What Is Precast Concrete Lintels?
What Is Precast Concrete Lintels?
Precast concrete lintels are horizontal members used in residential and commercial buildings of concrete masonry to span openings in the walls.
They function as beams, supporting the weight of the wall, dead and live loads over the openings, and transmitting these loads to adjacent masonry.
Precast concrete lintels come in various sizes and shapes depending on their purpose. York Building Products has been manufacturing precast concrete lintels for over 60 years with tight tolerances due to their production experience.
Lintels are an essential part of any concrete masonry construction. They serve as beams to support the weight of walls and other loads over an opening, and their rigidity, strength, durability, fire resistance and aesthetics make them ideal for this purpose.
Precast reinforced concrete lintels and reinforced concrete masonry units are the most common types used. Their color and surface texture can be selected to add an aesthetically pleasing accent or to match with the surrounding masonry.
Precast Concrete Lintel Installation
Precast concrete lintels should be installed according to the manufacturer’s instructions. The precast flooring units should be laid on a mortar bed across the whole wall width and not dragged over supports.
It is important to ensure that the top of the lintel is clearly marked whenever possible in order to prevent improper installation in the wall. Additionally, recommended bearings are 100mm for openings up to 1m and 150mm for openings over 1m.
Precast Concrete Lintel Sizes
Precast concrete lintels come in a variety of sizes, including 4×8, 6×8, 8×8 and 10×8. The actual height of the lintel is 7-5/8 inches to coincide with the typical course height. A modular lintel length should be specified with a minimum length of the clear span plus 8 inches (203mm) to provide at least 4 inches (102mm) bearing at each end. To determine lintel dimensions, load tables are based on a minimum of 8” bearing and minimum concrete cover over reinforcing steel.
Precast concrete lintels are manufactured to certain dimensions, corresponding to the size of the masonry units being used. A minimum length must be chosen which is equal to the clear span plus 8 inches (203mm), in order to provide 4 inches (102mm) bearing at each end.
For lintels that may be subjected to tension during handling, transportation or placement, steel reinforcement should be added on both its top and bottom with a concrete cover of 1 and a half inches (13mm). The lintel width should match that of the supported wythe of masonry.
It is also recommended for them to be clearly marked on the top for proper installation into the wall.
What Are The Two Advantages Of Precast Concrete Lintel Over In Site Lintel?
Precast concrete lintels have several advantages over in-site fabricated lintels. Firstly, precast lintels are more sustainable due to the reduced quantities of cement and aggregates required for its production. This reduces cost as well as the impact on the environment.
Furthermore, enhanced quality control in prefabrication increases the durability of the lintel and ensures consistency with other components of a building.
Additionally, it reduces the cost associated with formwork while providing a quicker turnaround time in construction compared to traditional methods of on-site fabrication.
Finally, labour costs can be minimised by using precast concrete due to less manpower being needed for installation, thus making precast concrete an efficient and viable choice for construction projects.
Precast Concrete Lintel Load Capacity
Precast concrete lintels are designed using the strength design provisions of Building Code Requirements for Structural Concrete, ACI 318-99.
The width of the lintel should equal the width of the supported masonry wythe and reinforcement is normally Grade 60 (60,000 psi specified yield strength) steel. Nominal lintel strength is determined based on the strength design provisions of ACI 318 and then reduced by strength reduction factors called phi ( ) factors.
Tables 1 through 4 list design moment and shear strengths for various precast lintel sizes and concrete strengths, with an 8×8 in. (203 x 203 mm) lintel having sufficient strength when two No. 4 (13M) bars and f ‘c = 4000 psi (20.7 MPa) are used.