Basements, Crawlspaces & Foundation walls

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Basements, Crawlspaces & Foundation walls

Basement Maintenance:

Basement Walls:

Basement walls are constructed out of several materials such as poured concrete, cinder block, stone, and occasionally wood. One common problem associated with basement walls is moisture penetration.

Water Penetration:

	Approximately 60 percent of all basements in this country suffer from some form of below ground wetness. Block foundations are especially vulnerable, with an 80 to 90 percent chance of leakage within the first 20 years”. It is estimated that 98 percent of all basements will leak at some point during their life. It is rare that water penetration will cause structural damage, but a wet basement can be a major inconvenience causing damage to interior finishes or personal items.
	Moisture problems in a home can be intermittent - leaking after every rain or, occurring only after heavy rain. Still, some homes may only leak during wind driven rains or during a spring thaw. In most cases, the damage that is caused gives no indication of frequency.
	It is estimated that 90 percent of all wet basement problems are caused by surface water (rain or snow) collecting around the building. Before investing thousands of dollars on a waterproofing system, it makes sense to get the water flowing away from the home first.

KEEP YOUR BASEMENT DRY!

Gutters and downspouts play an important role in diverting water away from the building:

	Clean the gutters and downspouts in the spring and fall (or as needed).
	Make sure that the gutters drain and are sloped towards the downspouts.
	Be sure the downspouts are extended well away from the foundation (4 to 6 feet is usually adequate).
	Improper grading around a home can be another factor in a wet basement. Re-grading the exterior landscaping to direct water away from the building rather than towards it, can be another effective solution to moisture problems. Ideally, the ground should slope down and away from the home at a rate of one inch per foot for the first six feet. A soil

Crawl Spaces:

Any area under a home with less than full headroom is called a crawl space. According to many codes, there must be at least eighteen inches of clearance between the bottom of the floor joists and the ground and twelve inches under beams.

Crawl spaces should be dry. The crawl space floor should be protected against moisture entry with a vapor barrier. Plastic sheeting, felt paper, or concrete are common materials used. Proper steps should be taken to allow ventilation within the crawl space.

Typically, one square foot of ventilation per 1500 square feet of crawl floor is adequate, provided a vapor barrier has been installed. If a vapor barrier is not present, one square foot of ventilation per 500 square feet of crawl is suggested. Good ventilation and a vapor barrier will significantly affect the moisture levels in the crawl space. It reduces the likelihood of structural damage, pest infestations, and a musty odor in your home.

Periodically inspect the crawl space for signs of moisture.

Open the crawl vents in the warmer months.

Close the crawl vents in the winter months.

Beams & Columns:

The purpose of a support beam is to carry the weight of the floor and walls horizontally to the foundation or columns. Typical materials for support beams are steel, wood, or laminated plywood. Steel beams can be much stronger than wood and are much more resistant to rot and insect and mechanical damage. Steel beams should rest on steel or masonry columns. The newer, laminated plywood beams can be stronger than the solid wood type. These beams are lighter and less expensive than steel beams. Wood beams can rest on wood columns.

The purpose of a support column is to carry the weight of a beam down to a footing. Typical materials for support columns are steel, brick, concrete block or wood. Every support column should have a concrete footing underneath that compacts well causes water to run across its surface. This is the preferred material to use.

Periodically inspect the soil around the perimeter of your home making sure that water is sloped away from the foundation.

Any abnormal slanting, sloping or leaning of your floors, walls, or ceilings should be promptly investigated.

Periodically inspect wood beams or columns for moisture damage, pest infestation or warping (especially in crawl spaces).

WALL CRACKS:

Regardless of their construction, walls crack because they are overloaded or because the structure has settled or heaved. Vertical and angled cracks are usually caused by settlement or heaving. Horizontal cracks are more likely to be load induced or caused by side pressure.

NOTE: Surface cracks that do not pierce the wall and are not accompanied by displacement are not structural in nature and should be distinguished from the cracks discussed here.

VERTICAL CRACKS:

If a wall has an upwards overload adjacent to a downwards overload, it may crack vertically so that one side rises or sinks with respect to the other. Vertical cracks are usually caused by settlement, compaction, or soil eroding under the footing. Overloading from above can occur when framing members fail forcing loads to areas that were not designed for them. Similar cracks can also be caused by overloads from below, such as frost or hydraulic expansion of the soil.

ANGLED CRACKS:

When up and down loads are applied so the forces are offset from one another, cracks are likely to occur at an angle. Cracks of this type may be found when there is a major discontinuity in the soil or if a building is built on expansive clays.

HORIZONTAL CRACKS:

When a wall is overloaded from the outside, as from frost, soil pressure, or improper backfill, it may bow inward and crack horizontally. In a block wall, the crack is usually in a mortar joint and is wider on the inner face. An additional cause of horizontal cracking may be settlement of the foundation. If a foundation is laid on top of unstable soil, the wall which lacks the proper support could drop resulting in a horizontal crack without vertical displacement of the wall surface.

Note: Surface effects such as poor grading or improperly located downspouts can increase the amount of water pushing against the basement wall.

CATASTROPHIC FAILURES:

Walls are strongest in compression. As a result, they prevent a catastrophic failure which occurs from vertical loading in the absence of a horizontal component. Failure generally occurs when a horizontal component of the load causes the center of gravity of the wall to move beyond its base. The center of gravity is the midpoint of the mass of he wall. Unless it is specifically constrained, an object will overturn if its center of gravity moves outside its base.

Signs of possible foundation failures include:

	Horizontal cracking or wall out of plumb.
	Excessive bowing inward or outward.
	Large vertical cracks (in excess of 1/4 inch).

Note: The Information contained within this website is for informational purposes only. Kevin M. Leonard & The Home Inspection Company always recommends that a qualified expert be consulted in the area of concern.

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