Basics in Building Construction

Basics in Building Construction 4(2+2)

Lesson 09 : Stone Masonry

Precautions In The Construction Of Stone Masonry

• Stones should have homogenous structure. They should be strong, hard, tough, close grained and should be of uniform texture.
• Stones should be well watered before using in the construction so that they do not absorb moisture from the mortar instantaneously.
• Immediate withdrawal of water from the mortar affects the hardening process of mortar and renders it to be weak.
• Stones should be free from defects, flows, soft patches, cavities and cracks. They should be dressed well as per the requirement.
• Cement mortar, lime mortar, cement and lime mortar, lime surkhi mortar may be used for stone masonry construction.
• Stone masonry in foundations may be constructed with 1:3 cement sand mortar in case if the soil has sulphate content. In other cases 1:1:6 cement, lime, sand mortar can be used.
• The mortar used should have adequate workability.
• Stones should be laid on their natural bed.
• Proper bond should be maintained throughout the work.
• Continuous vertical joints should always be avoided.
• Stone masonry is least resistant to tensile stresses, hence it should be ensured that no tensile stresses are allowed to develop anywhere in the masonry.
• The face and back of the stone wall should be well bonded together by using bond stones at frequent intervals. Bond stones should be laid in staggered fashion in successive courses with a maximum internal distance of 1.50 meters. The whole masonry work should be raised uniformly so that no unequal loading occurs in foundation.
• If it becomes necessary to break the uniformity the wall should be racked back at 450 to allow proper connection between the old and the new work.
• Quoins used at corners and at door and windows should be of full height of the course.
• Length and breadth of stones used at quoins should be at least twice or 1 ½ times their depth.
• Very small size stones should not be used in the masonry.
• All the cavities in the masonry must be filled up with spalls and mortar mixture. All the exposed joints should be raked to a depth of 25mm and pointing should be done with rich cement mortar.
• The entire masonry should be cured for at least 10 days.
• The scaffolding used in stone masonry construction should be strong enough to bear the load. Double scaffolding is most suitable one since no holes need to be left in the masonry for putlogs.
• The bed joints should be uniform and should be thoroughly filled up. Stones should have level surfaces at bottom so that no hollow is left in the bed joints. Hollow addressed bed joints may lead to cracks in the stone under loaded condition.
• Hard stones without flaws should be used as bed blocks below the beams.
• Before constructing new stone masonry work over old one, the old stone masonry should be cleaned with wire brushes and watered sufficiently. Chases for dowels, clamps etc. should be made prior to starting of work. Suitable lifting devices should be used to lift large sized stones.
• The entire work should be carried out under good supervision and good workman ship.