ADVICE

Reader's question:

"For the external surfaces of the building, which is the best admixture for the final layer of the plaster? Marble dust or sand?"

Our answer:

Plastering, usually takes places in three layers. The mixture of the final layer contains either:

- sand and gray cement or

- marble dust and white cement. 

The advantage of the marble dust is that the final surface becomes smooth, white and ready to be painted. However, they might appear on the surface several "damages" due to either harmful addmixture in the marble dust (the dust was not clear) or due to the grain size of the marble dust. The grains must be neither too large nor too small. 

On the other hand, the sand should come, if possible, from rivers. In case that comes form the sea, then it should be meticulously cleaned from salt and other admixtures. If it is not cleaned, then several damages, cracks, stains should be expected to appear on the surface. 

Finally, the cost should be considered. In some areas, marble dust plus white cement are an explensive solution. In other areas, the cost of tranfering the sand is higher and thus it is preferable to use marble dust. 

  wall finishing, ceiling finishing