The usage of stone masonry has been carried out for thousands of years and is still one of the more popular methods of construction compared to brick masonry methods. It is a craft of arranging stones in a desired pattern to erect structures that are strong and visually pleasing. Although there are numerous stone masonry processes, ashlar masonry is a widely popular choice among people, as it blends both beauty and durability. Here we take a look at what ashlar masonry is and everything you need to know about it.
What is Ashlar Masonry?
Ashlar masonry is a kind of stone masonry that uses finely dressed stones that have uniform shape, size, and texture and are bound together using cement or lime mortar. The Ashlar blocks are usually cuboid in shape and laid in horizontal courses. The gaps between the stones are very thin and have a uniform thickness, making them hard and strong, leading to their use in a wide range of construction processes.
Types of Ashlar Masonry
Ashlar masonry is classified into six types based on the arrangement pattern and layering of stones.
Ashlar Rough Tooled Masonry
In Ashlar rough tooled masonry, the beds and sides are finely dressed using a chisel. The exposed face is dressed using a rough tool, resulting in a rough exposed finish in the masonry. Although the exposed face is rugged, the face angle should not vary more than 3 mm in any direction. This type of masonry is also called bastard masonry.
Ashlar Fine Tooled Masonry
It is the finest ashlar stone masonry, where the beds, joints, and faces of the stones are chisel-dressed to remove undulations and obtain perfect horizontal and vertical joints. The joint gaps in this masonry should not be more than 10 mm and the courses are less than 15 cm thick. These stones are laid in a horizontal course, such that stone breath should not be less than the height.
Ashlar Facing
This type of masonry work uses stones that are rough-tooled and chamfered to give a more rough look to the structure. These stones are rectangular and have straight side faces and beds, with joint thickness less than 10 mm.
Coursed Ashlar Masonry
This type of masonry lies between regular ashlar masonry and rubble masonry, where stones are hammer-dressed. Stones of the same height are laid in horizontal courses. The stones do not have a uniform shape, yet they are laid to cover the lower layer.
Chamfered Ashlar Masonry
It is a special type of ashlar masonry, where the exposed face of the stones is chamfered at an angle of 45 degrees at a depth of 25 mm. It creates a long deep line between the neighboring stones.
Random Ashlar Masonry
This type of ashlar masonry doesn’t follow any specific rule for the arrangement of stones. The stones are arranged in a random order and the vertical joints need not be stacked over the other stones.
Application of Ashlar Masonry
- These masonry works are used to build facades (exterior walls) due to their attractive looks.
- As the ashlar masonry has good interlocking, strength, and stability, it can be used for the construction of retaining walls.
- Decorative structures such as arches, columns, domes, and lintels can be built.
- Historical buildings such as forts, monuments, palaces, temples, and other religious buildings are built, as they possess highly durable properties.
- They can be used for building foundations, walls, pillars, pavements, and railroads.
- These masonry works can be used for building pathways, steps, and boundary walls.
Properties of Ashlar Masonry
Cutting & shaping
Ashlar masonry is finely cut and shaped to obtain uniform dimensions and sharp finishes to fit together with other stones and look more aesthetically pleasing.
Courses
The stones are arranged in such a way that the height of the stones should not be greater than the breadth. The stones of similar heights are arranged in horizontal courses, to obtain a symmetrical and more enhanced overall look.
Joints
Cement or lime mortar is used to bind the stones together in ashlar masonry. The mortar joints are thin and even, to give the structure a uniform look. It also provides good strength and stability for the structure.
Dressing
Ashlar masonry stones have dressed sides, beds, and faces having a smooth texture. The dressings are made using a chisel or hammer to give the stone an appealing polished look. The dressing of stone faces could vary based on the structural and aesthetic requirements.
Versatility
These masonry constructions are applicable for both load-bearing and non-load bearing walls. They are commonly used for exterior walls, pillars, and decorative walls. Their versatile properties make them suitable for numerous construction projects.
Advantages and Disadvantages of Ashlar Masonry
Advantages
- They are resistant to all types of exterior weather conditions including rain, snow, and drought.
- They have high durability and can sustain for a long period.
- This masonry construction is used for historical buildings that require a lengthy lifespan.
- They can be used for both load-bearing and non-load-bearing structures.
- The sophisticated and elegant looks make the structure stand out from other neighbouring buildings.
- As the joints are kept tight, they can withstand any type of water and moisture-related damage.
- They require low maintenance, which could save a lot of time and money.
Disadvantages
- Requires skilled labour for dressing and installing.
- Expensive masonry construction compared to other types.
- Finding high-quality stones can be challenging.
- The stones are huge and are difficult to transport and handle.
Construction Process of Ashlar Masonry
Selection of stone
The stones used for ashlar masonry are carefully selected from the quarry. They should be hard, sound, sturdy, and durable. They should not have any cracks, cavities, holes, or patches. The selected stone should be workable (liftable by hand) and its length should not exceed three times the height and the length should not be more than 3/4th of the thickness of the wall. The ideal size of the stone should be within 15 cm thick and 30 cm high.
Dressing
The stones are cut and chiselled to bring them to the desired shape and size to give a smooth texture. The stones should be made suitable for laying near the other stones in the horizontal course, with straight edges not exceeding 6 mm.
Laying of Ashlar Masonry
The mortar of appropriate consistency is prepared and poured on the surface. The stones are wetted and placed on the beds in the horizontal direction and positioned using wooden mallets. A plumb bob and string are used to check whether the stones are laid in the right direction. The stones are laid on a uniform level close to other stones, leaving minimal gaps between them.
Bonding
The bonding of the stones runs through the thickness of the wall and should not exceed 60 cm. The mortar binding between the stones should be 60 cm thick and must have uniform layering. The length of each bond stone should not be less than 2/3rd of the thickness of the wall.
Joints
The joints between two stones should not be more than 6 mm thick and the face joints should be of uniform depth of 20 mm.
Curing
The completed structure should be kept wet for a minimum of seven days and should not be exposed to heavy rains or extreme moisture conditions to avoid the washing away of mortar.
Differences Between Ashlar Masonry & Rubble Masonry
| Ashlar Masonry | Rubble Masonry |
| The stones are carefully cut and dressed to form a uniform shape and size. | The stones are irregularly shaped and are roughly dressed. |
| The stones are arranged properly with minimum joints within the course. | The stones are generally randomly laid and the gaps are filled with mortar. |
| They have uniform and polished looks, making structures more aesthetically pleasing. | They are built with irregularly placed stones and mortar joints, making them look more rough and rustic. |
| They are used in the construction of both load-bearing and non-load-bearing designing structures. | They are less formal and are generally used in non load-bearing walls. |
Conclusion
The use of stone masonry has been increasing due to its numerous advantages in the construction field. Although there are numerous types of stone masonry, Ashlar masonry has been the popular choice for more modernised construction. They are more aesthetically pleasing and can last longer, making it ideal for all types of construction.