Stone Masonry

STONE MASONRY

Stone masonry is used for the construction of walls, columns, lintels, arches, beams, etc., of a building. Stones are abundantly available in nature and when cut and dressed to proper shapes, they provide an economical material for the construction of various parts of building. Stone masonry can be classified according to the thickness of joints, continuity of courses and finish of face.

TYPES OF STONE MASONRY

Stone masonry is divided into various types as shown below:

RUBBLE MASONRY

In this type of masonry stones employed are either undressed or roughly dressed. These masonry constructions do not have a uniform thickness. The strength of the rubble masonry is dependent on the quality of mortar used, use of long through stones, and proper filling of mortar between the stone spaces and joints: Rubble masonry can be again classified into the following types:

❖ Coursed Rubble Masonry: In this type of masonry, the stones in a particular course are of equal heights. The stones hence used possess different sizes. Also in this type, all the courses do not have same height. This type is commonly employed in the construction of public buildings, abutments, residential buildings and piers of ordinary bridges.

❖ Uncoursed Rubble Masonry: This type of rubble masonry is the cheapest and roughest form of stone masonry construction. This masonry use stones of varied shape and size. The undressed stone blocks which are directly taken from the quarry are used. The courses are not maintained regularly in this method of construction. Initially larger stones are laid first. The spaces between them are filled with spalls or sneeks. These are further divided into random uncoursed and square uncoursed.

Random Uncoursed Rubble Masonry: In this type, the weak corners and edges of the stone are removed with the help of a mason's hammer. At the quoins and jambs, bigger stones are employed in order to increase the strength of the masonry.

❖ Square Uncoursed Rubble Masonry: In this type, the stones are made roughly square shape and used in construction. The facing stones are provided a hammer-dressed finish. Larger stones are used as quoins. Here chips are not used as bedding.

❖ Dry Rubble Masonry: These are rubble masonry construction performed without the use of mortar. Small spaces are filled with smaller stone. pieces. It is used in pitching the earthen dams and the canal slopes.

❖ Polygonal Rubble Masonry: In this type, the stones used for masonry are roughly shaped into irregular polygons. The stones are then arranged in such a way that it avoids vertical joints in the face work. Also stone chips are used to support the stones.

❖ Flint Rubble Masonry: In areas where flint is available plenty, a flint rubble masonry is employed. Flints are irregularly shaped nodules of silica. They are extremely hard but brittle in nature. The thickness of the flint stones varies from 8 to 15cm. Their length varies from 15 to 30 cm.

ASHLAR MASONRY

Ashlar masonry is constructed using accurately dressed stones that possess uniform and fine joints. The thickness of the joints ranges about 3mm which is arranged in various patterns. The size of the stone blocks must be in proportion with the thickness of the walls. The various types of ashlar masonry are:

❖ Ashlar Fine Masonry: In ashlar fine masonry construction, each stone is cut into uniform size and shape, almost rectangular in shape. This shape hence provides perfect horizontal and vertical joints with the adjacent stones. An ashlar fine masonry construction is very costly.

❖ Ashlar Rough Masonry: This type has stones whose sides are finely chisel -dressed. The face of the stones is made rough by means of tools. Around the perimeter of the rough dressed face of each stone, a strip of 25mm width is provided.

❖ Rock and Quarry Faced: This masonry type has a 25 mm wide strip made by a chisel placed around the perimeter of every stone. The remaining portion of the face is left in the same form as it is received.

❖ Ashlar Block in Course Masonry: This type is a combination of ashlar masonry and rubble masonry. The faces work of the masonry stones is either rough tooled or hammer dressed stones. The backing of the wall may be done in rubble masonry.

❖ Ashlar Chamfered Masonry: A strip is provided as shown in the figure. Sides of the stones are chamfered or beveled at an angle of 45 degrees by means of a chisel at a depth of 25mm.