The art of construction of stone unit bonded together with mortar is called stone masonry.
Stone-masonry is used in building foundation, retaining walls, arches, floors, walls & columns. Mostly natural rocks are used in stone masonry. Natural rocks are cut and dressed into proper shape before using. Stone-masonry is very strong & durable. The strength mainly depends upon the types of stones or the mortar used.
Materials Used in Stone Masonry
Materials used in stone masonry are:
Stones to be used in stone masonry should be hard, durable, tough and free from cavities, sand holes & cracks.
Selection of stones should be done based on the availability of stones and the importance of structure. Limestone, sandstone, granite, marble, laterite, etc are the commonly used stones in masonry.
Cement and lime mortar are commonly used in this masonry. Selection of mortar depends upon the strength required, the colour of stone and loads coming on the structure.
General Principle in Stone Masonry:
The following point should be considered while supervising the stone masonry.
– The stone used should be strong, tough, hard and free from cracks and cavities.
– Each stone should be well-wetted before use so that it does not absorb water of mortar.
– The stone should be dressed properly according to types of masonry.
– Masonry works should be raised uniformly.
– Broken stones should not be used for facing and backing.
– Wall should be laid completely vertical.
– If stone masonry is to carried out at a higher level, double scaffolding should be used.
– No tensile stress should be produced anywhere because a stone is weak in tensile strength etc.
Tools used in Stone Masonry
Some common tools used in the stone masonry are:
a. Spalling Hammer
d. Iron Hammer
f. Claw Tool
j. Pitching Tool
Types of Stone Masonry
1) Rubble masonry:
In this masonry, the stone of irregular shape and size are used which are taken from quarrying. The strength of rubble masonry mainly depends upon the quality of the mortar used. The thickness of the joints is not uniform. This masonry is cheaper as it doesn’t require dressed stones. It is suitable for light and temporary structures.
a. Random Rubble Masonry
Masonry constructed using undressed or partially dressed stones in a random order is called Random Rubble Masonry. There are 2- types of random rubble masonry:
1. Un-coursed Random Rubble Masonry
The random rubble masonry constructed without forming courses is Uncoursed Random Rubble Masonry. It is mostly used for the construction of walls with a low height.
Some of the features of this masonry are:
a. It is the cheapest and roughest type of masonry.
b. It has varying appearance.
c. Corners of stones are slightly knocked off before using.
d. To increase the strength of this masonry, large stones are used at corners and jambs.
e. “Through stone” is used in every square meter for joining faces and backing.
2. Coursed Random Rubble Masonry
The masonry in which stones are laid in courses & layers of equal height is called Coursed Random Rubble Masonry. It is used in the construction of go-downs, boundary walls, etc. Commonly hammer dressed stones are used in this masonry.
b. Squared Rubble Masonry
The type of rubble masonry in which face stones are squared on all joints and beds by dressing before laying is called Square Rubble Masonry.
There are 2 types of square rubble masonry which are explained below:
a. Coursed Square Rubble Masonry
The square rubble masonry in which stones are laid in courses is Coursed Square Rubble Masonry. It is used for the construction of hospitals, schools, markets, modern residential buildings etc. It is also used in hilly areas where the availability of quality stones is common.
Some features of this masonry are:
a. It is a superior variety of rubble masonry.
b. Stones used are squared on all joints and beds and laid in courses.
c. Stones are laid in courses of equal layers.
d. Joints are uniform.
b. Un-Coursed Square Rubble Masonry
The square masonry in which stones are laid without making courses is called Un-coursed Square Rubble Masonry.
It is mostly used in the construction of ordinary buildings in the hilly areas where the availability of quality stones at cheap rate is common.
c. Dry Rubble Masonry
The rubble masonry constructed without using mortar or other binding agents is called Dry Rubble Masonry. Un-dressed or partially dressed stones are used in this masonry.
It is suitable for constructing the walls of height less than 6 m.
2) Ashlar Masonry
The stone masonry constructed using finely dressed stones is called ashlar masonry. Some features of ashlar masonry are:
a. The courses are of uniform height.
b. All the joints of this masonry are regular, thin and have a uniform thickness
c. Ashlar masonry is mostly used in the construction of heavy structures, architectural buildings, high piers and abutments of bridges.
There are 5 types of ashlar masonry. They are:
a. Ashlar Fine or Coursed Ashlar Masonry
~ In this masonry, finely dressed stones having uniform size & almost rectangular in shape are used.
~ It is very costly.
~ Wastage of material while dressing is high and also requires many labours for the dressing process.
~ Desired bond can be obtained easily in this masonry.
b. Ashlar Rough Tooled Masonry
~ The beds and sides are finely dressed using chisels but the face is made rough.
~ A 25 mm wide strip made using chisels is provided around the perimeter of the rough dressed face of each stone.
~ The thickness of joints is always uniform, which is always less than 6 mm.
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c. Rock or Quarry Faced Ashlar Masonry:
~ It is similar to ashlar rough tooled masonry except that there is chisel-drafted margin-left rough on the face which is known as quarry faced.
d. Chamfered Ashlar Masonry:
~ It is similar to Rock or Quarry Faced Ashlar Masonry but it is bevelled or chamfered at an angle of 45° for the depth of 2.5 cm or more.
e. Ashlar Back in Course Masonry
~ It is the combination of rubble and ashlar masonry.
~ It is also called ashlar facing.
~ In this, facing work is done using finely dressed stones and backing work is done using rough stones.
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