The primary difference between building sand and plastering sand lies in their processing and resulting purity, which affects their performance in specific applications like mortar and render.
Understanding the Key Differences
While both building sand and plastering sand are derived from natural sand deposits, they undergo different levels of processing tailored to their intended uses in construction.
Processing and Purity
The most significant distinction is how the sand is prepared:
- Plastering Sand: According to the provided reference, in order to make plastering sand, all the particles are cleaned and washed in order to take out the salt, silt and clay content. This rigorous washing process removes fine particles and impurities.
- Building Sand (or Sharp Sand): Building sand is typically less processed. It may contain higher levels of silt, clay, and organic matter. Its grain shape is often sharper and more angular compared to plastering sand.
Composition and Application Performance
The difference in processing directly impacts how the sand performs when mixed with binders like cement or lime:
- Plastering Sand: Because it is cleaned of impurities like silt and clay, plastering sand provides a cleaner aggregate for mixes used in plastering and rendering. The absence of these fine materials results in a smoother finish and, importantly, less shrinkage and cracking once it has dried, as noted in the reference. This makes it the preferred choice for applications where a smooth, crack-resistant surface is crucial, such as interior plastering or exterior rendering.
- Building Sand: Building sand is commonly used for general building applications like mixing mortar for bricklaying or blockwork. Its coarser, more angular nature provides good strength and workability for these purposes. However, the presence of silt or clay in significant amounts can weaken mortar or lead to issues like increased shrinkage or efflorescence (white powdery deposits) in finishes.
Comparison Table
| Feature | Plastering Sand | Building Sand |
|---|---|---|
| Processing | Thoroughly cleaned and washed | Less processed |
| Purity | Low salt, silt, and clay content | May contain higher levels of silt and clay |
| Particle Shape | Generally finer and rounder (though can vary) | Often coarser and more angular |
| Primary Use | Plastering, Rendering | Mortar for bricklaying, blockwork, concrete mixes |
| Performance | Less shrinkage and cracking in render/plaster | Good workability and strength for mortar |
Practical Considerations
Choosing the correct type of sand is vital for the success and longevity of construction projects. Using building sand for a finish coat of plaster or render would likely result in a rougher texture, increased risk of shrinkage cracks, and potentially efflorescence due to impurities. Conversely, while plastering sand could technically be used for mortar, its finer composition might affect the desired bond strength and workability compared to traditional building sand.
Ultimately, the processing and purity of plastering sand are specifically designed to achieve smooth, durable, and less crack-prone finishes, making it distinct from the more general-purpose building sand.
