A brick arch is a timeless architectural feature that adds elegance, strength, and character to any structure, from garden walls and gateways to fireplaces and doorways. The graceful curve of an arch can transform a simple opening into a stunning focal point. Many aspiring builders and DIY enthusiasts admire these structures but are often intimidated by the perceived complexity of their construction.
However, learning how to build a brick arch is a project that is well within the reach of someone with basic masonry skills and a patient, methodical approach. The key to success lies in careful planning and the creation of a temporary support structure, or formwork. This guide will demystify the process, breaking it down into clear, easy-to-follow steps. You’ll learn the essential bricklaying techniques needed to create a beautiful and structurally sound arch that will stand for generations.
Why Building a Brick Arch is a Masterful Skill
Building a brick arch is more than just a construction task; it’s a way to connect with centuries of architectural history and craftsmanship. This skill allows you to add a unique, high-end feature to your home or garden that significantly enhances its value and curb appeal. Unlike simple lintels, arches distribute weight more effectively, creating a stronger and more durable opening. Mastering this technique provides immense personal satisfaction and equips you with advanced masonry skills that can be applied to a wide range of future projects, elevating your capabilities as a builder.
7 Step-by-Step Guide: How to Build a Brick Arch
Step 1: Design the Arch and Build the Formwork
The first and most critical step is to design your arch and construct the temporary support structure, known as the arch formwork or “former.” This wooden support will hold the bricks in place until the mortar has cured and the arch can support itself. Start by deciding on the shape of your arch—a simple semicircular (or Roman) arch is the easiest for beginners. Using plywood, draw the exact curve of your arch’s underside. Cut out two of these curved shapes and connect them with pieces of timber to create a sturdy, three-dimensional form that matches the width of your wall.
Step 2: Set Up the Supporting Pillars
Your arch needs two solid pillars or walls to rest on. These supports must be level, plumb, and strong enough to bear the weight of the arch. Build up the brickwork on both sides of the opening to the “springing line,” which is the point where the arch begins to curve upwards. Use a spirit level consistently to ensure the tops of both pillars are perfectly level with each other. Any discrepancy in height at this stage will result in a lopsided arch. Once the pillars are ready and the mortar has had time to set, you can place your wooden formwork on top.
Step 3: Position the Arch Formwork
Carefully place the wooden arch formwork on top of the two supporting pillars, centering it within the opening. The formwork must be level and securely supported from below with timber posts and wedges. These wedges will be important later, as they allow for the gradual and easy removal of the formwork once the arch is complete. Ensure the top surface of the formwork is flush with the front and back faces of your brick wall. A securely positioned form provides the stable base you need for precise bricklaying and is fundamental to learning how to build a brick arch.
Step 4: Begin Laying the Bricks (Voussoirs)
Now you can begin the bricklaying process. The wedge-shaped bricks that form the arch are called “voussoirs.” Start laying the bricks simultaneously from both sides of the arch, working your way up towards the center. This balanced approach ensures even weight distribution on the formwork. Apply a generous layer of mortar to the side of each brick before placing it firmly onto the formwork. The mortar joints between the bricks should be wedge-shaped—wider at the top and narrower at the bottom—to follow the curve of the arch.
Step 5: Use a String Line for Accurate Placement
To ensure your bricks are placed correctly and maintain a consistent curve, use a guide line. Hammer a nail into the center point at the base of your arch’s curve on the formwork. Tie a string to the nail, and use it as a rotating radius guide. As you lay each brick, hold the string line against its top and bottom corners to check that its alignment is perfect. This simple but effective technique helps you maintain the structural integrity and aesthetic perfection of the arch, preventing any flat spots or inconsistencies in the curve.
