Crawl Spaces and Moisture Intrusion

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Moisture Intrusion through Foundations

Atlanta Mold LLC News and Information

Exterior rain water runoff against a foundation is the primary cause of moisture in crawl spaces and basements. This is true whether a concrete block or poured concrete foundation.

The problem arises when runoff from rain is allowed to saturate the ground next to a foundation. This is usually caused by ground settling over time. When foundations are constructed, loose fill dirt is placed next to the foundation excavation. Because it is loose, mechanically compacting it is the standard of practice. However the soil will eventually shrink lowering the finish grade. Home gutters and rain water runoff then has easy access to the foundation.

The solution is to make sure all  rain runoff is directed away from the home. This can be done by extending the downspouts from the gutters and adding soil next to the house to raise the final grade.

Examples of moisture intrusion
Foundation MoistureFoundation Moisture

Moisture in block foundation behind finish wall

Results in wetting the finish wall surface

A common finding when foundation is below exterior grade

Note the white efflorescence

Moisture intrusion into an unconditioned living space results in elevated relative humidity.

Sustained humidity above 70% creates an environment for mold to germinate

Movement of moisture

Rain water run-off actively penetrating block foundation wall.

Exterior landscape grade must allow rain water

run-off to flow away from foundation - Always

Exterior landscaping must slope 1/2 inch per foot away from foundation

Moisture penetration

Crawl Space Block Foundation

Moisture through foundation allows mold growth

Damage occurs to foundation and support structures

Gross Water Penetration

Serious foundation water intrusion

Rain water run-off from exterior penetrates the foundation - Destructive

Water movement through foundation

Entire foundation displays efflorescence and moisture penetration

A close look at floor joists shows extensive mold amplification

Self Help Recommendations

To identify possible moisture intrusion around your home, carefully inspect the perimeter of your foundation. Look for areas where the earth ground looks to have settled next to the foundation. Landscaping by planting trees and bushes next to the house usually results in a loose and permeable soil.  Overtime this loose soil will settle resulting a downward slope towards the house.This allows rain water runoff to saturate the soil hence the foundation.

For detailed consultation on your particular moisture intrusion challenges, please call Dr. Kraemer at 770.321.6653
By |2017-04-03T23:01:27+00:00April 2nd, 2017|Building Defects, Investigation, Mold|