Stone masonry is classified based on the thickness of joints, continuity of courses and finish of face. Rubble Masonry and Ashlar Masonry are discussed below (IS: 1597, Parts 1 and 2, 1992).
1. Rubble Masonry
Rubble masonry is a stonework wherein blocks of stones are either undressed or roughly dressed and have wider joints. The stones used are not of uniform size and shape but generally of pyramidal in shape to some extent. Vertical and transverse bonds have to be attained. Through stones are provided from back to the face of wall to ensure better bonding. The strength of this masonry depends on the quality of mortar, use of through stones and filling of spaces. There are different types of rubble masonry, viz., random rubble, squared rubble and polygonal rubble. Figure 16.7 shows the various types of rubble masonry.
Figure 16.7 Types of rubble masonry
2. Ashlar Masonry
Ashlar masonry is a stonework wherein blocks of stones are accurately dressed with very fine joints of 3 mm thickness. It is essential to ensure that the sizes of individual stones are in conformity with the general properties of the wall. In this masonry the beds, sides and faces are finely chisel dressed. The backing of such walls may be rubble or ashlar masonry. It is the highest grade of masonry and costly. There are different types of ashlar masonry, viz., ashlar fine, ashlar rough tooled, ashlar rock or quarry faced, ashlar chamfered and ashlar facing. Figure 16.8 shows some of the types of ashlar masonry.
Figure 16.8 Types of ashlar masonry
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