Stone Masonry and Types

Stone is hard non-metallic mineral matter of which rock is made of. It has no definite shape but it is mixture of two or more minerals bonded together. It has been used for construction since ancient time. Masonry is building of structures from individual units which are often laid and bound together using mortar. So when the stone is used as a unit with other materials as mortar then it is called stone masonry.

Types of stone masonry:

A) Rubble Masonry:

In Rubble masonry the stones used are either undressed or comparatively roughly dressed. The masonry has wide joints since stones of irregular shapes are used.

i)                    Random rubble

a.       Un-coursed(Random Rubble)

It is the roughest and the cheapest form of stone walling. Since stones are not uniform shape and size, they are arranged with great care so as to distribute pressure over maximum area and at the same time avoid long vertical joints.

b.       Built to course(Coursed Rubble)

It is similar to un-coursed except that the work is roughly levelled up to form courses 30-45 cm thick and not less than 15 cm.

ii)                  Square rubble

a.       Un-coursed

Stones having straight beds and sides are arranged in irregular pattern to give good appearance and avoid the formation of long, continuous joints.

b.       Built to Course

Stones having straight bed and sides are levelled up to form courses of varying depth.

c.       Regular Course

Stones having straight beds and sides are levelled up to form courses of varying depth but the height of stones in each course, is the same.

iii)                Miscellaneous type

a.       Polygonal rubble masonry

In this type, stone is hammer finished on face to an irregular polygonal shape. If stones are roughly shaped to form rough fitting, such a work is called rough picked form and if they are carefully shaped to form close fitting then it is called close-picked form.

b.       Flint rubble masonry

In this type, flints or cobbles which vary in width and thickness from 7.5 cm to 15 cm and length from 15 cm to 30 cm are used. The stones are extremely hard but brittle. Strength of such walls can be increased using lacing course of thing long stones or bricks at 1 to 2 m vertical intervals.

iv)                Dry rubble masonry

In this masonry, mortar is not used in the joints, so it is the cheapest but requires more skill in construction. It is mostly used for non-load bearing walls like compound walls.

B) Ashlar Masonry:

In this masonry, square or rectangular blocks that are used are dressed and have extremely fine bed and end joints.

i)                    Ashlar fine tooled

It is the finest stone masonry. The bed, joints and faces of the stones are chisel dressed to remove all unevenness and obtain perfectly horizontal and vertical joints.

ii)                  Ashlar rough tooled
                                          

The beds and sides are finely chisel dressed but the exposed face is dressed by rough tooling.

iii)               Ashlar rock faced
                                          

The exposed face of the stones is not dressed but is kept as such to give rough facing.

iv)                Ashlar chamfered
                                          

It is special type of ashlar rock faced in which the strip provided around the perimeter of the exposed face is chamfered at an angle of 45 degree to a depth of 25 mm.

v)                  Ashlar block in course
                                          

It is an intermediate between ashlar and rubble masonry. Faces of each stone are hammer dressed but the vertical joints are not as straight and fine as in ashlar masonry.

vi)                Ashlar facing
                                        

It is provided along with brick or concrete block to give better appearance. The exposed faces of the stone are rough tooled and chamfered.