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I design brick arches and cast stone using simple geometry and AutoCAD. We cut brick shapes and then prefabricate traditional masonry arches that stand the test of time. I want to share the mathematical formulas of arch building. by Justin Wethington

Ft. Myer

By Justin Wethington, Apr 18 2016 01:52PM

I had never heard of Ft. Myer before Randy of LDC masonry called me to talk about a building he is renovating there. The base is nestled right next to Arlington National Cemetery. We met across from the chapel on base at 8 am a few days before veterans day. I was waiting in my truck for Randy to arrive while I watched a military funeral procession happening in front of the chapel. I felt a deep sense of gratitude for the life I have as I watched the funeral of some anonymous soldier. The army funeral rituals were so deliberate and sorrowful. I was moved by the immense size of Arlington Cemetery and I felt heavyhearted the rest of the day.

The arches we were trying to match were made of standard size brick and are 8 brick courses tall. They arch is double wythe with a 3" rise in the center.

I designed the arch radially so that the bed joints will not be horizontal but would correspond with the 3" center rise. This also keeps the bonded soffit effect of the arch and keeps all the small pieces at the top of the arch.

The resulting arch has a 75 degree skew back angle. This is structurally sound and self supporting because the width at the top of the jack arch is 56" and the masonry opening is 44.625". There is some simple geometry involved in designing a radial arch out of brick. The key is to maximize the thickness of the 2.25" brick. If we have a masonry opening and rise in inches we can get the radius...if we have the radius we can get the circumference(2πr)...Take the circ x ANG divided by 360 = length of arc. When you have the length of the arch in inches you can determine bond, brick size and joint angle.

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