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If you put a hole in a masonry wall and step on the top of it, you're apt to find yourself on the ground below pretty
fast. However, if you distort the individual stone shapes to where they're larger at the top than at the bottom, they'll hold
you up because they'll act like the stopper in a bottle..
If you Google arch types, you'll find a more sophisticated definition, but that's how it works. These stones are
known as voussoirs, and the one in the middle is the key or keystone, which
now makes sense to me. It's also called the capstone. Some examples.
The abutments of an arch are located at either side of it, and the span is measured
horizontally from abutment to abutment. Its vertical measurement is called the rise.
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| Jack or Flat Arch |
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| Round or Roman Arch |
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This arch is made up of an odd number of voussoirs.
It's found in styles such as Italianate, Italian Renaissance, Romanesque, Richardsonian, Spanish Eclectic, and Spanish
Colonial.
The curved top is called the extrados, while the lower curve is known as the intrados.
If the lower line of an arch is a surface, it's called a soffit.
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The rise of an arch is measured from the highest point of the arch to where it starts.
While the Roman arch forms a semicircle, this round arch has a partial curve.
Found in Italianate and Colonial styles.
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| Segmental Arch |
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| Triangular Arch |
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What happens when you take a triangular arch and a rounded arch and put the shapes together?
Look at the Gothic arch below.
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Also known as a drop, equilateral or lancet arch, depending on if
the spacings of the centers are respectively less than, equal to, or more than the clear span, which is the horizontal clear
dimension between abutments (The masonry or combination of masonry and other structural members which support one end of the
arch at the skewback.)
The surface on which the arch joins the supporting abutment is the skewback. Whew. That was a mouthful.
These are almost always found in the Gothic Revival style.
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| Pointed or Gothic or Ogive Arch |
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| Tudor Arch |
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If you distort a Gothic arch, you get the Tudor, found in Gothic Revival and Tudor Revival styles.
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Found in the Moorish Revival style. Mostly seen in commercial buildings and used primarily for decoration.
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| Horseshoe or Moorish Arch |
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| Multicentered Arch |
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Also known as basket or basket handle. The center is not a circle, but rather fashioned
from a number of arcs. Its width is much greater than its height.
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An arch used over the triple opening of the so-called Venetian or Palladian window, flat over the narrow
side lights, round over the larger central opening.
However, when the Venetian arch is known as an ogee or keel arch, it is formed
from two S-shaped forms on either side.
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| Venetian or Queen Anne Arch |
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| Bullseye or Circular Arch |
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Decorative. Often used in the Orient.
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Arches frame and support doors, windows, porches, and other wall openings including fireplaces. You can see how strong
they are because those built hundreds of years ago still stand.
A blind arch is one in which the opening is filled with masonry.
Arches can intersect, leading to spectacular design possibilities through the ages. Put two arches together, and the structure
is even stronger.
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| Vault |
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