Classification or types of Stone Masonry

 Classification of Stone Masonry

These are two types and

Rubble and Ashlar masonry are of the following types

1. Rubble Masonry

In this type of masonry, stones of irregular sizes are used. The stones are obtained from quarry are taken to be used in the same form or are broken and shaped into suitable sizes by means of hammer as the work proceeds.

The strength of rubble masonry depends upon

1. The quality of mortar

2. The proper filling of the mortar between the spaces of the stones.

3. The use of the long stones at frequent interval for proper bonding.

a. Coursed rubble masonry

In this type of rubble masonry the heights of stones vary from 20 to 50mm. This type of masonry is used for the construction of public and residential buildings. 

Also coursed rubble masonry divided into 3 types

1. Coursed rubble masonry I sort: In this type stones of the same height are used and the courses are the same heights. The thickness of the mortar joint does not exceed 10mm.

2. Coursed rubble masonry II sort: The stones to be used are of different heights. The courses need not to be of equal height. The thickness of mortar joint is 12mm. 

Only two stones are used to mak eup the height of one course equal.

3. Coursed rubble masonry III sort: The stones to be used of different heights the minimum being 50mm. The courses need not be equal height. The thickness of the mortar joint is 16mm.

Only three stones are to be used to make up the height of one course equal.

b. Uncoursed rubble masonry

In this type of masonry the stones are not dressed. The courses are not maintained regularly. The larger stones are laid first the spaces between them and then filled with spalls. 

This type of rubble masonry being cheaper is used for the construction of compound walls, gargages, labour quarters.

c. Random rubble masonry

In this type of masonry stones of irregular sizes and shapes are used. The stones are arranged of good appearance. More skill is required to make the masonry structurally stable. 

Two types

1. If the face stones are chiesel dressed and the thickness of mortar joints does not exceed 6mm it is known as random rubble masonry I

sort.

2. If the face stones are hammer dressed and the thickness of mortar joints does not exceed 12mm it is known as random rubble masonry II sort.

This type of building is used for the construction of residential building.

d. Dry rubble masonry

This is just similar in construction to the coursed rubble masonry III sort except that no mrtar is used in the joints.This type of masonry is cheapest but required more skill.

It is most used in compound walls, pitching on bridge approches, retaining walls  etc.

e. Polygonal rubble masonry

In this type of masonry the stones are hammer dressed and the stones selected for face work are dressed is an irregular polygon shape. Thus the face joints are seen running in an irregular shapes in all directions. 

More skill is required.

f. Flint rubble masonry

In this type of masonry the stones are used as flints that are irregularly shaped nodules of silica.

 The width and thickness vary from 80mm to 15mm  and the length vary from 15mm to 30mm.

2. Ashlar masonry

This type of masonry built from accurately dressed stones with uniform and very fine joints of about 3mm thickness. By arranging the stone blocks by varies patterns different types of appearances can be formed. 

The backing of ashlar masonry walls may be built af rubble or ashlar masonry.

a. Ashlar fine masonry

This is the finest type of stone masonry work. Each stone is cut to regular and required size and shape so as to have all sides rectangular, so that the stone gives perfectly horizontal and vertical joints with adjoining stone. 

The size of the stone to be laid in regular courses should not be less than 300mm in height. The width of the stone should not be less than the height of the course.

Generally face stones are laid as header and stretchers alternatively. The headers comes under the middle portion of the stretcher. In order to break the continous vertical joints the stones in the adjacent layers should have a lap of more than half of the height of the course.

All the joints should be made of mortar with a maximum thickness 3mm.

b. Aslar rough tooled

The exposed faces of this type of masonry should be given a fine dressed chiesel drafting of about 25mm width. 

In between the drafts portion should be roughly tooled. The joint thickness should be 6mm.

c. Ashlar rock or quarry faced

In this type of masonry the exposed face of the stone is not dressed but kept as such so to give rock facing. A strip of about 25mm wide, made by means of chiesel is provided around the perimeter of the exposed face of every stone. However the projection of size more than 8cm are broken.

All other specification regarding the size of the stone and the bond are kept similar to ashlar rough tooled masonry.

d. Ashlar chamfered

This is special form of rock-faced ashlar masonry in which the strip provided around the perimeter of the exposed face in chamfered or bevelled at an angle 45°by means of chisel to a depth of 25mm. 

Due to this a groove is formed in between adjacent block of stones. Around this bevelled strip another strip of 15cm is dressed with the help of chisel.

e. Ashlar block in course masonry

This type of masonry occupies an intermediate position between the rubble and ashlar masonry. The faces of stones are generally hammer dressed and the thickness of mortar joints does not exceed 6mm. 

The depth of course varies from 20 to 30cm. This type of construction is used for heavy engineering works.