Avoiding Cracks in Stack Bond Toronto 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 Toronto, why wouldn't the vertical joints in stack bond be as strong as the horizontal joints in both stack bond and running bond?

ATARCHITECT
(416) 822-0365
955 QUEEN STREET W
TORONTO, ON
 
Amsted Construction Limited
PO Box 129
Stittsville, ON
Services
Custom Builder, Designer / Architect, Remodeler

Data Provided by:
Al White Landscaping & Excavating
(613) 966-4482
45 Wilson Av
Belleville, ON
 
J David McAuley Architect Inc
(519) 823-2441
360 Woolwich Street
Guelph, ON
 
Cortes J L Architect Corporation
(519) 743-4330
222 King S
Waterloo, ON
 
Menno S. Martin
PO Box 508 / 1185 King Street N.
St. Jacobs, ON
Service Type
Designer / Architect, Remodeler
Membership Organizations
Better Business Bureau, Canada Green Building Council, Ontario Home Builders' Association, Renovators Mark of Excellence

Data Provided by:
Christopher Z Tworkowski Architect
(705) 652-1646
44 Bridge
Lindsay, ON
 
Legault Sod Farms
(705) 268-8873
660 Sandy Falls Rd
Timmins, ON
 
Better Blinds & Decor
(519) 212-7277
7 Flora Street
Cambridge, ON
 
De Berardis Associates Incorporated
(905) 660-8877
207 Edgeley Boulevard
Vaughan, ON
 
Data Provided by:

Avoiding Cracks in Stack Bond

Provided By:

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.

Click here to read full article from Masonry Construction