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Moisture Control Outside the Home

Believe it or not, 90 percent of the moisture on the outside of a home can be controlled by properly installed and maintained gutters. Water allowed the collect next to a foundation can cause cracks. The water will eventually get under the foundation. This can lead to plumbing leaks within the foundation, compounding the problem. If the grading around the foundation is too high this could allow water entry into the home at the ground floor level.

Prevention 

• Install and maintain proper guttering around the home. Ensure the turn-out at the end of the down spout is long enough to adequately carry water away from the residence.
• Ensure proper clearance between the foundation grade and outside wall materials. Typically 6 to 8 inches should be maintained.
• Grading around the foundation should slope away from the home, typically at least 6 inches in 10 feet. If that cannot be achieved, a swale or french drain may be needed.
• Ensure all exterior windows and entry points into the home are properly flashed or caulked where they intersect with siding materials. Using caulk constitutes routine maintenance periodically regardless of manufacturer claims of longevity. 

Extreme case of trapped moisture and it's affects in the crawlspace of a home. Lack of ventilation is the primary cause. 

Extreme case of moisture damage and it's affects. Lower right corner shows a shorted dryer electrical outlet.

 Moisture Control On The Roof

Moisture allowed to pond or remain on roofing materials will cause them to deterioate at a much faster rate than what the manufacturer warrants.

When roofing material remains wet this can cause algi to form. When algi grows it will begin to cause the small aggregate embedded in asphalt shingles to flake off. When enough aggregate is removed from the shingle, the black asphalt is exposed which is highly susceptible to damage from UV rays.

Prevention  

• Do not allow leaves and small tree limbs to collect on the roof. These are areas where the roofing materials will not be allowed to dry completely.
• Areas of shading are particulary vulnerable to moisture and algi growth because the roofing material may not ever get a chance to thouroughly dry. Trim limbs back away from the roof line.
• Roof valleys should remain clear of leaves and debris to ensure water can flow into gutters.
• Areas where a roof intersects a wall can be vulnerable to water entry into the home, Ensure there is proper flashing and proper clearance between the wall and roofing material.
• Ensure proper flashing exists at the roof perimeter, chimney, plumbing vents, skylites.

Plumbing vent terminated in attic area introducing moisture and septic fumes into the home. 

Grading too high and lack of guttering is the result.

 Moisture Control In The Home

When moisture is not removed from the interior of a home it can lead to mold and deterioation of anything within the home. It can cause buckling floors, drywall damage, wall and roof structural deterioation.

Not long ago, home builders were not too concerned about moisture levels within a home. They built homes using "tight" construction techniques and materials such as 6 mil plastic sheathing installed on the inside of exterior walls and ceilings. This coupled with inadequate ventilation caused big headaches with home insurers. Builders have a wide range of new materials, techniques, and devices designed to prevent moisture buildup within the home. If you are planning a newly constructed home, insist on these. Some of it is called "Green Building". I just call it "Smart Building".

Techniques

• If building a pier and beam home, consider having the crawspace conditioned rather than vented. This will save money when heating and cooling the home, reduce the amount of insulation required and most important drastically reduce moisture entry into the home.
• Where exterior walls will contain siding consider a skin vent which allows the wall to vent out the roof. This allows the wall insulation to perform more adequately and will remove any moisture buildup within the walls.
• Ensure a wind and moisture barrier is used to envelope the exterior walls prior to installing the finished exterior. Tyvek is a popular choice. This allows moisture to exit the structure but does not allow it to enter. It also acts as a windbreaker for the home and prevents "windwashing". This movement of air within insulation dramatically reduces it's performance.
• Do not install a moisture barrier on the inside of exterior walls, or ceilings. If you plan on a conditioned crawlspace do not place a moisture barrier between it and the floor. Moisture must be allowed to escape the home.
• Insist on a continuous vented roof ridge installed on all peaks in the roof.

Prevention

• Any room that has a source of running water is a source for increased moisture levels within a home and should have a mechanical means to vent. Bathrooms and kitchens are sources of large amounts of moisture introduction to the home.
• Bathroom, kitchen, and any exhaust fan including the clothes dryer should vent to the outside of the house, not into the attic or under the house.
• An unconditioned crawlspace requires adequate ventilation. Vents should be installed on all sides. High moisture content under the house can damage and weaken structural members as well as provide a never ending source of moisture entry to the home.
• Check all plumbing fixture connections for leaks. Clothes washer, sinks, toilets, dishwasher, water softner, hydromassage units, ice makers, should all be checked on a periodic basis.

 Innovative Building Techniques

The conditioned crawlspace. Does not require ventilation of the exterior foundation walls. Requires insulation of interior of external foundation wall only. The ground beneath the crawlspace remains cool during summer months and warm during the heating season. Exterior of foundation wall below grade should be moisture proof to prevent seepage into the area. Interior of crawlspace could double as additional storage area. Imperative to prevent any moisture entry into the crawlspace area or it will fail. Heavy duty, high strength plastic sheathing covers the entire crawlspace area and extends up to the floor joists preventing moisture transpiration from the ground and walls. A sump pump is installed is the event that moisture does get into the area due to extreme environmental conditions.

The skin vent installation. After Tyvek or comparible material is installed on the structure, 1 X 4 lumber is attached generally on 16 inch centers on the area where siding is to be installed. The siding is then attached to the 1 X 4 material which allows for a 3/4" gap between it and the exterior wall. This allows the wall to vent into the soffit area and up the roof line and out the ridge vents, thus preventing moisture buildup. This also allows a structural solar barrier sheathing which is behind the Tyvec to function properly and allows the wall insulation to perform as it should.