Which of the following waterproofing methods is often used for external surfaces of concrete structures? 

Explanation:

Membrane waterproofing

• Involves applying a waterproof material (e.g., bitumen, PVC, EPDM) to external concrete surfaces.

• Creates a barrier to prevent water infiltration.

• Commonly used for roofs, basements, and foundations of concrete structures.

Additional Information Root barriers

• Used to prevent plant roots from penetrating concrete structures.

• Commonly used in landscaping, especially for green roofs.

• Not a waterproofing method but can protect concrete from root damage.

​Cavity wall construction

• Involves creating a gap (cavity) between two walls for insulation and moisture control.

• Helps reduce dampness but not a direct waterproofing solution.

• Primarily used in wall construction, not specifically for external surfaces of concrete structures.

Integral waterproofing

• Involves adding waterproofing chemicals to the concrete mix itself.

• Reduces water permeability within the concrete.

• Suitable for internal use, not specifically for external surfaces of concrete structures.