Pointing is the art of finishing the mortar joints of the walls or similar structures with either cement mortar or lime mortar in order to protect the joints from atmospheric agencies and also to improve the appearance of the structure.
Pointing is often done in an entire wall or whole structure because it is difficult to detect defective points, and adjacent joints may also be in need of repair. It is done up to the depth of 10 mm to 20 mm.
1.1. When Pointing is Done?
Pointing is restored to:
a. Where a uniform and smooth surface is not required.
b. Where the exhibition of the natural beauty of the materials such as stone blocks, bricks, etc. used in construction is to be made.
c. Where the materials used in construction can withstand the effects of weather.
d. Where the workmanship is quite good.
1.2. Importance of Pointing
Some importance of pointing work are:
a. It helps to seal the voids or spaces which may carry water and causing decaying of joints mortar.
b. Regular maintenance is reduced if pointing work is done properly and aesthetically.
c. It gives strong and reliable bond finishing at joints of bricks /stone masonry.
d. It also has scope in various places even in low precipitating areas.
1.3. Uses of Pointing
Some uses of Pointing are:
a. It can be used to fill the gaps at joints of brickwork walls using cement mortar.
b. Repointing can be done to maintain and repair the cracks on the structures.
c. Stones can be used for pointing in the stone masonry to make the structure strong and stable.
d. Sometimes, people also do pointing to give an aesthetics look to their building.
1.4. Mortars Used in Pointing
a. Lime Mortar
Lime mortar is prepared by mixing a suitable proportion of fat lime, fine sand and water. Generally, lime mortar of ratio 1:2 or 1:3 ratio is used for pointing work.
It is used in the pointing of:
i. New buildings and structures with traditional methods
ii. Old buildings
b. Cement Mortar
Cement mortar is prepared by mixing a suitable proportion of cement, sand, and water. Generally, cement mortar of ratio 1:3 is used in pointing work. The prepared mortar should be used within 30 minutes to avoid the early setting of the mortar.
It is used in the pointing of new buildings as well as old buildings.
c. Surkhi Mortar
Surkhi mortar is the mixture of lime, surkhi, and water in a suitable proportion. Generally, surkhi mortar of ratio 1:2 is used in pointing work.
It is mostly used in the pointing of old buildings and structures.
1.5. Types of Pointing
a. Struck Joint Pointing
The upper portion is inside the face of masonry by 12 mm while the bottom portion of the pointing is flush with masonry.
b. Tuck Pointing
~ The joint, after having been raked, is filled with cement mortar.
~ A groove 6 mm wide and 3 mm deep is formed along the center of the joint while the previously applied cement mortar is soft.
~ The groove is filled with lime putty which projects by 3 mm. Lime putty is sometimes replaced by cement.
~ This pointing gives a pleasing appearance.
c. Recessed Joint Pointing
~ Mortar is pressed behind the walls.
~ It is used for high-class masonry work.
d. Flush Pointing
~ It is suitable for brick as well as stone masonry.
~ The raked portion of the joint is filled with mortar and surface made flush to the masonry for trowelling.
e. V-groove Jointing
~ It derives its name for its shape.
~ It is suitable for rubble and ashlar masonry work.
f. Keyed Joint Pointing
~ After filling the joints with mortar a semi-circle is formed inside the pointing by some tool.
~ The pointing gives an elegant appearance.
g. Weathered Joint Pointing
~ As the name suggests, this type of joint gives adequate protection against weathering. However, it requires a comparatively large quantity of water.
h. Beaded Pointing
~ Although it gives a good appearance, it is unstable and easily gets damaged in comparison to other types.
1.6. Procedure for Pointing
~ Prior to pointing, all the mortar joints on the face are raked out by a special pointing tool to a depth of about 7/4 cm to provide an adequate key for the fresh mortar used for pointing.
~ All the loose mortar and dust are then brushed out of joints and the wall surface is well washed, wetted with clean water, and kept wet for a few hours.
~ The joints after being prepared, are filled with lime or cement mortar with a small trowel.
~ The mortar is well pressed into the joints to ensure solid contact with the internal old mortar joints. Excess mortar sticking the sides is scraped away carefully.
~ The finished pointing is kept wet for about 4 days for lime pointing and 10 days for cement pointing.
1.7. Precautions for Pointing
a. Mortar used should be fresh.
b. In old structures or buildings; the joints should be wetted properly before starting pointing work as mortar may not stick on a dry surface.
c. Type of mortar and pointing should be chosen as per the requirement of the job/work.
d. Pointing work should not be carried out during the frost weather as it may lead to the disintegration of joints due to the action of freezing.
1.8. Advantages of Pointing
a. It avoids cracking and shrinkage at joints.
b. It provides resisting property to bricks and stones masonry against weathering to some extent.
c. Stone masonry may be defective for which portland cement can be used in mortar for tuck pointing purposes to maintain and repair the damage.
d. Voids or spaces are present between brick/stone masonry which can be fixed by pointing work to reduce the entrance of water through it.
e. Thermal property of wall can be maintained by insulating the cavities with repointing work.
f. Repointing integrates the structural parts with brickwork giving enhanced finishing.
g. It reduces the further damage of the brick wall.
h. It requires less amount of cement mortar.
1.9. Disadvantages of Pointing
a. It is reliable only for joint fillings.
b. It cannot be done for the interior part of the walls.
c. It doesn’t give smooth and plain aesthetics appearance if it is not done properly.
d. Brick/stone masonry may have defects even after pointing.
e. This can’t be done in heavy rainfall areas.
f. Inadequate sitting of pointing may results in spider web effect on stonework with cracks.
h. Bricks/stone masonry pointing can be difficult to paint.
|Read Also: Hempcrete|