MASONRY Q & A :: What is the masonry standard or preferred for a brick veneer bearing on a steel lintel? 4" or 8" bearing?
Lintel bearing for veneer is covered in TMS 402 Chapter 12. Specifically 220.127.116.11.2 states "not less than 4 inches". Your architect/engineer should size it for you. Keep in mind that if it is anchored to the backup you must install and expansion joint at one end minimum. If the opening is very wide you may need an exp jt at both ends. I hope this helps. If not, call me. Thanks for allowing your MAF/MCAA to help.
Jerry Painter, FASTM
Brick, Block & Beers: Vol II Issue II- Masonry Best Practices: Control Joints for Concrete Masonry walls
The pictures provided show cracks under the precast header bearing at what appears to be both ends of an opening. These cracks then turn and extend up to the top of the wall through the course above the precast in a stair step fashion. The third picture provided shows cracking under the end of a precast sill which then extends from the lower right hand corner of the opening down the wall in a stair step fashion.
My response to this inquiry is based strictly on the 3 pictures provided. There may be other extenuating circumstances that I am not aware of.
The pictures provided are so indicative of classic masonry shrinkage cracking that I intend to catalog and use them in future presentations to show where cracking usually shows up in structures where shrinkage of the masonry has not been addressed by either horizontal reinforcing or properly placed control joints.
MASONRY CONSTRUCTION & INSPECTION WORKSHOP