How to Build a Professional Structural Brick Entryway Archway Like an Expert Mason

Building a structural brick archway over an entryway or garden opening is one of the ultimate tests of a mason's skill. Combining geometry, physics, and fine craftsmanship, an arch transfers downward gravity loads outward along the curve to its supports rather than straight down. In this comprehensive, step-by-step tutorial, you will learn how to design, support, cut, and lay a structurally sound jack or semicircular brick arch like a seasoned professional.

🛠️ Essential Tools and Materials

Before you mix your first batch of mortar, you must gather professional-grade masonry tools and premium materials. Using the right equipment ensures precise cuts, level courses, and a safe, load-bearing structure.

Materials List

Tool Checklist

• Masonry Trowel (10 to 11-inch London pattern)
• Mason's Hammer and Chisel for splitting bricks
• Wet Tile Saw with Diamond Blade for precision wedge cuts
• Brick Jointer (half-round or barrel style)
• Builders Level (2-foot and 4-foot lengths)
• Framing Square and Compass for layout
• Safety Gear: Safety glasses, heavy-duty work gloves, and dust mask

📐 Planning, Geometry, and Layout

Every successful masonry arch begins on the drawing board. A semicircular arch requires precise calculations regarding radius, span, and rise.

Calculating Arch Dimensions

• Span: The clear horizontal distance between the two supporting jamb piers. For our project, we will use a span of 36 inches (914 mm).
• Rise: The vertical distance from the springing line (where the curve begins) to the highest point of the intrados (underside of the arch). For a true semicircle, the rise is exactly half the span: 18 inches (457 mm).
• Springline: The horizontal line where the vertical jamb ends and the curved arch begins.

🪵 Constructing the Wooden Centering Form

Because an arch relies on its final keystone to lock all the bricks in place under compression, the entire assembly must be supported from underneath until the mortar cures completely. This temporary wooden support is called centering or falsework.

Step-by-Step Centering Build

1. Cut the Arch Ribs: Using your 3/4 inch (19 mm) plywood and a pencil tied to a string acting as a compass, draw a semicircle with a radius of 18 inches (457 mm). Cut out two identical semicircular ribs using a jigsaw.
2. Build the Frame: Cut 2x4 lumber pieces to act as cross-braces connecting the two plywood ribs, spacing them roughly 4 inches (100 mm) apart around the perimeter.
3. Attach Flexible Hardboard: Screw a thin strip of hardboard or bending plywood (1/4 inch / 6 mm thick) over the curved perimeter of the wooden ribs to create a smooth, continuous curved surface for the bricks to rest upon.
4. Support Assembly: Mount the finished centering form securely between your two vertical brick jambs at the exact springline height. Use adjustable steel props or wooden wedges underneath so you can easily lower (strike) the form once the mortar cures.

🧱 Building the Supporting Jambs and Skewbacks

Before laying the arch itself, you must construct the structural vertical brick piers (jambs) on either side of the opening up to the springline.

Laying the Piers

• Mix your Type S mortar to a buttery consistency that holds its shape on the trowel without sliding off.
• Lay your bricks in a running bond, checking constantly with a 4-foot builder's level to ensure absolute vertical plumb.
• Stop building the piers precisely at the springline.

Preparing the Skewbacks

• The skewback is the angled masonry surface upon which the first arch bricks (springers) rest. The angle of the skewback must be perfectly perpendicular to the angle of the arch thrust.
• For a semicircular arch, draw a radial line from the center point of your arch circle to the outer edge of the springer brick. Cut your starting bricks or form the mortar bed to match this exact radial angle (typically pointing toward the center point of the arch circle).

🏗️ Laying the Arch Ring and Keystone

With the centering firmly in place and skewbacks prepared, you are ready to lay the voussoirs (the wedge-shaped bricks forming the arch ring).

The Golden Rules of Arch Laying

1. Work from Both Sides Simultaneously: Lay bricks symmetrically, starting from the left skewback and the right skewback at the exact same time. This balances the lateral loads on your wooden centering form and prevents the form from shifting.
2. Maintain Tapered Mortar Joints: Brick arches require tapered mortar joints. The joint must be thinner at the inner curve (intrados) and wider at the outer curve (extrados). Use plastic tile spacers or thin wooden shims if necessary to maintain consistent joint spacing (ideally 3/8 inch or 10 mm at the extrados).
3. Cut Wedge Bricks (Voussoirs): Standard rectangular bricks will not work without excessively wide mortar joints at the top. Use your wet tile saw to cut your arch bricks into tapered wedges matching the radial lines of your layout.
4. Drive the Keystone: As you approach the top center, leave just enough space for one final brick: the keystone. Coat all sides of the keystone liberally with mortar and drive it downward gently into the central slot using a rubber mallet. This locks the entire arch in full structural compression.

🧹 Finishing, Joint Tooling, and Curing

Once the keystone is locked in place, your arch is structurally self-supporting, but proper finishing and curing ensure long-term durability against weather and moisture.

Joint Tooling and Cleaning

• Allow the mortar to set up to a thumbprint-hard consistency (usually 1 to 2 hours after laying).
• Use a half-round masonry jointer to compact and smooth every mortar joint. This compresses the mortar, sealing out moisture and giving a clean, professional aesthetic.
• Immediately brush away excess mortar crumbs using a soft-bristled brush. Wipe down the entire brick surface with a dry sponge or burlap sack to remove mortar smudges.

Curing the Masonry

• Mist the arch gently with clean water once a day for 3 days. Proper moisture retention allows the hydraulic cement in Type S mortar to achieve its maximum compressive strength.
• Striking the Centering: Leave the wooden centering form in place for a minimum of 7 full days in warm weather (or 14 days in damp, cool weather) before gently releasing the wedges and lowering the formwork.

📋 Troubleshooting Common Arch Issues

🎉 Conclusion and Maintenance

Congratulations! You have successfully designed, built, and set a professional structural brick entryway archway. By respecting the physics of compression, maintaining precise geometric layout, and utilizing proper wooden centering, you have created a permanent architectural feature that will stand strong for generations.

To maintain your new masonry arch, inspect the mortar joints annually. Apply a breathable, siloxane-based masonry sealer every 3 to 5 years to protect the clay brick and mortar from freeze-thaw spalling and efflorescence.