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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Finney M B Limited
(705) 324-4418
Suite 213 189 Kent St W
Lindsay, ON
 
Salter Pilon Architecture Inc
(705) 737-3530
151 Ferris Lane
Barrie, 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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Designer / Architect, Remodeler
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Better Business Bureau, Canada Green Building Council, Ontario Home Builders' Association, Renovators Mark of Excellence

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Lyle Architects
(705) 474-1784
261 Regal Road
North Bay, ON
 
Grinham L Alan Architect Inc
(519) 766-1580
20 Douglas Street
Guelph, ON
 
Architectural Design Associates Inc
(519) 254-3430
100-1880 Assumption Street
Windsor, 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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