Detailed Guide to Plastering, Tile and Coating Area Calculation Rules
Created on 07.21
In construction cost estimation and project management, accurate calculation of plastering, tile, and coating quantities is essential.
Although these finishing systems are all measured by area, their calculation methods are different due to their construction processes and application characteristics.
Based on GB/T 50854-2024 Standard for Calculation of Building Construction and Decoration Engineering Quantities, understanding these differences helps contractors, engineers, and material suppliers improve quantity estimation accuracy and project cost control.
1. Plastering Area Calculation Rules
Plastering quantities are mainly calculated based on the vertical projection area of the structural surface.
For interior wall plastering:
- Without dado: calculated from finished floor level to ceiling bottom;
- With dado: calculated from the top of dado to ceiling bottom;
- With suspended ceiling: usually calculated to the ceiling bottom plus 100mm.
Exterior wall plastering is calculated according to the vertical projection area of the external wall.
For deduction rules, wall dado, door and window openings, and openings larger than 0.3㎡ should generally be deducted. Skirting lines, picture rails, connection areas, and openings smaller than or equal to 0.3㎡ are usually not deducted.
Door and window sidewalls are generally not added separately for plastering, while attached columns, beams, piers, and chimney sides should be included.
2. Tile and Stone Area Calculation Rules
Tile and stone quantities are calculated based on the actual installed surface area.
This applies to:
- Wall tiles
- Floor tiles
- Stone finishes
- Decorative panels
The biggest difference from plastering is:
Door and window sidewall areas must be included.
If tiles are installed inside window reveals or door openings, these areas are considered actual installation surfaces and should be included in quantity calculation.
For floor tiles, areas occupied by structures, equipment foundations, pipes, and trenches should be deducted. Partition walls and small areas below 0.3㎡ are generally not deducted.
3. Coating Area Calculation Rules
Coating quantities are generally calculated according to the designed surface area.
This applies to:
- Exterior wall coatings
- Latex paint
- Stone-like coatings
- Sand-textured coatings
However, coating calculation methods may vary depending on regional standards.
Two common approaches are used:
1.Calculation based on plastering area
2.Calculation based on actual painted area
Therefore, coating quantities should always follow the latest local standards and project requirements.
4. Key Differences Between Plastering, Tile and Coating Calculation
Item | Calculation Basis | Door/Window Sidewalls |
Plastering | Vertical projection area | Usually excluded |
Tiles | Actual installed area | Included |
Coatings | Depends on local standards | May vary |
5. Important Considerations for Quantity Calculation
To ensure accurate calculation:
- Confirm the applicable local standards;
- Understand opening and special area calculation methods;
- Distinguish projection area from actual installation area;
- Estimate material quantities according to project requirements.
Accurate quantity calculation helps control project costs, optimize material planning, and improve construction efficiency.
For construction companies and building material suppliers, understanding these rules helps achieve better project management and more accurate product selection.
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