How to Identify Foundation Problems

Even though it does not look like it, the ground is in constant motion. Due to this fact, it is possible for your house to either settle or heave. If this happens, there are a few things you can look for, both indoor and outdoor, to help you diagnose the problem. Many times the problems caused by settlement or heaving is cosmetic and does not impede with the structure strength of your house. However, in some cases, it is necessary to fix the foundation problem.

Instructions

1. • 1
     Walk around the exterior of your house. Look for any cracks in the brick or mortar of the outside wall. Pay attention to the exposed grade beam as well to see if there is any cracking.
   • 2
     Close your garage door. Inspect the section of ground the garage door is touching. Look for any gaps on both sides of the garage door.
   • 3
     Go inside your house and inspect the sheet rock drywall for any cracking. Open and close doors and windows to see if they get stuck. Look at the corners to see if there is any cracking.
   • 4
     Walk slowly along the floors of your home, in socks or bare feet. Feel for any raised or sunken areas in the flooring. Look for any cracks in the cement slab on the basement floor.
   • 5
     Look at the upper portion of your kitchen cabinets, where the cabinet touches the ceiling. See if there are any gaps or cracks forming.

Two Broad Categories of Building Foundation Types

Category Definition

A foundation is the base of a structure or building. It is the part that provides support to the overall load of the building and prevents over-settlement or movement of the finished structure. Foundations spread out the overall weight to do this. Although there are several types of foundations, most can be broadly classed as either deep or shallow.

1. • Shallow foundations, or spread footings, are built close to the surface. If ground conditions will not affect the load-bearing capacity of the footing, then shallow footings are used. Shallow foundations include pads, strip footings and rafts.

     Deep foundations are built below the ground, at depths of 9 feet or more. This type of foundation transfers the load below ground to a more suitable material if the soil at the building site is unable to support it. Types of deep foundations include piles and caissons.

   Shallow Foundation Types

   • Pad foundations might be circular, square or rectangular pads, used to support a specific point load such as a column. Typically pad foundations are made of a block or slab that may be stepped if the load must be spread from a heavy column. They are usually shallow, but deep pad foundations can also be used. Strip foundations support a line of loads such as a wall or a row of columns placed too close to use individual pads. Raft foundations spread the load from a structure over a large area and are used when structural loads such as columns are too close together to use pads. Raft foundations consist of a concrete slab that covers the entire building area and may be reinforced by ribs or beams.

   Deep Foundation Types

   • Piles shift foundation loads through the soil to deeper soil or rock. They're used when it is beneficial because of cost or soil conditions to transmit loads beyond the depth of a shallow foundation. Piles are also used to support loads in regions where extreme weather such as high wind or rain would affect the foundation's load-bearing ability and are classed as end-bearing, friction, settlement-reducing, tension and laterally loaded piles. Caissons are made above ground and then sunk below ground by removing the material from inside the caisson.

   Foundation Selection Criteria

   • The type of foundation used for any given structure will depend on a variety of elements. Location, climate, soil and the purpose of the structure play a vital part in the type of foundation used. When deciding on a deep or shallow foundation, a number of engineering factors are also considered. The builders must consider the type of load transfer needed, the quality of soil at the building site and the weight of the building when complete, as well as the predicted limits of movement over time. If the load-bearing capacity of the soil is high and the soil is very dense, then settlement isn't as much of a concern as when the soil is loose. A shallow foundation would be suitable in this case. Shallow foundations are often used for residential buildings. Deep foundations are used when soil is loose or will shift under heavy loads. These foundations are commonly used in coastal areas or building sites with sloped ground.

Types of Foundation Settlement

1. • 
     Tower of Pisa: an extreme example of foundation settlement

     Foundation settlement is the shifting of the foundation (and the structure built upon it) into the soil. This can cause damage to the structure. Whether the soil is moist or dry is central to predicting the amount of settlement to expect in a given foundation. Areas with moist soils will have more foundation settlement than dry areas. The idea is that as water is squeezed out from the soil, the structure will shift according to the empty spaces the water left. The more water, the more shift.

   Immediate Settlement

   • Immediate settlement concerns the initial pressure on the soil under and surrounding the foundation. It is "immediate" because it occurs during and right after construction. It has nothing to do with water displacement, but is merely caused by the weight of the structure. In terms of building foundations, immediate settlement is relatively easy to predict and measure. In many cases, given the nature of the soil, foundations are constructed with the ability to withstand a certain amount of shift without damage. Damage usually occurs only in the long term, as the shift slowly continues over time.