Step 6: Master the Mortar Application
Proper mortar application is crucial for the strength of the arch. The mortar not only bonds the bricks but also transfers the compressive forces between them. Use a standard mortar mix (typically one part cement to three or four parts sand). The consistency should be firm enough to hold the bricks in place without slumping. Apply enough mortar to ensure the joints are completely filled when the brick is pressed into place. This is a critical part of the process of knowing how to build a brick arch that will last. Any voids in the mortar joints can create weak points.
Step 7: Place the Keystone
The final, central brick at the very top of the arch is called the keystone. This is the most important brick, as it locks all the other voussoirs into position and completes the arch’s structure. The keystone should be a wedge-shaped brick that fits snugly into the final gap. Apply mortar to both sides of the keystone and carefully but firmly press it down into place from above. This action will compress the entire arch, transferring the weight outwards and downwards onto the supporting pillars. The placement of the keystone is a moment of triumph in your project.
Common Mistakes to Avoid
When constructing a brick arch, there are several common mistakes to avoid that can compromise the structure and appearance of your project. First, do not rush the curing process; disturbing the arch before the mortar has fully set can lead to instability and cracking. Another common error is inconsistent mortar application, which can weaken the bond between the bricks and result in uneven joints. Additionally, failing to properly align the bricks during placement can lead to a lopsided or uneven arch.
Ensure that the bricks are uniformly spaced and follow the intended design precisely. Finally, neglecting to use a temporary support, such as a wooden form, can cause the arch to collapse before the mortar has hardened. Taking care to avoid these mistakes will help ensure a strong, durable, and professional-looking brick arch.
Frequently Asked Questions
What Is the Easiest Type of Arch for a Beginner to Build?
The semicircular arch, also known as a Roman arch, is the most straightforward type for a beginner to build. Its perfectly round, half-circle shape is easy to draw and construct on the wooden formwork. Because the curve is consistent, the angles of the brick joints are easier to manage compared to more complex shapes like a segmental or gothic arch.
Do I Need Special Bricks to Build an Arch?
While you can buy special tapered bricks called “voussoirs” that are pre-shaped for building arches, you can also build a perfectly strong arch using standard rectangular bricks. The key is to create wedge-shaped mortar joints between the regular bricks. The mortar joints will be wider at the top (extrados) and narrower at the bottom (intrados) of the arch, which accommodates the curve.
How Long Should I Wait Before Removing the Wooden Formwork?
Patience is critical. You should wait for the mortar to cure completely, which typically takes a minimum of one week, but waiting two weeks is safer, especially in cooler or damp weather. Removing the formwork too early, before the mortar has reached its full compressive strength, will cause the arch to collapse. The arch is not self-supporting until the mortar is fully hardened.
What Is a Keystone and Why Is It Important?
The keystone is the final, wedge-shaped stone or brick placed at the apex (the very top) of the arch. It is the most important part of the structure because it locks all the other bricks (voussoirs) into position. When the keystone is inserted, it evenly distributes the weight and compressive forces of the arch outwards and downwards through the bricks to the supporting pillars, making the entire structure self-supporting.
How Do I Calculate the Number of Bricks Needed for My Arch?
To get a close estimate, first measure the total length of the arch’s curve on your formwork. Then, measure the width of one of your bricks plus the width of one intended mortar joint (e.g., brick width of 4 inches + mortar joint of 3/8 inch). Divide the total length of the arch’s curve by this combined measurement. This will give you a good approximation of the number of bricks you will need. It’s always wise to buy about 10% extra to account for cuts or mistakes.
Conclusion
Successfully learning how to build a brick arch is a testament to a builder’s patience, precision, and understanding of fundamental structural principles. While the process may seem complex, this guide has shown that by breaking it down into logical steps—from building a solid formwork to the triumphant placement of the keystone—it becomes an achievable and deeply satisfying project for any dedicated DIYer.
The moment you remove the supports and see your arch stand on its own is a truly rewarding experience. You will have created a lasting architectural feature that adds immense beauty and character to your property. Now that you have the knowledge, it’s time to take on the challenge and build a structure that will stand as a proud accomplishment for years to come.