Foundations and Yard

 

Site Safety

Periodically walk around the yard with an eye to safety. Have holes dug by dogs, which might trip someone, filled with soil. Are sidewalks and driveways free of clutter and tripping hazards, like raised edges? Are covers for water meters or lawn sprinkler control boxes properly installed? Look for low hanging branches, wires or other hazards. Corrective action now, may prevent grief later. Gather old or unused paints, insecticides, toxic cleaners and depleted household batteries for hazardous waste pickup or delivery to an approved disposal site.

 

The Soil Your Foundation Rests On

Elastic-soils, as are typically found in this region (San Antonio), exhibit a great amount of expansion and contraction with varying moisture contents. Clay soils that become too dry will shrink and will not be able to physically maintain the elevation of a structure’s foundation. Conversely, clay soils that become over-saturated can easily lose their load bearing capacity. Various factors control the moisture contents of clay soils. Probably the most significant of these is the seasonal moisture changes which occur as a result of varying weather conditions. Soil desiccation as a result of the hot, dry summer months can have a devastating effect on structural foundations in this region. High ambient temperatures, in conjunction with long periods of inadequate rainfall, can cause moisture loss in soils up to several feet below the surface.

This moisture loss is compounded when trees or bushes, which actively consume water from both the surface soils, are located in close proximity to a building’s foundation.

 

Foundation Watering: Maintaining Your Foundation

Keep an eye on the soil conditions around your house. One way to tell if the soil is too dry is to examine the “soil line” at the perimeter of the house. If the soil line (where the soil meets the concrete beam) has pulled away from the foundation more than 1/8” it is time to water. Ideally, the soil should be kept moist enough so that it is continuously snug against the concrete beam wall. NOTE: If you find that the soil has pulled away from the beam wall more than this amount, do NOT add water directly INTO the separation! If water is put directly into the soil line separation, it may settle at the bottom of the concrete beam wall and make the soil in that area TOO WET to adequately support the wall. Instead, water the area “just as a rainstorm would” with a sprinkler system or soaker hose. The separation should close by itself in a few days. Water the foundation in a uniform, systematic manner. Use of an automatic sprinkler system and/or soaker hoses (placed about 18 inches from the perimeter beam wall) are effective watering methods if used correctly and regularly. The key is to keep the soil around the perimeter of the house moist, but not muddy. As a rule, watering every day for about 20 minutes is usually sufficient. Please note, that substantially MORE watering of the foundation may be required during very hot, dry periods.

 

Trees and Shrubs

Do not plant trees and bushes next to the foundation. Trees in particular should be planted no closer to the foundation than their expected mature height (i.e. if a tree is anticipated to grow to a height of 30 feet, it should be planted at least 30 feet away from the house.) Certain fast growing bushes (e.g. red tipped photenias) should be avoided completely if possible. Keep in mind that the reason these bushes grow so fast is because they consume large amounts of water! Trees should be planted far enough away from the house that their canopy would not overhang the roof when they are fully mature. A tree’s root system mimics its canopy. Roots growing under a foundation can destabilize it in several ways for instance, by removing moisture from the soil that a foundation needs for its structural support. When trees are close to the house, their limbs should never touch the building, or serious damage can result. Be aware, too, that growing root systems can lift sidewalks, patios and driveways, causing damage and creating trip hazards.

 

Slab-on-Grade/Concrete Foundations (Most Common in San Antonio)

Foundation walls are usually made of poured concrete. Foundation walls are subject to a wide variety of stress and strain. Combined stress and temperature variations may cause cracks in the foundation walls. Walk around the house studying the edges of the foundation. Look for cracks in the edges or soil separation from the edge of the slab and unusual discoloration or water stains, mud or mounded dirt piles on the slab edge. Cracks in the foundation edge may indicate foundation movement or settling. Some cracks are not unusual and may not be structurally significant, but if in doubt, have a qualified structural engineer or other expert evaluate them. Discoloration and/or water stains can indicate a plumbing leak in the house and should be further evaluated, but if in doubt, have it evaluated by a qualified plumber. Mud or mounded dirt piles on slab edges may indicate destructive or hazardous insects invading the house. Again, call an expert or qualified pest control operator.

 

Pier and Beam (Common for Homes Built Before the 1960’s)

Foundation walls are usually made of poured concrete, masonry blocks or wood framing. Walk around the perimeter of the house looking for cracks or damage to the crawl space skirting and ventilation openings. Skirting and vent screens should be kept in good condition to prevent animal access and to maintain adequate ventilation year-round. Inadequate venting or blocked vents can lead to moisture build-up under the house, fostering wood rot and wood-destroying insects. Proper crawl space ventilation is calculated at one (1) square foot of free vent area should be provided for every one hundred and fifty (150) square feet of crawl space. Proper ventilation will help to control humidity and reduce the potential for rot. Crawl spaces should be vented to the building exterior.  One exception to the ventilation calculation of 1/150 square feet can be made. The total area of ventilation opening can be permitted to be reduced to one (1) square foot of free vent area for every one-thousand five hundred (1,500) of under-floor area, when the ground surface is treated with an approved vapor barrier material and one such ventilation opening is within three (3) feet of each corner of the building. An annual inspection of the crawl space is best left to a qualified inspector. If you must do it yourself, follow these safety tips. Always let someone knows where you will be, wear sturdy coveralls and a dust mask, carry a bright light and avoid contact with any electrical wiring. The crawl space should be clean and dry. Nothing should ever be stored in the crawl space. Before entering the crawl space, turn the interior water fixtures on at the sink/lavatories, tubs, and showers and flush each commode/toilet at least twice. (CAUTION: NEVER ENTER A CRAWL SPACE WITH STANDING WATER.) While under the house, look for evidence of animal and insect infestation, leaking plumbing, foundation movement and anything else unusual like damp or rotted wood in bath and kitchen areas. After completing your inspection, be sure that the access hatch cover is in good repair, fits the opening properly and is securely closed.