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Many atlanta subdivisions are mass graded. This means an undesirable building location(lots of steep grade are uneven lots) is transformed into individual flat or moderately sloped lots by movement of dirt. This usally includes removal of soil at hill(the cut lot),which which is them imported to other areas on site to create fill areas(the fill lot) or cut-fill areas(transitional lot).Cut lot tens to perform well since the soil is undisturbed where the hill was removed.Fill lot can compact more once the home is completed;this movement,however,is usually uniform and rarely cause distress th the home. These condition are consider when inspecting a home when built from mass graded lots. The homes soil,and foundation are in constant movement and forces fighting against one another.New homes may not give any indication of foundation issues for several years down the road.Although there are methods for inspectors to gauge that accurate standards were followed site prep,and adequate footing drains to help with hydrostatic pressure against the structures foundation.A strong foundation and proper lot drainage is the key to a stable foundation.In a perfect world every property would be built on the perfect lot,but as I know and you should as well this can not always be the chase.
A structure is expected to stand up. The force of gravity is constantly working to bring it down.A structure has to be designed to resist gravity.It must support its own weight,which is called DEADLOAD of the structure.It must also support the live load which are imposed open it,which include the people inside,the furniture,and other weight such as snow,and the materials used in the roof structure skeleton.
A structure does transfer its weight through the exterior walls,and load bearing partions to the foundation which in then transfers the weight to the soil through the footing.Not only is a structure expected to stand up, it is also expected to stand still. The structure movement is partially determined by the conditions of the soil support the structure,and proper drainage around the stucture.When the ground below the house fails,the house sinks.Soil moves. The foundation resists the pressure of the soil against the structure.Homes built on the proper site should be built strong enough to resist this natural pressure.
MOVEMENT:
The effects of settlement and movement on a home and their effects on the rest of the structure are not always obvious.While some signs are obvisous,other signs might need more in depth study to determine the cause of underlying issues.Wall cracks appear as the result of overloading or because of settlement or heaving. The location of the cracks can be a clue to what is going on to the foundation.
SOIL:
Is a dynamic system.Soil Moves.A house built on the bottom of a hill can have soil moving toward it over time and exerting more and more pressure against the foundation.It may be pushed from its original position.
WINDS
Plays an effective upon a structure.With heavy winds theres forces of pulling,and uplifting.Structures must be strong enough to resist these forces as well.
Vertical Cracks:
Are most often caused as a result of settlement of the structure,soilcompacting,or soil washing away under the footings.It occurs when there is an upward overload force next to a downwards overload force. They can also occur after remolding,when new dead loads are added to the structure,or by adding very heavy live loads.
Vertical cracks that extend down to the footings may be serious and should be investigated carefully. This could be cause by uneven settlement of the building and could indicate the wall is separating-one part settling more on one side of the crack than the other. The crack extending to the footing could also indicate a failure of material such deteriorating block,decayed mortar,or weak concrete,or improper construction standards.
Angled Cracks:
Appear when the upload and download force offset each other. They can appear when there is major difference in the soil under the home from one location to another,heaving of the soil,and resulting footing failure.Angled cracks can appear in pairs,where a load in one direction is offset by a pair of loads from other direction.When a crack is a single corner of the house,it can indicate a broken footing because of the soil underneath,expansive clay soilsor even the uplift from heavy tree roots in that location.
Horizontal Cracks:
On the foundation stem wall can indicate pressure being applied from the outside. The cause can be soil pressure against the wall,improper backfilling,and surface problems such as poor downspouts,Grade of lot,surface water drainage that allow water to pool around the foundation and increases the pressure pushing against the wall.When the wall is actually displaced-when the surface of the wall is out of alignment and the crack is wider on the inside face of the wall,serious problems can result.
There are other cause for horizontal cracks in foundation walls. There could be a vertical overload on the wall.Or the crack could be caused by settlement,where the wall has dropped when the soil underneath settled.
