Your Foundation – From the Ground Up
All things, metaphorically and literally, need a strong foundation to create a stable environment.In this article, we are talking about the literal type of foundations; those that hold up buildings, and in particular, homes. We will focus mainly on poured concrete foundations in homes that have a basement, as this is by far the most common type. It is our intent that you have a reliable general understanding of some of the issues that can impact it, and what you can do to minimize problems.
On any given plot of land, there will be an optimal location for the home's foundation; that piece of ground that meets municipal clearance requirements, provides adequate drainage, and meets your chosen aesthetic. This has all taken place before you choose to purchase a particular home. If the foundation installation is completed to a modern professional standard, the likelihood of water leaks to the interior is greatly reduced, but not necessarily eliminated.
Remember that at least a portion of your basement is underground.Concrete walls in direct contact with soil tend to stay cooler in the summer. This fact, combined with the more humid summer air, may lead to moisture condensing on the interior of the finished basement wall. This will encourage the development of potentially harmful mould and mildew. Two simple measures will reduce this likelihood:
- Operate a dehumidifier in the basement to collect moisture from the air.
- Paint your interior basement walls with a mildew resistant paint.
Cooler basements in the summer may also lead to pipes "sweating". This moisture is condensing on cold water pipes, sometimes to the extent that your basement may suffer water damage.Pipe insulation can eliminate this problem, it is readily available at most hardware stores, and it is very easy to install.
A properly installed foundation will have hidden drainage measures below the surface soil grade. These measures include weeping tile, crushed stone backfill and damp proofing.
When you buy a finished home, your home inspector will look to confirm that the finished soil grade at the perimeter walls slopes away from the house to aid in the drainage of surface water.
The proper installation of eavestroughs and downspout also plays an important role in maintaining a dry basement.These need to be kept clear of organic debris at least once a year. The best time to clean your eavestroughs and downspout is in autumn, after all the leaves have fallen. The downspouts should extend well away from the foundation (five feet) or, where applicable, be directed underground to your nearest storm drain.
Window wells are great at allowing light into a dark basement, but they need to be maintained.Collected leaves or debris should be removed in the fall to ensure proper drainage. Make sure the soil grade in the window well is at least 6" below the windowsill, to minimize the likelihood of water entry at that location. Also, keep them clear of ice and snow build-up.
When it is impossible to improve exterior drainage to the point of preventing leaks or seepage at the interior, the installation of a strategically placed basement sump pump can reduce the water pressure at the exterior. A professional plumber can help you identify a location and complete a proper installation.In most municipalities, rather than draining the sump pump discharge into the sewer system, the sump should drain to the exterior, well away from the foundation. Bear in mind that sump pumps are most frequently needed during large rain events; such events also coincide with conditions that are conducive to electrical power failure.Accordingly, it is smart to have a battery or other type of back-up system to ensure sump pump operation when you most need it.
PROBLEMS AND SOLUTIONS
After a long career as a professional home inspector, this author has seen almost every foundation problem imaginable.It has been rare to encounter catastrophic defects that would require a total re-build or expensive substantial repair.But it has been very common to encounter deficiencies that can cause leaky basements.Leaky basements can lead to the development of interior mould and rot and may negatively impact the health of the home's occupants.
As discussed above, poor control of exterior surface water will lead to excessive water pressure against your foundation.In that circumstance, there are a couple of ways that water may enter your basement.
Concrete, when cured, is brittle.When it cracks, the crack goes all the way through the wall, appearing on the inside and outside of the wall. There are several reasons why cracks may appear in a concrete foundation:
- The most common cause is shrinkage of the concrete as it cures over time. These cracks are typically vertical and run the entire height of the foundation wall. They are usually thin and not a structural concern but leaks to the interior will occur if there is water pressure at the exterior.
- Settling cracks typically occur if an underlying footing moves. The movement can happen if the footing is not properly supported by the ground upon which it rests, or if the concrete has not been properly reinforced with an adequate amount of steel rebar. These cracks tend to be diagonal, wide at the top and narrow at the bottom. There may or may not be some surface deflection. These cracks, especially if they appear early in the life of the foundation, can present a structural concern and they should be evaluated by a qualified technician to determine if mitigation is needed.
- Horizontal cracks, if they appear just below the exterior soil grade, are likely the result of frozen ground adhering to the concrete. The soil expands as it freezes and may put enough pressure on the concrete wall to cause a horizontal crack.Improving drainage at the exterior will eliminate future cracks.
- Pressure or impact cracks may occur as tree roots grow against the foundation wall, or when a large rock impacts the wall during the backfilling process. These cracks are usually "V" shaped.Again, evaluation by a qualified technician is recommended in these instances.
- Horizontal cracks located well below the soil grade also should be evaluated by a qualified technician. This is often the consequence of an installation failure, such as insufficient rebar or the wrong concrete mix.
Almost every concrete foundation has cracks; most of which do not pose a threat to the structural integrity of the home. Nevertheless, if there is water pressure against them, they will leak.Relatively narrow cracks, usually caused by the concrete shrinking or very minor settling can be repaired in a variety of ways. One of the best and least expensive solutions is to expose the crack at the interior of the basement and have a professional inject, under pressure, a flexible grout that will fill the crack its entire length and keep the water out. Other solutions can involve exposing the crack at the exterior and applying proper patching material. This involves some excavation and can be quite disruptive and costly. In every case, engage a professional to examine the crack and prescribe proper mitigation.
One other common deficiency is "honey combing". This occurs when there is a pocket of air trapped as the concrete cures.During installation of the concrete, a vibrating rod is used to eliminate air pockets.This must be done before the concrete begins to cure. If not properly vibrated, honey combing will appear at the wall surface when the foundation forms are dismantled.
If severe enough, some water seepage may occur.If that happens, a properly applied coat of epoxy can usually prevent future water entry.
There are many different types of foundations and materials used to build them. The subject of this article is the most used poured concrete foundation, but other types and materials, past and present, include concrete block, brick, cut stone, field stone, insulated concrete forms (ICF), preserved wood, pilings (wood, concrete, brick, steel), slab-on-grade – to name just some.
Let's review some key takeaways:
- When properly located and constructed, most concrete foundations will not leak.
- Even well-constructed foundations may experience shrinkage cracks.
- Most cracks can potentially leak if exterior grading and drainage are not well-managed.
- Proper rain eavestroughs maintenance and redirection of collected roof water are important measures to prevent basement leaks.
- Sump pump installation can reduce water pressure against the foundation and minimize or eliminate basement leaks and seepage.
- Most cracks that present with leakage can be repaired at a reasonable cost.
- When in doubt about the type of foundation damage and related consequences, contact a qualified technician to advise you.
A thorough professional home inspection before you purchase your home is your best chance to identify foundation related issues and discuss their implications. It is a visual inspection, so the possibility exists that deficiencies are below grade or concealed by finish materials at the interior. If you subsequently discover leaks that were not apparent during the home inspection, re-engage the home inspector to evaluate the situation and prescribe the best course of action. Find a CAHPI Home Inspector.