Print Friendly, PDF & Email
The inside of the baptistery, where people were baptized

Arches of the Medieval Baptistry at Pisa

How do you hold up the roof?

People building houses or any other kind of people have always had this one big problem, which you may have had also if you ever tried to build a clubhouse: how do you get the roof to stay up?

History of houses
Roman architecture

a drawing of a flat roof over two walls

A flat roof

A flat roof will work

How do you build the part of the wall over the door or the window? One way (the way people figured out first) is to have a long piece of wood or stone that goes over the whole way from one wall to the other, like the picture here. That works (though it’s harder than it looks to get the walls to stay up with the roof on.) And many people did build their houses and tombs and temples that way in the Stone Age and the Bronze Age.

Indian temples with flat roofs

A gabled roof

A gabled roof

Or a gabled roof

But if you want to make a big building, you need very long beams to make a flat roof like this. And there are not very many big trees in the Mediterranean, so it is very hard to get so many long beams. One thing that helps is to make slanted roofs (gabled roofs), which is what most Greek temples have. But you still need a lot of expensive long beams.

Greek temples with gabled roofs
Han Chinese watchtowers

An arch with a keystone

An arch with a keystone

But the arch is a cheaper way

The arch is another way to solve this problem. It’s a way of making a roof or a doorway or a window without using any beams at all: just a lot of small stones, or small blocks of wood, or clay bricks. That’s a lot cheaper and easier to get than the big beams. You use the weight of the blocks to hold the arch together.

A long arch is a barrel vault
More about groin vaults
An arch spins around to be a dome

Who invented arches?

The aqueduct at Nimes, in southern France (Pont du Gard)

The aqueduct at Nimes, in southern France (Pont du Gard)

People have used arches since the Bronze Age in tombs and sewers, but Roman architects were the first to use arches a lot in their public buildings. Arches are important in Roman aqueducts, Roman basilicas, and Roman amphitheaters, for example.

More about aqueducts
The Basilica of Maxentius
Triumphal arches
Roman amphitheaters
What’s a vomitorium?

Parthian arches

Arch of Sapor - Parthians

Arch of Sapor – Parthians

Not much later, Parthian architects in Iraq and Iran started to use a lot of arches in their buildings too. Sassanian architects also used a lot of arches.

Parthian architecture

Medieval arches

Later buildings in the Islamic Empire and in medieval Europe, like mosques and palaces and cathedrals, also used a lot of arches.

Cordoba mosque

Cordoba mosque

Fatimid architecture
Islamic mosques
Kairouan mosque
Medieval architecture

Make your own arch

You can try this yourself if you get a set of arch-building blocks. Or cut them yourself out of wood. Try it with Legos. You lay the arch out on a board laid flat on the floor, and then tilt it up slowly and see if it holds.

Project on arches

A long arch is a barrel vault
More about groin vaults
An arch spins around to be a dome

Bibliography and further reading about arches and architecture:

Arches to Zigzags: An Architecture ABC, by Michael J. Crosbie (2000). Shows what an arch is, or a gable, or an eave.

Eyewitness: Building, by Philip Wilkinson, Dave King, and Geoff Dann (2000). Lavishly illustrated, like other Eyewitness books, and with good explanations of most architectural terms.

City: A Story of Roman Planning and Construction, by David Macaulay (1983).

What’s a barrel vault?
What’s a dome? home