Internal Stresses:
The integrity of a structure depends on each individual structure members.A structure is in a constant state of Stress as individual member extert forces upon each other.For example,Floor joists spanning the structure would sag without the restraints and support provided by girders,which in turn push on supporting columns. These supoort systems must work in concert with each other without excerting more load to one another and resulting in damage.Structural member have two forces working on them at all times compression,and tension.Members of the structure has forces such as shearing,and bending.Individual members may fail under these stresses.A home inspection, the inspector looks for these underlying problems.
How to determine cracks in the foundation Settlement Cracks vs. Shrinkage Cracks .
I'm extensive traning and over 2000's of inspections in the atlanta area.EPA on site enviromental testing soil,lead,radon,mold.Experience & education is the key to sucesss in a changing field of new building codes,and material being introduce to the IBC.
**Leaking basements are a common problem.Generally,water problems in the basement are not dangerous to the homes occupants. It's predicted that almost all,about 98%,of basements will leak at some time during their life, and can be categorized as occurring during an catastrophic event such as flood,hurricanes,or broken plumbing.**
Probably about 90% of leaking basement are caused by surface water,and improper lot grade for storm water run off and footing drain problems
Controlling the surface water around a home is an important in maintaining a home. Surface water in refers to water introduced to the soil when it rains. The water, if not properly controlled, could lead to water penetration and result in damage to the structure, interior surfaces, and homeowners' belongings. In addition, hydrostatic pressure that is created when water accumulates next to or below a foundation may cause structural damage to the foundation. The best methods for controlling the surface water are contingent upon local weather patterns, the type of soil and the type of foundation the home has. However, the simplest method to properly divert water away from the property is to use gutters systems, combined with proper surface grading around the home.
Exterior Surface Grading
The grade or slope of the soil should be designed to direct water away from the home. Water accumulation next to the home can lead to water problems such as structural damage to wood framing, interior damage to finished surfaces and damage to the homeowners' belongings. Additional problems such as hydrostatic pressure against foundation walls or surface water mixing with expansive soils next to or under a foundation can lead to cracking of the slab and foundation walls. Proper grading is one of the easiest ways to manage surface water, reduce the possibility of water hydrostatic pressure, and control the water content in expansive soils.
Grading of the Soil Around the Perimeter of the Home
The soil around the perimeter of the home should slope away (at a minimum of six inches for the first 10 feet) from the house to prevent rain water from accumulating next to the foundation. Soil in this case does not refer to the topsoil but the layer of soil which directs the water away from the house. Many times the topsoil is porous (as would be used for planting) and absorbs the surface water.The overall lot grading is also an important concern since surface water may enter from adjacent properties. Generally, if the house is located on a slope or on a lot that receives water run-off, swales are often used to direct the water around the house. Swales are shallow ditches or depressions in the landscape that capture the water run-off. Then, like a small creek, the water is directed around and away from the house.
WET BASEMENT
A wet basement can be a nuisance or a real nightmare. Each year, thousands of homeowners are faced with the unpleasant side effects of seasonal rainfall. Problems they can face range from mere dampness to flooding. Chronic basement leakage is a serious problem that can destroy personal property, furnishings, appliances, and can sometimes cause permanent structural damage to a home's foundation. Excessive moisture is a huge attraction to wood-eating insects, wood rot and decay. Despite the pervasiveness of the problem, few homeowners are aware of the causes of wet basements.
Common Causes
A common cause of wet basements is improper surface drainage, such as a yard sloped toward the home. In many cases, the problem can be greatly alleviated by re-grading the yard to slope away from the homes foundation or diverting surface water around the house. Other common culprits include poorly positioned rain gutter downspouts, missing, leaking or clogged rain gutters. A downspout that is improperly positioned to drain against the side of the house, allows water to build up along the foundation wall, until the backed-up “reservoir” finds a weak spot in the foundation wall.
The most serious cause of basement leakage is a high water table. A high water table problem occurs when the home is built too deeply in the ground, into the level where water remains constant throughout the year. A high water table problem can also be caused by under ground springs or sustained periods of rainfall that cause the water table to rise during the wet seasons.
Is it Leakage or Condensation?
