Lintel Block Sizing Calculator
Determine the correct lintel block or steel angle size for openings in masonry walls. Covers doors, windows, and garage openings with bearing calculations.
Results
Visualization
How It Works
The Lintel Block Sizing Calculator determines the correct lintel block or steel angle needed to safely support the weight above openings in masonry walls, such as doors, windows, and garage entries. Proper lintel sizing is critical because undersized lintels can crack, sag, or fail, compromising structural integrity and allowing water infiltration. This calculator accounts for opening width, wall height above the opening, and wall construction type to recommend an appropriate lintel size.
The Formula
Variables
- Opening Width (feet) — The clear horizontal span that the lintel must bridge, measured in feet. Larger openings require stronger lintels because the weight is concentrated over a greater distance.
- Wall Height Above Opening (feet) — The vertical distance from the top of the opening to the roof or next floor. Greater height means more dead load pressing down on the lintel.
- Wall Type — The masonry construction method: 8-inch concrete masonry units (CMU), brick veneer, or 12-inch CMU. Different wall types have different weights per square foot, affecting the load calculation.
- Dead Load (psf) — The weight of the wall material per square foot. 8-inch CMU weighs approximately 55 psf, brick veneer approximately 38 psf, and 12-inch CMU approximately 80 psf.
- Bearing Length (inches) — The horizontal distance a lintel must rest on the masonry on each side of the opening. Building codes typically require 8–12 inches of bearing per side depending on lintel type and load.
Worked Example
Let's say you're installing a garage door opening that is 16 feet wide in a concrete block wall (8-inch CMU). The wall height above the opening is 4 feet. First, calculate the total load: 4 feet (height) × 55 psf (8-inch CMU weight) × 16 feet (width) = 3,520 pounds total. Divided by the 16-foot opening width, this equals 220 pounds per linear foot of lintel bearing. Based on this 220 plf load, the calculator would recommend a lintel such as a double 2×12 wood beam with proper bearing, a steel angle lintel (like a 6×6×½ inch steel angle), or a reinforced concrete bond beam. The lintel must also extend at least 8–12 inches into the masonry on each side for proper support.
Practical Tips
- Always verify local building code requirements before ordering a lintel—codes vary by region and some jurisdictions require specific lintel types or may have snow load, wind load, or seismic considerations that increase requirements.
- Account for future loads when sizing lintels; if you might add another floor or heavy equipment later, size the lintel for that anticipated load rather than just current conditions.
- Ensure adequate bearing length on both sides of the opening; a lintel that's too small in size but rests on insufficient width of masonry can still fail by crushing the supporting blocks or bricks.
- For brick veneer over CMU, remember that the veneer adds weight to the calculation—use the combined wall type weight, not just the CMU weight alone.
- Steel angle lintels may require flashing and drainage provisions to prevent water from sitting on top and leaking into the building; consult with a mason or structural professional about waterproofing details.
Frequently Asked Questions
What's the difference between a lintel block and a steel angle lintel?
A lintel block (or bond beam block) is a concrete masonry unit with the top removed and filled with concrete and rebar to create a reinforced beam that matches the wall material. A steel angle lintel is a structural steel member (typically L-shaped in cross-section) that spans the opening and is embedded in mortar. Steel angles are stronger and shorter-span-friendly but require flashing for water management; lintel blocks integrate seamlessly with CMU walls but are limited in clear span.
Can I use a wooden beam as a lintel in a masonry wall?
Yes, wood beams (typically doubled or tripled 2×12s) are commonly used as lintels in masonry, especially for residential doors and windows, and are often the most economical choice. However, wood can rot if exposed to moisture, so it must be properly protected from water infiltration, and some codes restrict wood lintels in certain applications. Steel or concrete lintels are preferred in high-moisture areas or where long-term durability is critical.
How much bearing length does a lintel need on each side of the opening?
Building codes typically require 8–12 inches of bearing length (the horizontal distance the lintel rests on masonry) on each side of the opening, depending on lintel type, wall thickness, and load. Steel angle lintels often require 8 inches minimum; reinforced concrete bond beams and steel beams may require 12 inches or more for heavier loads. Always check your local code and structural drawings.
What happens if I use a lintel that's too small?
An undersized lintel will deflect (sag) under load, potentially cracking the masonry above it, damaging windows or doors, or allowing water to leak through cracks. In severe cases, the lintel can fail catastrophically, causing a localized collapse and creating a safety hazard. This is why proper calculation and code compliance are essential.
Do I need a structural engineer to design a lintel?
For standard residential openings (door and window widths up to 12 feet), many jurisdictions allow code-compliant lintel selection without engineer involvement. However, for large openings, heavy loads, seismic or high-wind zones, or commercial buildings, a structural engineer's design is typically required and always recommended to ensure safety.
Sources
- International Building Code (IBC) — Masonry Construction and Lintels
- Concrete Masonry Association (CMA) — Lintel Design and Installation Guide
- American Concrete Institute (ACI) 530/530.1 — Building Code Requirements for Masonry Structures
- National Concrete Masonry Association (NCMA) — TEK Series Technical Notes on Lintels
- Steel Beam Institute — Standard Practices for Steel Lintels in Masonry