   Consolidation

   • Consolidation settlement is distinguished from immediate settlement both by the duration of the settlement and by displacement of water. Consolidation is the more worrisome form of settlement because it is difficult to predict over months or years. Consolidation settlement is the settling of a foundation, over time, due to pressure exerted by the structure and squeezes out the water content of the soil, thus compressing it. Expulsion of moisture from the soil usually is a long-term process.

   Primary and Secondary Consolidation

   • Consolidation settlement has two components, primary and secondary. The former deals explicitly with the settlement caused by soil moisture displacement, and the latter deals with the elastic settlement after all movable water has been squeezed out of the soil. Primary consolidation is the most significant and potentially harmful of the two. Primary consolidation takes quite a bit of time, from weeks to years. Secondary consolidation is the quicker result of primary consolidation. Once primary has been completed, and all movable water has been moved, secondary kicks in. Secondary consolidation occurs immediately after primary, and takes far less time to complete. After secondary consolidation is complete, the structure remains in its permanent position. As a result, many builders advise residents in new homes to avoid repairing any settlement damage until secondary consolidation is complete, which is normally after two years at most

How to Prevent Soil Settlement

Soil is the ultimate foundation, serving as the base for all structures on earth. If that wasn't a big enough job, soil is also responsible for growing all the food needed to sustain life on the planet. The quality of soil varies by geographic location, with loam (an even mixture of sand, silt and clay sized particles) being the most desirable. Soil settlement, also called soil consolidation, occurs when applied pressure causes soil molecules to press tightly together. Water has a hard time traveling through this soil, leading to cracks in building foundations and low crop yields.

Instructions

1. • 1
     Reduce all unnecessary travel over the soil. If you use heavy equipment, set all tires at the same width so there is only one path for machine travel. Take fewer trips by managing your time; do your duties in one trip. Do not overfill your tires, but rather keep them minimally inflated.
   • 2
     Till at a different depth each year with sharp blades on thoroughly dry soil. Avoid tilling, or otherwise subsoiling, when the soil is wet. When you move wet soil around it tends to stick together, sealing the surface from future water absorption. This accelerates the rate of erosion, which also leads to soil settlement over time.
   • 3
     Control erosion further by changing the landscape. Plant various species of grasses along sloped waterways so the water has a path to follow. Plant grasses or trees in rows along the borders of your fields; they will act as a barrier for escaping soil and nutrient water.
   • 4
     Plant your field to accommodate the landscape across the natural slope of the land. You can build dirt ridges between rows to keep the soil from settling.
   • 5
     Avoid building structures on soils with a high percentage of clay. When exposed to water, clay expands and collapses, with the resulting soil settlement leading to cracks in the foundation of buildings.

What Causes Basement Wall Failure?

Improper Drainage

Poor slope or drainage around a building causes surface water to drain away slowly, thereby increasing water infiltration next to the foundation.  Increased soil moisture conditions increase hydrostatic (water) pressures on basement walls.  If the combined hydrostatic pressure and earth pressure (pressure exerted by the surrounding soil) on the wall exceed the wall's design capacity, the wall will crack, bow, lean, or shear.

Expansive Clays

Clay soils are considered expansive when they have the capacity for extreme volume changes with fluctuations in water content.  In short, expansive clays swell when wetted and shrink when dried.  Expansive, swelling clays against basement walls can exert lateral pressures on the walls of the magnitude of several tons per square foot! 

Foundation Wall Cracks

Foundation wall cracks can easily get worse if they're left untreated, especially in the case of cinder block wall foundations.  Any crack or opening in the foundation at all can become a passageway for water to enter into the home.  Additionally, because the foundation wall is literally cracked through, the gap will continue to worsen as the walls move and become influenced by pressure from outside the walls.  One crack in the foundation walls will lead to another, and no crack will ever improve on its own.  All cracks should be repaired if they're allowing water through, and even a hairline crack can be evidence of a larger problem and should be inspected by a professional immediately.

Horizontal Foundation Wall Cracks

Horizontal foundation wall cracks are potentially very serious problems that can sometimes lead to the complete failure of the foundation walls. These cracks occur when pressure builds against the side walls and forces them inwards. Given time, this pressure can snap the walls, creating an enormous and devastating problem. If you detect any crack like this, you should call Foundation Supportworks for a free foundation estimate. Many options are available for all foundation problems such as wall anchors, and crawl space support beams that will competently repair your wall, contribute strength, and help prevent the inward movement of the walls, redistributing the weight to where the load can be better handled.

