How to Make a Lintel Opening in an Existing Concrete Block Wall

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If you want to create an opening for a new door in an exterior wall, it may seem like a straightforward process: Just knock out the appropriate amount of space, place the new door frame in the hole and clean it up so everything looks nice. In truth, this should never be attempted because you may be damaging a load-bearing wall in the process, which could lead to extensive damage to the building or, if things go dramatically wrong, people getting hurt or even killed. Especially when dealing with brick and concrete block walls, the installation of a lintel is required before opening up the load-bearing wall. While installing a lintel in a block wall isn't a difficult process if you have a moderate amount of masonry experience, it still requires care, close attention and a number of safety procedures.

How to Make a Lintel Opening in an Existing Concrete Block Wall
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A Sturdy Cinder Block Lintel

A lintel – sometimes referred to as an RSJ, H-beam, I-beam or double T-beam – is a type of support beam. Available in a variety of materials including wood, stone and concrete, most modern buildings use flat steel lintels. Installed into a load-bearing wall, a lintel redirects the load of the wall away from the material below it and into the building's foundation, allowing for the construction of new openings in the wall without risking critical damage to the entire building. In structures built from brick, concrete or cinder block, the lintel is placed into the mortar between layers of the material.

Lintels are easily available from most construction material manufacturers and large hardware stores, and though they aren't terribly difficult to install, you should not attempt to install a lintel into your wall without taking the appropriate precautions. Check with your local governing office to ensure that your construction plan is legal, and consult a structural engineer or credible builder before proceeding. They will be able to tell you where a lintel can and should be placed as well as what material will be required for that lintel. Lintels must always be at least 300 millimeters longer than the gap they sit over, so the expert will likely give you the exact measurements required of your new lintel.

Opening the Mortar

Once you've consulted an engineer or builder and received approval for your construction project, you can begin the lintel installation process. If you lack masonry experience, it is advisable to call a professional to complete the rest of this process in order to minimize the potential risk. Steel lintels in concrete block walls are placed in the mortar between blocks, so the first step will be opening a space for the lintel itself. With the intended position of the lintel marked on the wall, carefully use an angle grinder or masonry saw to cut away the mortar. Grind down parts of the concrete blocks if necessary, and then use a hammer and chisel to knock away anything remaining. Use a hammer drill with a 10-millimeter masonry bit to clean up the gap in the wall so the lintel can be smoothly inserted.

Steel Lintel Installation

Once the space for the lintel is open, set it inside the gap and use a sledgehammer to gently knock it into place, making sure it is snug but without damaging any of the surrounding wall. You may then secure the lintel by preparing and applying ready-mix mortar to the area around the lintel. Smooth the mortar to match the rest of the wall if necessary, and your lintel will be installed.


Blake Flournoy is a writer, reporter, and researcher based out of Baltimore, MD. As a handyman's apprentice operating out of the Atlanta suburbs, they made a name for themselves repairing appliances and installing home decor. They have never seen Seinfeld and are deathly scared of wasps.

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