Typical Foundation Problems

Posted on 22. May, 2011 by in blog

After being in the foundation repair business for over 20 years, we just about seen it all.  Here is a list of the most common foundation problems we have seen over the years.

Most Common Problems With Brick Foundations
The two most common problems with brick foundations are the porosity of the brick (how much moisture a brick can absorb) and the ‘decay’ of the mortar. Both of these factors encourage damage through exposure to frost cycles and roots searching for moisture.

Most Common Problems with Block Foundations
Concrete blocks used in construction are normally hollow. If the mortar that connects the blocks degrades in any one area, it allows water to fill up the empty cavity of the block. It then travels into surrounding block cavities until the water finds a way out. Water would be able to exit either by evaporation through walls into the basement or through a joint that has an active leak.

Most Common Problems With Modern Poured Concrete Walls
There are significant differences between modern poured walls and walls constructed 80 years ago. Older walls were constructed in short lifts over a number of days using concrete mixed onsite and occasionally using materials found onsite. At that time, these techniques were acceptable though they do not enjoy the longevity of modern walls we see today. They often fail at the joint between the various lifts or within a particular lift that was not properly mixed or placed. Problems in modern poured walls almost always stem from improper techniques employed from workers onsite. It simply comes down to the abilities and attention to detail employed from the worker ‘holding the shovel’.

Cracks

Horizontal Cracks Near the Bottom of the Wall.   These types of cracks result from a great load or pressure being put on the foundation or wall from the side. The crack is an indication that there will be serious structural problems if not addressed from both the inside and outside of the basement. Generally the pressure in our area is due to hydrostatic pressure or frost. The symptom (the crack) can be easily fixed, but the cause is what should be fixed in this case. Pressure must be permanently released on the outside of the foundation wall and the wall may require structural reinforcement.

If you have horizontal cracks near the top of the wall it’s usually caused by Frost Pressure or Vehicle Loading.

If you have vertical cracks (Cracks Formed on a 45° Angle) are usually formed as a result of differential settlement. These cracks are quite common and differ depending on the size and ‘growth’ rate.  The main problem vertical cracks present is allowing water a direct route into the home.

Crack control joints
In terms of foundation walls, Control joints are planned vertical wall separations. Essentially they separate the wall into individual panels.  Should cracks occur it will encourage the concrete to crack in a planned pattern.  Failure to utilize control joints will allow the concrete to crack in less stable areas such as around windows and door openings.  This can cause further weakening and allow water an opening into the basement.

Bowing Walls
Bowing walls are the result of a great force pushing against the wall, such as frost or hydrostatic pressure. Basement walls typically begin to bow before cracks become visible. Any bowing at all is an indication of a weakened structure. Brick, block and concrete walls are equally as vulnerable to bowing and cracking. This is a serious issue that could cause major structural problems and must be dealt with immediately.

Surface Drainage / Grading
Proper and thought out surface drainage cannot be stressed enough. It is critical to keep as much surface water away from the foundation. This specifically includes downspouts. The city has promised to begin enforcing their 2010 downspout disconnection directive. As these downspouts are disconnected, it is critical that the collected water from a home’s roof is diverted away from a home’s foundation. Bear in mind that it is illegal to divert the water towards a neighbour’s property. No matter how well a home is waterproofed, it will not be able to sustain itself against a constant head of water pressing against it.

Vermin and Termites
In certain sectors of eastern Toronto, termites are prevalent. Subterranean dwelling, they do not necessarily require wood-soil contact. Unfortunately cracks and fissures within a foundation are sufficient for their entry into the home. Simply put above grade fissures and voids are also possible entry points to a home.

Downspouts
A home’s roof is a very large area that sheds all of its water. Gutters and downspouts are a major component of every home’s design, providing proper rain water drainage and diversion. If improperly placed, unmaintained or in disrepair, over time the consequences on your home’s foundation can be catastrophic.

Effloresence (Salt Damage)
Salt itself does not damage concrete, but it multiplies the amount of freeze-thaw cycles occurring. Salt carried into the concrete by moisture will attack any unprotected steel reinforcement within the material, causing the steel to rust, expand and break the concrete.

Leaks
Three things are required for a leak: water, a force moving the water in and a hole through which the water can pass. Removing any one of these three will stop the leak.  Types of forces: Gravity, Kinetic, Surface tension, capillary and pressure difference.  Holes can be visible or invisible to the naked eye.

Mould
Mould is naturally occurring everywhere. There are various types of mould, some which are benign and some of which are unhealthy to people, pets, and are capable of damaging wood and structure. Mould needs moisture to grow. Dry spells can cause mould to go dormant and then begin again with the onset of new moisture. This can appear that the mould came from ‘nowhere’. Removing the mould is a stop gap measure that does not actually solve the problem.

Spalling
Spalling is the deterioration of the surface of a brick or concrete. The main cause is usually water, either through repeated freeze-thaw cycles or from direct exposure such as downspouts. Deterioration can also be caused by: excessive vapour transmission traveling through the brick towards the outside, using a surface sealant that traps moisture behind the surface and thereby not allowing the brick to breath naturally through changes in weather, aggressive or frequent pressure washing and chemical cleaning may also lead to the deterioration of the outer shell thereby increasing the amount of water that the brick can absorb and hastening damage through freeze – thaw cycles. Once a brick or concrete begins to lose its surface integrity, the speed of deterioration will increase exponentially.

Concrete Deterioration
Though concrete is an excellent building material there are a number of different causes for its deterioration. The most common is frost cycles.

Alkali – aggregate deterioration by itself is not usually enough for structural failure, though it can be a strong contributing factor. It normally takes 5 to 10 years to manifest itself and is progressive. What happens is that the alkalis in cement (hydroxyl ions OH-) react with some types of aggregates within the concrete. The reaction forms micro cracks that allow water a clear route to penetrate the concrete and accelerate the severity of damage from the freeze-thaw cycle.

Radon
Radon is a naturally occurring radioactive gas whose origins begin with Uranium. The gas is omitted from the soil and can appear in basements, ground floors and on occasion, in ground water.
Air pressure inside your home is typically lower than pressure in the soil surrounding your home’s foundation. This variance in pressure can draw radon in through foundation cracks and other openings. Radon possesses a greater risk when entering your home via the soil, versus through your water supply.

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