Expansive soils, drainage problems
Carl Brahe
Damage from water is responsible for 85% of all money spent for home repairs in this country. Much of this damage is caused by uncontrolled runoff and misguided landscape irrigation. Nearly every home I inspect and Denver area has conditions where water outside is a potential danger to the foundation and structure of the house. Uncontrolled water from runoff or from misguided or damage irrigation systems also threaten sidewalks and driveways. Much of the damage caused by the uncontrolled water can be avoided by simple fixes.
Gutters and Downspouts
Rain and snow melt are ideally directed to gutters and delivered to the ground, away from the foundation. A high percentage of houses and commercial buildings fail this basic function. It is very common to find defective gutter and downspout systems that dump runoff next to the foundation. This can cause uneven swelling of expansive soils and may result in shifting and cracking foundations, sidewalks, driveways and parking lots next to the building.
Clogs, improper slope, poor installation or damage can allow water to run behind and cascade over the front of gutters. Extensive rotting of building materials, mold growth and infestation by insects may occur. When the water content in building materials exceeds 19% all of these conditions are likely to occur.
Clogged gutters, or gutters with improper slope, can send runoff water down the side of your house, into the attic or inside walls. Water can run from the highest level of your home to the lowest and to the farthest reaches. Look for water stains on the face of the gutters and on surrounding building materials that indicate water flowing over the front or behind gutters.
Missing, leaking or misdirected downspouts and extensions can crack foundation and worse. Make sure all downspouts and extensions are in place and in good repair. All downspouts need to be directed away from the foundation. Splash blocks, extensions and drain systems can be used.
Foundation
All foundations experience some movement. They settle initially after being built. Over time there is likely to be more settling. The whole foundation may rise and fall riding on the expanding and contacting soil. If one part moves independently, damage from foundation to roof may occur.
Foundations in areas with expansive soils are built to float on the soil as it expands and contracts. The foundation floats as a single unit on the swelling and receding soil like a ship on ocean waves. As long as the soil has a uniform amount of moisture around the whole structure, the rising and falling of the soil is fairly uniform.
Uneven moisture around the foundation can cause sections of the concrete to rise or fall independently instead of as a single unit. When this occurs parts of the foundation can be damaged or even fail.
You can check the moisture pattern around your foundation easily using an inexpensive house plant watering meter. This tool can be found in hardware and home improvement stores for less than $10.
Stick the prongs of the moisture meter as deeply into the earth as you can about a foot from your foundation. Record the moisture level and move a few yards in either direction. Retest then continue around your entire house. If you find differences in moisture content, take measures to drain the wettest areas to bring moisture content the levels of the driest area. If this is not possible, add water to the driest areas to bring them to the average moisture level. Do not water the foundation.
If there is extra moisture on one side of the house look for causes. Watch for clues like water stains or erosion that might lead you to the cause.
Look for cracking in the foundation. Small cracks may not threaten your foundation. Large cracks, ¼” or more, are always of concern. If in doubt call a structural engineer. Even small cracks may allow entry of insects or radon. Cracks should be sealed with an appropriate sealer. Ask at your local hardware or building supply.
** Always use products appropriate for the job at hand. Using the wrong products may cause additional damage. **
Sidewalks, Driveways and Parking Lots. Some expansive soil can grow to as much as 115% dry volume when wet. Expansive soil swells, growing in all directions as it absorbs water. When the ground dries it shrinks. Foundations, sidewalks, driveways and parking lots rise and fall with the water cycle.
Most damage to sidewalks, driveways and parking lots is the result of poor preparation of the bed beneath. A layer of crushed rock or gravel, properly compacted, provides support that compensates for movement of the soil beneath. It’s hard to repair the substrate but directing the flow of runoff and landscape water away from concrete/asphalt will help.
Sprinklers
Significant damage can occur from misguided watering of lawn, shrubs, flower boxes and gardens. Any event that directs water toward, or against your house is a danger to your foundation and may contribute to flooding in your basement. Oscillating sprinklers that spray against the house may damage siding, window and door frames, soffit and fascia, as well as the foundation.
Sprinklers next to foundations, sidewalks, driveways and parking lots can put water where it can cause movement of and damage to concrete and asphalt. They can create a flow of water through foundation, undermine concrete/asphalt and cause pad movement.
Any sprinkler that puts water in contact with the building, the earth next to foundation or concrete/asphalt pads should be repaired, replaced or capped off. Periodically check the aim of your sprinkler heads and notice where the water drains toward the foundation, sidewalks or driveways. If sprinklers are causing water to deposit to close to the house or sidewalks and driveways, re-aim or replace them.
More efficient sprinkler heads may be available. Soaker and dripper systems are inexpensive and efficient and may be easily installed by homeowners. These systems can save significant amounts of water.
A slowly dripping hose faucet leaks about 5 gallons of water per day into the ground next to your house. This can leak though the foundation walls. Look for signs of spalling on the inside of concrete.
Spalling is salts washed through the concrete that deposit on the inside as the water evaporates. It has a white, fuzzy appearance. If you have spalling, water has at sometime flowed through your foundation. This process can eventually cause rebar to rust losing all structural strength.
Water pressure can also build up behind the foundation wall causing it to crack horizontally and can cause it to fail.
Drainage
Proper grading can help. Water at the foundation should quickly drain away. Hard soil packed next to the foundation helps shed water. Underground drainage systems can be used where above ground drainage is not possible.
The soil level next to the house should be at least 6 inches below all wooden parts, like sill board, framing and siding. This helps prevent wood rot and entry of invaders like termites, ants and crickets.
Dirt should slope away from all sides of your foundation six inches in ten feet. When this is not possible a drainage system may be used to drain water away from the foundation. If concrete has settled sloping toward the foundation, concrete leveling may be used to repair it.
Grading at the foundation often directs water underneath sidewalks, driveways and parking lots. Contours can be formed so that runoff and excess irrigation water are directed away from concrete and asphalt. Underground drainage systems may be used, where contouring is not possible, to carry drainage to an appropriate place.
You may notice cracks in walls and ceilings. Doors and windows may stick. This may be the result of uneven moisture under your foundation. If water drains away from three sides of your house, but brings the water to the foundation on the other side, extensive damage to your foundation may result.
Summary Uncontrolled water can be a major threat to a property, especially where the soil is high in clay content. The most common sources of uncontrolled water outdoors are:
- problems with roof, gutters and downspouts that allow water to drain next to foundation or into or on to building materials
- grading problems – dirt should slope away from the foundation on all sides of the house
- grading problems are often hidden by landscaping features such as bark, or stones that hide spots where water runs to foundation or pools next to it
- brick, stone, plastic and metal edging next to house creates areas where water pools
- uncontrolled watering
- moveable sprinklers that cause water to hit foundation, house, or pool next to foundation
- sprinkler systems installed with sprinkler heads too close to foundation or aimed in a way that hits house or puts water too close to structure
- uncontrolled moisture can cause
- wood rot
- mold growth
- delamination/deterioration of building materials
- conditions friendly to insects, spiders, reptiles and rodents
- damage to foundation and structure
- damage to concrete and asphalt
- erosion
A building can stand strong and secure for hundreds of years and yet can quickly be severely damaged by the good intentions and hard work of property owners and their contractors. A misplaced or improper sprinkler head, a damaged or poorly designed gutter and downspout system, misguided drainage, or many other conditions easily corrected or avoided can extensively damage a structure in a very short time.