Foundation Wall and Basement Wall Repair

Cracked, bowed or leaning foundation walls, are signs that you may be in need a basement wall repair that will stabilize your basement wall and keep it from getting any worse.

Basement wall repair is the expertise of Foundation Supportworks and our network of basement wall repair contractors.  Foundation Supportworks’ network of trained and certified contractors have consulted with literally thousands of engineers, architects, home inspectors, building departments and homeowners who are dealing with a failing basement or retaining wall. 

Basement wall repair is something we deal with every day, and you can be confident that our certified inspectors will properly diagnose your basement wall problem and recommend a solution that will work for you. 

Basement and Foundation Wall Repair Methods

There are several common basement wall repair methods available, and your Foundation Supportworks representative will explain them all to you, so that you can choose the system that will work best in your home. 

Some common basement wall repair methods include wall anchors, I-beams or wall reinforcement beams, carbon fiber straps, andhelical anchors.  Each of these options can be an effective basement wall repair solution, which is why it is important that you have an inspection done by a well-trained foundation repair contractor that will recommend the right solution for the situation in your home. 

Bowing Basement Wall Symptoms

Symptoms of a bowing basement wall can vary depending on the type of construction. 

Symptoms of bowing basement walls with a block foundation can include horizontal cracks in mortar joints, stair-step cracks at outside corners, horizontal shearing at the bottom of the wall and tipping at the top of the wall.  In some extreme cases you may witness more than one or all of these symptoms and may even notice basement walls that are bulging and have cracks all throughout the wall.  If this is the case, the wall may be on the verge of a collapse. 

Symptoms of a bowing or leaning wall with a poured foundation most often include the tipping of the wall, diagonal cracks at outside corners, and vertical or horizontal cracks in the wall.

What Causes Foundation Settlement?

The causes of foundation settlement are rarely due to the design (or under-design) of the structure itself. More commonly, damage is caused as changes occur within the foundation soils that surround and support the structure. The following paragraphs are brief explanations for a few of the more common causes of foundation settlement.

Weak Bearing Soils

Some soils are simply not capable of supporting the weight or bearing pressure exerted by a building's foundation. As a result, the footings press or sink into the soft soils, similar in theory to how a person standing in mud sinks into soft, wet clay. In such cases, footings may be designed to spread the load over the weak soils, thereby reducing potential foundation settlement. However, the majority of settlement problems caused by weak bearing soils occur in residential construction, where the footings are designed based upon general guidelines and not site-specific soil information.

Poor Compaction

Placement of fill soils is common practice in the development of both commercial and residential subdivisions. In general, hilltops are cut down and valleys are filled in order to create buildable lots. Properly placed and compacted fill soils can provide adequate support for foundations. When fill soils are not adequately compacted, they can compress under a foundation load resulting in settlement of the structure.

Changes in Moisture Content

Extreme changes in moisture content within foundation soils can result in damaging settlement. Excess moisture can saturate foundation soils, which often leads to softening or weakening of clays and silts. The reduced ability of the soil to support the load results in foundation settlement. Increased moisture within foundation soils is often a consequence of poor surface drainage around the structure, leaks in water lines or plumbing, or a raised groundwater table.

Soils with high clay contents also have a tendency to shrink with loss of moisture. As clay soils dry out, they shrink or contract, resulting in a general decrease in soil volume. Therefore, settlement damage is often observed in a structure supported on dried-out soil. Drying of foundation soils is commonly caused by extensive drought-like conditions, maturing trees and vegetation (see next section), and leaking subfloor heating, ventilation, and air conditioning (HVAC) systems.

Maturing Trees and Vegetation

Maturing trees, bushes and other vegetation in close proximity to a home or building are a common cause of settlement. As trees and other vegetation mature, their demand for water also grows. The root systems continually expand and can draw moisture from the soil beneath the foundation. Again, clay-rich soils shrink as they lose moisture, resulting in settlement of overlying structures. Many home and building owners often state that they did not have a settlement problem until decades after the structure was built. This time frame coincides with the maturation and growth of the trees and vegetation.

Foundations closer to the surface are more often affected by soil dehydration due to tree roots than are deep, basement level foundations. As a general rule, the diameter of a tree's root system is at least as large as the tree's canopy.

Soil Consolidation

Consolidation occurs when the weight of a structure or newly-placed fill soils compress lower, weak clayey soils. The applied load forces water out of the clay soils allowing the individual soil particles to become more densely spaced. Consolidation results in downward movement or settlement of overlying structures