What is a pointed arch?
A pointed arch is an arch made up of two circular segments that meet at a point at the top. The centres of the two arcs lie side by side on the springing line (the line from which the arch starts), or outside it. The pointed arch is the characteristic arch type of Gothic architecture, the style that emerged in France from the 12th century and spread across Europe. You see it in windows, doors, vaults and arcades.
Forms
- Equilateral pointed arch. The radius of the arcs equals the span. The arch and springing line then form an equilateral triangle.
- Lancet arch. The radius is greater than the span; the arch is slender and tall.
- Depressed pointed arch. The radius is smaller than the span; the arch is lower and wider.
Structural advantages
- Height independent of width. In a round arch the height is always half the span. In a pointed arch you can choose the height. This means arches of different widths can still reach the same height, which solves a great deal in rib vaults.
- Less horizontal thrust. A pointed arch carries the load down more steeply than a round arch of the same width. The horizontal force on the supports is therefore smaller, although still present; that is why Gothic churches have buttresses and flying buttresses.
- Larger openings. Thanks to this more favourable load path, walls could become thinner and windows larger.
Application
- Repairing a historic arch. Survey the arch accurately and make a timber centring (former) on which to lay the bricks. Leave the centring in place until the mortar is strong enough.
- Made-to-measure frames. Pointed-arch frames are bespoke. Have the arch shape measured at several points, as old arches are often not exactly symmetrical.
- Keystone not first. Build up evenly from both springings and place the top stone last.
- Watch for cracks at the crown or shifted springings: these indicate supports that are spreading.
Common mistake: removing a buttress or wall section next to an arch during alterations. Without that counterweight, the arch can spread.
Related terms
- Gothic architecture
- Lancet arch
- Round arch
- Rib vault
- Buttress
- Flying buttress
- Tracery
- Horizontal thrust
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