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Positive and negative side water proofing

Short answer

Positive-side waterproofing applies the membrane on the external face against the soil, keeping the structure dry and is preferred for new work. Negative-side waterproofing applies the membrane on the internal face, allowing the wall to remain wet and is used for repairs or inaccessible exteriors.

Describe positive and negative side water proofing system with figure.

Basement and below-ground waterproofing is classified by the side of the structure on which the membrane is applied.

Positive side waterproofing

The waterproofing is applied on the side from which the water comes, which is the outer (earth) face of the wall and under the raft. The water is stopped before it reaches the structure, so the wall itself stays dry and is protected from damage by the water. It is the preferred and more reliable system, but it needs excavation space and must be done during construction. Materials: bituminous membrane, APP/SBS sheet, bentonite, liquid-applied membrane, covered with a protection board or a brick wall.

Negative side waterproofing

The waterproofing is applied on the inner face of the wall, away from the water. The structure itself is wet and under water pressure, but water is stopped from entering the room. It is used for existing buildings or where the outside cannot be reached. Materials: crystalline coating, cementitious slurry, epoxy, waterproof plaster. The coating may peel off under water pressure, and because the wall itself stays damp, its reinforcement can corrode.

 Positive:                   Negative:
 soil|memb|wall|room         soil|wall|memb|room
 water stopped outside       water stopped inside

✓ Answer checked by Claude Opus 5.5 (high effort)

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