Through Flashing Single Wythe Masonry

[kch66]

NCMA has details for through wall flashing of for standard reinforced 8 inch cmu. This interrupts the bond of the mortar and grout at the base of the wall. The only transfer for the shear loads at the base of the wall is through the masonry dowels. Some locations are requiring through wall flashing for structural reinforced cmu walls. Just curious about opinions on using through wall flashing.

 

[msquared48]

An obvious thought of an Architect to solve a perceived problem, real or not, without consulting a Structural Engineer... Happens too much in my humble opinion.

Do the sections at the base of the wall show the dowels afterset into the foundation through pre-drilled holes in the flashing? This could be a problem if you had to develop a moment at the base of the wall - special consideration here...

Seems you are creating a condition for horizontal cracking and water intrusion with the presence of the thru-flashing - exactly what you are trying to prevent. Structurally, it does not seem to be a good idea and I would not do it.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[Ron]

Through-wall flashing is not necessary for single wythe masonry. It is necessary for multi-wythe and veneer applications.

 

[hokie66]

If you set the bottom of the CMU wall down below the floor level, it has the same effect as a through wall flashing, but without the structural discontinuity.