Masonry Opening without Lintel

[Den32]

What is the maximum size (length) opening you would allow in Masonry without at Lintel?

The specifics are:
- Clay (brick) masonry load-bearing walls (3 or 4 wythes thick). Old historic building, early 1900's.
- Interior bearing walls (2 storey building with wood floors & roof)
- Penetrating walls with various size ducts

Obviously 1 to 2" diameter pipe is no issue, but there are duct openings ranging from 8" to 48" wide. The larger openings (24" to 48") will get Steel Lintels for sure, but the 8" to 12" range, I am unsure.

I looked briefly thru BIA Tech notes & ACI 530 and couldn't find anything. In Masonry Designers Guide (2nd Ed), Section 15.4.8 says >12" needs a lintel and references a Code Section 9.9.1 (which is old ACI 530-95, and there is no such section in ACI 530-08).

 

[MiketheEngineer]

Theoretically the bricks will fail at a 45 degree angle from the corners up to the center. Example: a 12'' opening will fail in a triangle that is 12'' by 66' tall.

If a brick fits in that zone - it could fall out. If the mortar is still any good - it won't but who knows..

 

[csd72]

Where I come from they use arch bars below about 900mm (3 feet) the proper ones are precambered slightly but a flat plate of steel can also work.

if you used a plate less than the mortar bed thickness then it could be slotted into the wall prior to demolishing the hole.

 

[ToadJones]

A triangle that is 66 feet tall and 12" wide?

 

[msquared48]

Exaggerated Mayan Arch Toad...

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

 

[ToadJones]

Nice Mike-
That had me laughing out loud.

 

[rscassar]

I wouldn't take out anymore than 1 brick without providing a lintel.

 

[a2mfk]

I'm with kikflip. I am sure we have all seen lots of different masonry openings without a proper lintel, and we understand that they work as an arch. BUT, I am not signing off on much over one block or brick either!

 

[Den32]

I was thinking the same thing, 8" max opening without lintel, especially since this is older brick.

thanks for opinions.