Structural masonry repairs require specific methods to ensure the building is repaired safely and built to last a long time. A lintel is a structural member placed above windows and doors to support the weight of the wall above. In the case of a brick masonry wall, lintels may consist of reinforced brick masonry, brick masonry arches, precast concrete or structural steel shapes. Lintels typically rest on top of the last brick course that is level or approximately level with the top of the window or door frame. The bricks above the wall opening on which the lintels rest can be strengthened by the installation of steel reinforcing bars.
The illustration to the right is an example of the beginning of the structural steel installation process. The finished process would show the brick being completed on the face of the CMU and extending up the columns of both sides of the steel lintels to create the bearing points.
Design & Structural Masonry Repairs
To eliminate the possibility of structural cracks in the wall above these openings, the structural design of the lintels should not involve the use of “rule-of-thumb” methods, or the arbitrary selection of structural sections, without careful analysis of the loads to be carried and calculation of the stresses developed. If these are not taken into account, problems of cracking and spalling could occur. Many of the cracks that appear over openings in masonry walls are due to excessive deflection of the lintels resulting from improper or inadequate design, or improper installation of the flashings.
Consideration must also be given to moisture control wherever there are openings in masonry walls. There must always be a mechanism to channel the flow of water to the outside. Flashing should be installed on the lintel to allow any water that might enter the masonry to filter out over the lintel. Some of the most common leaks occur over the windows because of improper flashing details.
Types of Lintels
There are several different types of structural steel lintels used in masonry. They vary from single angle lintels in cavity or veneer walls, to steel beams with plates in solid walls, to shelf angles in brick veneer panel walls.
Installation of steel lintels in masonry walls is a conventional construction operation. The walls are built to the height of the opening, the lintel is installed over the opening, and the masonry work is continued.
For more information on structural masonry repairs, contact Abbot Building Restoration at 617-445-0274 today.