You should try to determine if your wet basement is the result of water “leaking” in or condensation forming on the cool surfaces. Condensation occurs when warm, humid air comes into contact with cooler basement walls, floors, water pipes etc. To illustrate, take a cold bottle of soda out of your refrigerator and sit it on the counter. After several minutes, you’ll notice steam forming on the outside of the bottle. After many minutes pass, you will see a small puddle of water forming at the base of the bottle, from the beads of moisture running down the bottle. The result is classic condensation, not “leakage”. If your basement is actually leaking, you should be able to locate the source of the leak in the form of a puddle or stream or water.
Helpful Tips
Your rain gutters should be cleaned of leaves and debris at least once per year. Downspouts should direct water runoff from the roof to a discharge point at least several feet away from the homes foundation. Use a splash block at the end of your downspout to avoid soil erosion. Never bury your downspout lines unless you can empty them out to daylight.
Consider buying a good dehumidifier to lower the natural humidity level in your basement. Make sure your dehumidifier is the proper size for your basement. Ask for a drain hose attachment so you don’t have to empty the water collected every day and get a unit with a built-in de-icer. Dehumidifiers are actually refrigeration coils and can freeze up and stop working. Keep the doors and windows to your basement closed, year round. Opened doors and windows allow extra humidity to enter your basement, causing condensation. Your dehumidifier will also run less.
Home settle caused be poor lot drainage.Water is the worst enemy to a foundation to a home.Settlement often happens when parts of a house drop below the elevation or height where they were placed during the original construction. There are numerous reasons why this may happen. The soil beneath the foundation or beneath column supports may shrink due to moisture loss. The soil may not have been compacted properly before the foundation was installed. Large pieces of organic material may have been included in the soil under the house. When it decays, the soil above it collapses to fill the void. The list of possibilities is nearly endless. Not all houses settle, but many suffer cracking of one type or another.
Cracks happen for all sorts of reasons. Different construction materials have different expansion and contraction coefficients, some materials change shape and size as they absorb water and water vapor while materials immediately adjacent to them do not budge.Understanding House Settling Cracks.If you have an understanding as to why cracks happen, then you can often work to make permanent repairs. There are some cracks that can't be easily repaired. What's more, it is hard to totally disguise some cracks. Large houses have joints within them. These are places where the house relieves movement, just like the joints in our fingers, arms and legs. I often see cracks in modern homes where columns support beams. You can see cracks right where the contact point between these two structural members meet.
Hardwood floor often develop cracks. There are all sorts of reasons for that to happen, and almost always they can be traced to a humidity or moisture problem.If you are getting ready to build a home, you need to realize that certain subdivisions are cut and fill operations. In other words, the developer takes dirt from one place and uses it for fill in other parts of the subdivision. If this soil is not placed with great care, it can settle! If you think that you are building on fill dirt, by all means spend the extra money to get it tested by a soil engineering firm. If you don't and you end up with problems.
Shallow Foundations
Many houses are built on slabs or have crawlspaces. The footers for these structures need to be placed just below the frost limit in the local area. The closer the frost line is to the surface (warmer climates) the greater chance you might have for droughts that cause your foundation to move. If you live in an area of clay soils and have seen a dried mud puddle with large cracks in it, then you have expansive clay soils in your area. Not only do these soils shrink sideways as they dry (this creates the cracks you see), but they also shrink down in volume. The shrinkage can be dramatic and can cause all sorts of cracking, door and window fit problems, etc. You can plan ahead and minimize foundation movement if you install water injection pipes next to the footer when you build the structure. I always did this on my jobs and it has given my clients the ability of tricking the soil under their houses and room additions into thinking it is raining up there on the surface!
The way you trick the soil is to install a four inch perforated pipe along the side or on top of the footer of the shallow foundation. You install one or two tee fittings in the piping so that you can extend a vertical riser pipe up to the surface. Install a loose fitting cap over this riser. When the drought hits, you simply let a garden hose run very slowly in the riser pipe for 24 hours or so. The pipe will evenly distribute the water around the footer if you have installed the footer fairly level. This system is simple and inexpensive to install and will save you hundreds of dollars in repairs and lots of headaches as well! If you try to fix a house that has cracks, talk with a structural engineer. If you pier one or more corners, you may create new stress points at other places!
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