: Helpful Advice If You Encounter a Bowing Foundation Wall

By Aaron J. Stull
Owner/President – Keystone Basement Systems, Inc.
AStull@keystonebasementsystems.com

Wall anchor and steel I-Beam reinforcement methods have a multitude of specialized applications.  Furthermore, other viable foundation reinforcement methods exist and are used commercially every day.  For the purpose of this article I am only going to focus on steel I-Beam reinforcement and wall anchoring in situations where inward bowing of an exterior foundation wall has been observed.  This type of movement represents the bulk of residential problems encountered by foundation repair companies.  For the purpose of this article I will use generalities and note that specific circumstances may call for a specific repair plan.  Moreover, I will assume that the readers of this article are somewhat familiar with what both reinforcement methods are.

In my experience with residential foundation repair I can agree to one definitive fact.  Fact is that no one method works for all situations.  Furthermore, it is my strong belief that all viable methods should be considered when designing a foundation repair plan.  Because every home has different conditions and situations, utilizing this methodology will ensure that the most cost-effective and successful method will be proposed to the property owner.

I order to determine a method of correction, we should first consider the following variables -

1. Foundation Type
2. Fill Height
3. Fill Type
4. Wall Height/Length
5. Wall Width
6. Nature of Wall Deflection
7. Anomalies

Foundation Type:

Western Pennsylvania, where my business is located, is home to a diverse collection of foundation types.  The foundation types that are usually seen are of poured concrete, stone, block (Cement or Cinder), Terra Cotta, brick or a combination of each.  In addition to the type, it would be good practice to observe the general condition of the foundation.  Examining these facts will begin to shed light on some situations.  For example, if you were to encounter a terra cotta foundation that was in very poor condition with a measurable inward deflection of 6 inches, it would be wise to forget either wall anchors or I-Beams as the wall should be rebuilt.

Fill Height:

Fill height, in respect to wall height and all other variables, is important to note as it is usually the main force acting laterally on the foundation wall.  Typically the higher the fill height the greater the lateral surcharge the soil will place on the wall.

Fill Type:

Fill type should be looked at to understand the amount of pressure per cubic foot of earth on the wall.  Because different material has different weight, particle size, shape and other important aspects, it is wise to understand how each acts on a foundation.  Moreover, the rate in which water moves through a material is important as water can add additional hydrostatic pressure if it cannot pass quickly through the soil that rests against the foundation.

Wall Height and Length:

Wall height is imperative to review.  Generally, the taller a wall, lesser is its ability to resist lateral loads.  Structural damage is merely the result of a wall that is built too high without adequate internal reinforcement or wall width.

Wall length is important to note in determining the reinforcement plan for a home as well.  In some cases you will find that a wall span is too long and without buttresses which has allowed the wall to bow and crack.  This would be considered in many cases to be a design flaw.

Wall Width:

The width of a wall is also important as the wider the wall the greater the ability to resist lateral loads.  Many contractors use blocks that are 8” wide in situations that call for 10” or 12” walls.  Also, a plan may call for a wall width of a certain size and additional internal reinforcement in the form of rebar and concrete.  If this is not done the wall may acquiesce to pressure.

Nature of Wall Deflection:

In my opinion this is the most important variable to consider.  Not all wall deflections are the same.  Although there are many variations, three main types exist.  Some slip at the top usually due to poor top attachment and lateral pressure.  Some slip between the first and second coarse (In Block Foundations) inward.  This is usually from a greater lateral load in respect to the amount of compressive weight from the structure above.  The third is the wall that bows in the middle from increased pressure.  Each must be treated differently as they are all representations of pressure being translated differently based on the overall structure and configuration of the home.  Walls slipping at the top generally need a reinforcement method that incorporates a new top attachment for the home.  Walls “slipping” at the base can be reinforced with a method that integrates internally into the floor and buttresses the wall (Please note that a wall that has slipped more than 25% inward in respect to the wall width should be rebuilt).  Walls that bow in the middle are usually the easiest to correct with reinforcement methods.

The method I use for most reinforcement projects, when the inward movement of the foundation wall is more than two inches off perpendicular, is Steel I-Beam buttressing.  I simply do not prefer wall anchoring in most situations, as I have seen multiple cases where walls continues to move in around the inner reinforcement plate (standard inner plate measuring 12” x 18”). Furthermore, I am a firm believer in simplicity for design.  Wall anchors are predicated on several things being “normal” such as soil type and composition around the home, obstructions or rocks not being present or the distance from fill material that was disturbed while building the home to virgin soil that was not disturbed.  At one time I used wall anchors extensively until I had some issues with the quality of their performance.  Moreover, some cases require the homeowner to periodically tighten down the inner anchor bolt which can sometimes be done incorrectly or not done at all.

The wall anchoring process involves a lot of steps to achieve success.  Thus, I use them very sparingly.  I understand that this statement seems bold to many in this industry, but I feel that simplicity in design, with as few steps or assumptions as possible is usually the better choice.  Please understand that I do think wall anchors have a place in the industry. When installed correctly, and at the appropriate anchoring distance and frequency, wall anchors are a great corrective measure for retaining walls, sea walls and various stairwell situations.  But when discussing inward deflection of a primary foundation wall I feel that they are not as effective as steel I-Beam buttresses.

The method that I have preferred for the last 6 years has proven to be dependable and cost effective for the homeowner.

   I would first place a custom order for a steel I-Beam that is three feet longer than the wall being reinforced.
   In addition, the size of the steel (4×4, 4×6, certain pounds per foot, etc.) would be based on conditions with the building.
   In residential applications I would usually space the beams 5 feet on center (Although this can be altered for different situations) perpendicular to the wall.
  I would dig a hole in the floor that would act as the beam pocket and countersink the beam three feet into the ground and fill the hole with concrete.
  Then, I will create a custom top attachment utilizing no less than 16 3/8th lag screws at 3” in length.  I would create a situation where the top of the beam is locked into place by wooden members attached by lag screws so that the pressure at the top is translated to 16-24 lag screws and at minimum 4 floor joists.  This will allow for a safe transfer of pressure and prevent cracking and floor joists.

In closing, I cannot stress how important it is to have a qualified expert design a repair plan for your foundation needs.  All situations are different and there is no technology that works in all situations.  If you think you have a problem, and would like to have it evaluated, give us a call at 800-771-3244 and we would be happy to help.

Please note that the above advice was given as a general rule of thumb.  All situations should be reviewed by an engineer to verify that the correct method is being used.

“Keystone Basement Systems, Inc. is a foundation repair company. KBS is not, however, a engineering firm and should not be considered as such.”