Avoiding Cracks in Stack Bond Windsor ON

I have heard that masonry laid in stack bond is more likely to crack than masonry laid in running bond. Why? Assuming walls were built using the same mortar and brick in Windsor, why wouldn't the vertical joints in stack bond be as strong as the horizontal joints in both stack bond and running bond?

Architectural Design Associates Inc
(519) 254-3430
100-1880 Assumption Street
Windsor, ON
 
McLean & Associates Architects
(519) 977-5512
1570 Wyandotte Street East
Windsor, ON
 
Amsted Construction Limited
PO Box 129
Stittsville, ON
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Architecture Incorporated Architect
(519) 746-1003
490 Dutton Drive
Waterloo, ON
 
Thia Design
(705) 476-8466
183 First Avenue West
North Bay, ON
 
Glos Associates Inc
(519) 966-6750
3535 North Service Road East
Windsor, ON
 
Menno S. Martin
PO Box 508 / 1185 King Street N.
St. Jacobs, ON
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Architectural Design Associates Inc
(519) 254-3430
100-1880 Assumption Street
Windsor, ON
 
Brian Williams Architect
(905) 875-3124
176 Sarah Street
Milton, ON
 
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Milton, ON
 
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Avoiding Cracks in Stack Bond

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Source: MASONRY CONSTRUCTION MAGAZINE
Publication date: August 1, 1994

I have heard that masonry laid in stack bond is more likely to crack than masonry laid in running bond. Why? Assuming walls were built using the same mortar and brick, why wouldn't the vertical joints in stack bond be as strong as the horizontal joints in both stack bond and running bond?

Unreinforced stack bond walls are more likely to crack vertically than walls built with running bond. That is why ACI 530 requires any masonry laid in other than running bond to have horizontal joint reinforcement spaced no further than 4 feet apart in order to control cracking.In a running bond wall, any vertical crack must either pass through a brick at every other course or follow the mortar through head and bed joints. Usually the weakest path is through the units. Therefore the wall's strength is determined mainly by the strength of the units, not the mortar bond strength at head joints. In stack bond walls that are not reinforced, resistance to vertical cracking depends solely on mortar-to-brick bond, which is weaker in vertical joints than in horizontal joints. Better bond is developed in horizontal joints because the weight of the masonry keeps the joints under pressure throughout construction. If cracks do develop, they generally are very small because of this compression.

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