The segmental arch describes a segment of a circle and has all the same basic features as the flat arch except that the curved extrados and intrados radiate from the same focal point. Measure the face height along any long joint line radiating from soffit to head.
The segmental arch may feature a profiled hood around the extrados called the label course which often projects from the face brickwork. This feature is often used as a weathering over an opening and can sometimes have a lead work dressing over.
The graphic shows an example of a Bulmer fabricated structural arch. The animated video demonstrates the simple construction process.
To specify a segmental arch you will need the following information. When measuring period property it is useful to measure the work, using the system in which it was built. Typically, before 1970 in the UK work was built using Imperial dimensions E.g. 4 courses per foot or in metric, 4 course per 305mm:
- Brick type & colour
- A digital image of similar arches on the property in nearby
- Opening span
- Camber rise to the centre of the arch at the soffit. Typically a fixed number of full courses, (measured at the centre from the lowest points of the arch).
- Face height, (measured along any long joint line radiating from soffit to head)
- Joint width
- Number of voussoirs (complete tapered sections from Intrados up to Extrados counted across the arch).
- Bond pattern, (the horizontal joint pattern across the arch)
- Soffit depth (from front to back)
- Brick finish (rubbed or sand faced)
We will also need to know whether the arch will have any special features such as a keystone or carved soffit. If you are not sure call us on 01787 269132 for advice or email your enquiry to email@example.com
Note: The radius of the arc, (the distance from the intrados to the focus), can be calculated from span and camber rise.