Basics in Building Construction

Building Components And Types

Lesson 17 and 18 : Arches

Classification Based On Material And Workmanship

Stone Arches

Depending upon workmanship, stone arches are of two types: (i) Rubble arches, and (ii) Ashlar arches.

1. Rubble Arch



Rubble masonry arch is comparatively weak and is used for comparatively inferior work. These arches are made of rubble stones which are hammer dressed, roughly to shape and size of voussoirs of the arch and fixed in cement mortar. Rubble arches are used upto spans of 1 m. They are also used as relieving arches, over wooden lintels. Upto a depth of 37.5 cm, these arches are constructed in one ring. For greater depths (thickness), rubble stones are laid in two rings in alternate course of headers and stretchers.

2. Ashlar Arch

In this type, the stones are cut to proper shape of voussoirs, and are fully dressed, set in lime or cement joints with proper bed joints. Up to depth of 60 cm, the voussoirs are made of full thickness of the arch. For determining the wedged shapes of voussoirs, it is preferable to set out the arch on a level platform, marking on it the key-stone and voussoirs along with radial mortar joints. Ashlar stone can also be used to make flat arches, in which the joints are either joggled or rebated.