How to Construct Ashlar Masonry? [PDF]

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Ashlar masonry is a type of stone masonry that is formed using finely dressed stones of the same size, shape, and texture laid together in cement or lime mortar of equal size joints at right angles to each other.

The masonry built using ashlar stones is rectangular, where cuboid blocks are laid in horizontal courses or layers. The joints between the stones are very thin, regular, and of uniform thickness, which makes the ashlar masonry very strong and sturdy.

Specification of Stone used for Ashlar Masonry

The stone used for the construction of ashlar masonry shall be hard, sound, durable, and sturdy, free from cracks, decay and weathering, and defects like cavities, cracks, flaws, sand holes, veins, patches of soft or loose materials, etc.

The stones used should be small enough to be lifted and placed by hand. The length of the stone shall not exceed three times the height, and the breadth on base shall not be greater than three – fourth of the thickness of the wall not less than 15 cm. The height of the stones may be up to 30 cm.

Dressing of Stone for Ashlar Masonry

1. Each stone shall be cut to the required size and shape, to be free from waviness and to have truly horizontal and vertical joints.
2. The faces that remain visible in the final position shall be fine chisel-dressed.
3. The top and bottom faces that form the bed joints shall be chisel-dressed, so that variation from 60 cm straight edge does not exceed 3 mm. 
4. The vertical joints forming faces should be chisel-dressed, so that variation with 60 cm straight edge shall not exceed 6 mm.
5. Any vertical face to come against the backing of masonry shall be dressed such that variation from the straight edge must not exceed 10 mm.
6. All angles and edges that remain exposed in the final position of the ashlar masonry shall be accurate, square, and free from chipping.

Laying of Ashlar Masonry

1. All the stones shall be wetted before placing them in position. 
2. The stones shall be floated on mortar and bedded properly in position with wooden mallets without the use of chips or underpinning.
3. The walls and pillars constructed with ashlar masonry shall be carried up truly plumb or battered.
4. All vertical joints shall be truly vertical, and stone courses shall be laid truly horizontal.
5. In the case of ashlar work without backing of brickwork or coursed rubble masonry, face stone shall be laid headers and stretchers alternatively.
6. The headers shall be arranged as closely as possible in the middle of stretchers above and below. 
7. The stones in the ashlar masonry shall be laid in regular courses of not less than 15 cm in height, and all the courses shall be of the same height.
8. For ashlar facing with the backing of brickwork or coursed rubble masonry(figure 1), face stone shall be laid in alternate courses of headers and stretches unless otherwise directed. 
9. All connected masonry in a structure shall be carried up nearly at one uniform level throughout, but where breaks are avoidable, the joint shall be made in good long steps so as to prevent cracks developing between new and old work.

Bond Stones in Ashlar Masonry

1. The bond or through stones running right through the thickness of walls shall be provided in walls up to 60 cm thick.
2. For all thicknesses of such walls, a set of two or more bond stones shall be overlapped each other by at least 15 cm.
3. The length of each such bond stone shall not be less than two-thirds of the thickness of the wall.
4. At least one bond stone or a set of bond stones shall be provided for every 0.5 sq m of the area of the wall surface.

Joints in Ashlar Masonry

1. All joints shall be full of mortar, which shall be not more than 6 mm thick.
2. The face joints shall be uniform throughout, and a uniform recess of 20 mm depth from face shall be left with the help of the steel plate during the progress of work.
3. All the joints shall be finished with pointing sunk from the stone face by 5 mm, and the depth of mortar in pointing work shall not be less than 15 mm.

Curing of Ashlar Masonry

1. The masonry work in cement or composite mortar shall constantly be kept moist for a minimum period of seven days.
2. In the case of masonry with fat lime mortar, the curing process shall start two days after laying of masonry and shall continue for at least seven days thereafter.

FAQs on Construction of Ashlar Masonry

Read More:
1. Ashlar Masonry and its Types
2. How to Dress Natural Building Stones? [PDF]