click here to Download Full PDF Version
Question: What is the approximate spacing for Expansion Joints (EJ's) for a typical brick veneer application? Answer: Please read the following supporting documents.
Supporting Documents:
BIA Tech Note 18A Accommodating Expansion of Brickwork Click here for Technical Note www.gobrick.com

Brick Expansion Joints and Wall Openings By: J Gregg Borchelt, PE Courtesy of The Story Pole Click here for article



Topic: CMU Wire Reinforcing		Click here to Download Full PDF Version

*Question:* What is the best wire for Single Wythe CMU and for Multi-Wythe CMU Cavity Wall? Answer: Contrary to popular belief, wire reinforcing today typically offers no structural stability. In fact, the primary purpose of wire reinforcement in modern masonry wall systems is simply to help resist CMU shrinkage cracking. Typically, vertical and bond beam rebar reinforcement serves to resist wind loading. Truss wire is not recommended for use is reinforced CMU. Diagonal cross rods make it impossible to meet modern grouting standards referenced in the IBC and sub-referenced in ACI Building Code Requirements for Masonry Structures. Ladder wire with cross rods spaced 16 inches on center allows code required centering of rebar, freer flow of grout and promotes full embedment in mortar at every intersection where side and cross rods meet on the inner and outer CMU face-shell, resisting wall shrinkage.
Supporting Documents:
Climb the Ladder To Improve Wall Reinforcing Design Written by Kyle Lochonic & Jeff Snyder and is published in the Masonry Magazine. Click here for article
Building Code Requirements and Specification for Masonry Structures Reported by the Masonry Standards Joint Committee (MSJC) Click here for Building Code Requirement
NCMATEK 12-2B Joint Reinforcement For Concrete Masonry Click here for Tek Note
NCMA TEK 12-1A Anchors and Ties for Masonry Click here for Tek Note www.ncma.org



Topic: CMU Wire Reinforcing		Click here to Download PDF Version

*Question:* Is wire reinforcement with 3/16 inch diameter side rods or 3/16 inch diameter side and cross rods better than standard 9 gauge side and cross rods? Answer: No, for the most part it is just the opposite. The primary purpose for wire in todays reinforced walls is to reduce CMU wall shrinkage. It is very difficult to surround 3/16 inch diameter wire with mortar when placed in 3/8 inch bed joints. This is especially evident when considering allowed tolerances for masonry units and joint sizes. Mortar better surrounds wire when utilizing 9 gauge flush welded side and cross rods, increasing resistance to shrinkage cracking. It is no surprise demand for truss wire has fallen significantly in the last decade. The market simply demands higher performance 9 gauge 16 inch core-clear ladder!
Supporting Documents:
TECH Talk Daniel S. Zechmeister, P.E. Executive Director Masonry Institute of Michigan, Inc. Click here for article www.mim-online.org
Selecting the right reinforcement for the job Mario J. Catani Click here for article