A shape that tapers in thickness from one long edge to the other, so that with the 4.5-inch face running through the arch it turns a curve. Arch brick builds sprung arches and rings about 4.5 inches thick, and is numbered No. 1 to No. 4 in order of increasing taper and tighter radius. Mixing two numbers in the right ratio gives any radius between them, which is the basis of arch brick tables.
Ring needs a mix of No. 1 and No. 2 arch brick, run the radius through the tables before we order.
Arch tables give the count of each shape per ring for a given radius; using them saves a pile of cut closers.
Also heard as
- arch
- side arch
- No. 1 arch
Do not mix it up with
- Wedge brick: Arch brick tapers across its width for arches about 4.5 inches thick; wedge brick tapers along its length for arches 9 inches and thicker.
Related terms
Wedge brick
Brick whose thickness tapers along its length, used for arches and rings 9 inches or more thick.
Key
The last brick driven into an arch or ring to lock it tight, or a shape that tapers in width for turning circles.
Skewback
Angled brick or support course from which a sprung arch springs and pushes its thrust into the steelwork.
Straight
The standard rectangular firebrick, 9 by 4.5 by 2.5 inches in US sizing, used as the counting unit for brickwork.