Waterproofing:a guide on moisture diagnosis(1st part)

WATERPROOFING GUIDE: MOISTURE DIAGNOSIS GUIDE (1st part)

 To make a successful diagnosis on waterproofing problems is quite a daunting task.

You need to have a very strong theoretical and technical background.

In the forthcoming entries we will try to simplify the theoretical part of the equation.

A right diagnosis on waterproofing demands deep knowledge of 4 different aspects:

 1. General parameters “touching” waterproofing issues.

Such parameters could – among else – be:

1.1 Surface water management

1.2 Subsurface water management

1.3 Soil types

1.4 Building materials types

1.5 Building orientation

1.6 Hydrogeologic profile of adjacent ground space

1.7 Use of building

1.8 Climatological considerations

1.9 Differences in internal and external temperatures and relative humidities.

1.10 Size, type and proximity of existing flora etc.

2. Moisture sources

Moisture sources could among else be:

2.1 Precipitation sources

2.2 New buildings moisture

2.3 Pipe leaks

2.4 Internal (lifestyle) humidity

2.5 Water vapor transported through diffusion, wind or stack effect, above or below ground.

2.6 Water used for cleaning reasons

2.7 Ground water seeping inside through envelope discontinuities or via capillary absorption.

3. Moisture transport mechanisms

Under this tag we can find:

- Massive leaks through discontinuities

- Vapor diffusion

- Wind effect

- Stack effect

- Capillary suction or absorption.

 4. Symptoms of moisture

Examples:

4.1 Salts leaching: efflorescence or cryptoflorescence

4.2 Spalling

4.3 Chemical decomposition

4.4 Physical deconstruction

4.5 Deformations

4.6 Mold growth

4.7 Metal corrosion

4.8 Wood rot

4.9 Peeling of paints, discoloration etc.

 GENERAL PARAMETERS AFFECTING DIAGNOSIS OF WATERPROOFING PROBLEMS

 A) Surface water management

Inefficient surface water management is a typical cause for many waterproofing problems in the whole building envelope and mainly in the basements.

Conversely, very often we can solve common waterproofing problem by just addressing drainage issues.

 Always check:

- If the neighboring ground slopes away from the foundation. A downward gradient of at least 5% is recommended.

- If the backfill is well compacted.

- If there is any gap between the ground and the building envelope.

- If there are any missing, defective of clogged eavestroughs or downspouts.

- If downspouts have extenders or splash pads.

Lack of a downspout is preferable than one that discharges vast amount of rainwater runoff next to the basement walls.

- If french drains function properly or are out of order.

 B) Subsurface water management

When surface water despite our best efforts percolates through the ground, it becomes subsurface water and also needs our attention.

To effectively drain subsurface water away from the building, we have two options:

 - either create an exterior perimeter drainage system

- or create an interior perimeter drainage system.

 In Greece e.g. we use only exterior drainage systems.

 The heart of the system is the perforated pipe or drain tile or weeping tile. If the heart arteries clog, the body is dead.

It’s completely the same thing with perimeter drainage.

If the perforated pipe clogs – and it happens more often than you can think – the perimeter drainage system fails.

 Chris Strogilis

Civ. Eng. – MBA – DipM

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