---
title: "Positive and negative side water proofing"
subject: "Building Technology"
chapter: 1
key: "semester_6/building_technology:waterproof-positive-negative"
source: https://www.bctengineer.com/q/semester_6/building_technology/waterproof-positive-negative
site: BCT Engineering
---

# Positive and negative side water proofing

Building Technology · Chapter 1: Functional Requirements of Buildings

- Asked in: 2076 Bhadra, 3 marks
- Video: [POSITIVE SIDE vs. NEGATIVE SIDE for Below-Ground Basement Wall Waterproofing](https://www.youtube.com/watch?v=kVK6zJJEmnw) — BUILDRITE CONSTRUCTION CHEMICALS
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/building_technology/waterproof-positive-negative
- Whole chapter: https://www.bctengineer.com/md/semester_6/building_technology/chapter-1

## Question

Describe positive and negative side water proofing system with figure.

## 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.

## Answer

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.

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

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Where is positive side waterproofing applied?
   A. On the inner face of the wall
   B. On the ceiling only
   C. On the outer face from which water comes
   D. Inside the room
   Answer: C. It is applied on the water side, the outer earth face and under the raft. (Key point: Positive side location)

2. What is true of negative side waterproofing?
   A. The wall stays dry and unstressed
   B. It is placed before excavation backfill
   C. It is always preferred in new work
   D. The structure itself stays wet and under water pressure
   Answer: D. Water reaches the wall, but is stopped from entering the room. (Key point: Negative side)

3. When is negative side waterproofing used?
   A. Existing buildings or when the outside is unreachable
   B. Only in new construction with space
   C. Only for roofs
   D. Never
   Answer: A. It is used for repairs when the outer face cannot be reached. (Key point: Use)

## Related in Building Technology

- [Positive/negative waterproofing, DPC in basement](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Awaterproof-positive-negative-dpc) — Building Technology, chapter 1
- [Below and above grade water proofing](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Awaterproof-below-above-grade) — Building Technology, chapter 1
- [Damp-proofing versus water-proofing](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Adamp-vs-waterproofing) — Building Technology, chapter 1
- [Short note: Water supply and distribution system](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Awater-distribution-short) — Building Technology, chapter 12, asked 2×
- [Principles of laying out water supply system](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Awater-supply-principles) — Building Technology, chapter 12

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