Constructing a Retaining Wall on Sliding Soils

Posted in: ENGINEERING-DESIGN, Allan Block, Wall Failures
The old retaining wall (which failed) was constructed on soils that were sliding downhill!  The rock was too deep to put the new retaining wall on the bedrock, so we drilled piers down to the bedrock to stop the hill from sliding and to support the new retaining wall.

This video shows you how to prevent a retaining wall failure when there are sliding soils!


Link to Photos of this project
Joseph Kowalski, P.E.
Current State PE Registrations

Tiered or Merged Retaining Walls?

When one retaining wall is constructed above another retaining wall, the two walls together are called a Tiered Wall System.  Tiered walls look like this:

When dealing with tiered walls, a retaining wall contractor will ask:
  1. How far apart are the walls?
  2. How high are the walls?
  3. Are they really two separate, independent walls?
  4. