Avoiding Cracks in Stack Bond Edmonton AB

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 Edmonton, why wouldn't the vertical joints in stack bond be as strong as the horizontal joints in both stack bond and running bond?

Holland Roth Architects
(780) 424-2171
10914 105 Avenue Nw
Edmonton, AB
 
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9834 105 Street Nw
Edmonton, AB
 
R Saunder Architects Ltd
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12125 Jasper Avenue Nw
Edmonton, AB
 
Castle Built Homes
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Edmonton, AB
 
G C Can Limited
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210-12 St Joseph Street
St Albert, AB
 
Kasian Architecture Interior Design and Planning Ltd
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251-10150 Jasper Avenue Nw
Edmonton, AB
 
Brinsmead Kennedy Architecture
(780) 488-9700
10434 122 Street Nw
Edmonton, AB
 
Richard Fairbank Architect Ltd
(780) 988-6471
10020 82 Avenue Nw
Edmonton, AB
 
S Siren Architect Ltd
(780) 459-2950
100-17 Boudreau Road
St Albert, AB
 
Millennium Building Systems
(780) 460-9665
Box 206 3-11 Bellerose Dr
St Albert, AB
 

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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