Plastering and Pointing

Definition

Plastering is the process of applying a thin layer of mortar to the internal or external surfaces of walls and ceilings to provide a smooth, durable, and aesthetic finish. Pointing is the specialized process of finishing or repairing the mortar joints between bricks or stones in a masonry structure to improve weather resistance and appearance.

Main Content

1. Types of Plastering

Internal Plastering: Uses lime or gypsum-based mortars to provide a smooth surface for painting or wallpapering inside buildings.
External Plastering (Rendering): Uses cement-based mortars to protect exterior walls from harsh weather conditions like rain and wind.

2. Types of Pointing

Flush Pointing: The mortar is pressed into the joints and finished flush with the face of the brickwork, providing a simple, clean look.
Recessed Pointing: The mortar is pushed back into the joint, creating a shadow effect that highlights the texture of the individual bricks.

3. Purpose of Mortar Joints

Structural Integrity: Mortar bonds individual masonry units together, distributing loads evenly across the structure.
Weatherproofing: Properly filled joints prevent moisture, pests, and air from entering the building envelope, preventing decay.

Working / Process

1. Surface Preparation

The surface must be cleaned of loose dust, dirt, or oil; for old brickwork, this involves raking out old mortar to a depth of 10–20mm.
The area must be thoroughly dampened with water (curing) so that the dry masonry does not absorb water directly from the fresh mortar.

2. Application of Mortar

For plastering, the mortar is applied using a trowel and leveled with a wooden float or screed.
For pointing, mortar is pushed into the joints using a small pointing trowel, ensuring no air gaps remain behind the material.

3. Finishing and Curing

The surface is smoothed or textured using a sponge or float to achieve the desired finish.
Curing involves keeping the surface moist for several days to ensure the mortar sets slowly, which prevents cracking and increases structural strength.

Cross-section view of a brick wall joint:

      |      |
      |Mortar|  <-- Joint filled with fresh mortar
      |      |
    --+------+--
    | Brick  |
    +--------+

Advantages / Applications

Durability: Both processes protect the core material (bricks or concrete) from moisture, significantly extending the lifespan of the structure.
Aesthetic Appeal: Plastering creates a clean, uniform wall surface, while pointing defines the pattern and color of the masonry work.
Thermal Efficiency: Sealed joints and plastered walls reduce air leakage, helping to maintain a consistent internal temperature within the building.

Summary

Plastering and pointing are essential finishing techniques in construction that enhance both the structural integrity and aesthetic value of a building. Plastering involves covering large surfaces for protection and smoothness, while pointing focuses on the joints between masonry units to ensure water resistance. Together, these processes prevent decay and create a durable, weather-tight shell.

Important terms to remember: - Mortar: A mixture of binding material (cement/lime) and sand. - Curing: The process of keeping mortar moist to gain strength. - Raking: The removal of old, loose mortar from joints before pointing.