Moisture, in all its physical forms, is commonly regarded as the single greatest threat to the durability and long-term performance of residential homes. Over time, excessive exposure to moisture can cause significant damage to many types of building components and materials, namely corrosion, insect habitation, and wood rot. By controlling exposure to moisture, many other durability problems such as mold and indoor air quality, which can lead to unhealthy indoor living environments, can also be solved. There is wide agreement that successful management of moisture in its various forms is essential for houses to be safe, durable, and energy efficient.

Foundation drainage is an important determinant of overall exposure to moisture. It is essential that rainwater and roof drainage be diverted away from the building perimeter to prevent leaks into basements or crawl spaces, or saturation of the ground around slab-on-grade construction.

Working gutters and downspouts are a critical line of defense against foundation moisture problems in a large part of the country. Lack of gutters causes problems ranging from wet basements or foundation wall failure to cracked foundations and wall joints. Clogged downspouts or gutters, due to lack of maintenance, result in overflows with similar consequences.

We are working to identify criteria for determining when gutters should be installed, proper attachment of gutters, and most effective method for placing and sizing downspouts. We have also identified the most critical element of gutter performance, eliminating gutter debris, and we are developing products and methods that will provide solutions for long-term roof drainage and collection needs.

Common Durability Issues

Factors Influencing Durability
Frequent Durability Problems
Moisture Improper Surface Grading/Drainage
Sunlight (UV Radiation) Improper Electrical Wiring
Temperature Roof Damage
Chemicals Heating System
Insects Poor Overall Maintenance
Fungi Structural Related Problems
Natural Hazards Plumbing
Wear and Tear  

Durability By Design - A Guide for Residential Builders and Designers
U.S. Department of Housing and Urban Development.
This guide was written by the NAHB Research Center, Inc. with support from U.S. Housing and Urban Development. It is intended to raise awareness and understanding of building durability as a design consideration in housing. The guide covers basic concepts of durability and presents recommended practices for matters of moisture management, UV protection, Insects, decay, corrosion, and natural hazards.

Building Moisture and Durability
U.S. Department of Housing and Urban Development.
This project set out to develop a set of recommendation for future research on moisture problems in housing. The research recommendations were developed following a review and analysis of the extensive technical literature concerning the problems created by bulk water and excessive water vapor in houses, and the solutions to those problems.

"Working gutters and downspouts are a critical line of defense against foundation moisture problems in large parts of the country. Lack of gutters causes problems ranging from wet basements to foundation wall failure. Clogged downspouts or clogged gutters due to lack of maintenance result in overflows with similar consequences. Yet the International Residential Code has no requirements for installing gutters on pitched roofs, and no placement or sizing requirements for downspouts."

Building America Best Practices Series
U.S. Department of Energy
This Building America Best Practices guide book is a resource to help builders large and small build high-quality, energy-efficient homes that achieve 30% energy savings in space conditioning and water heating in the hot and humid climate. The savings are in comparison with the 1993 Model Energy Code. The guide contains chapters for every member of the builder's team. There is also a chapter for homeowners on how to use the book to provide help in selecting a new home or builder.

Healthy and Affordable Housing:
Building Sciences Corporation
The fundamental principles of groundwater control are to keep rainwater away from the foundation wall perimeter and to drain groundwater with sub-grade perimeter drains before it gets to the foundation wall. This applies to slabs, crawlspaces and basements (see Figures 8a, 8b and 8c) regardless of whether they are newly constructed or undergoing rehabilitation.

Preventing Moisture in Below Grade Walls
Moisture Control in Buildings
Shelter Ecology, Inc. & Environmental Building News
This article examines the physics of moisture in buildings and addresses design and construction strategies for keeping a buildings dry and allowing these buildings to dry out if they do get wet.

ASTM Manual 18, Moisture Control In Buildings, MNL 18, 1994 - Click Here
ASTM International
Brings together in one volume important data and applicable state-of-the-art relating to moisture problems in buildings: their diagnosis, prevention, and rehabilitation. This desk-top reference gives the reader information on how to design and maintain moisture-resistant buildings and how to investigate and correct moisture problems in existing buildings.It addresses residential, commercial, and institutional buildings in all North American climatic zones.

ASHRAE Handbook 2001 Fundamentals
American Society of Heating, Refrigeration, and Air Conditioning Engineers
The ASHRAE 2001 Handbook of Fundamentals is a well-established, widely known standard reference for the design of indoor environments...Causes of water entry mentioned include foundation or roof leaks, wind-driven rain, and splashing rain. Poor flashing is also mentioned as often being a major cause. Only one solution for the foundation and above-grade walls is briefly described: (1) remove rain water from the foundation with gutters, downspouts, and positive grading and (2) use rain-screen wall systems to minimize water penetration due to raindrop momentum, capillarity, gravity, and air pressure difference.

Mold In Residential Buildings
Toolbase Services
Provide drainage for roof rainwater and maintain the ground with a slope that drains water away from the foundation.

The Billion Dollar Thief: Moisture
Clemson University Housing Institute
Builder Technology Program
U.S. Department of Energy
Moisture, Building Enclosures, and Mold by Joseph Lstiburek, PhD, P.Eng.
Building Sciences Corporation
Controlling and Preventing Household Mold and Moisture Problems: A Report to Congress: U.S. Dept. of Housing and Urban Development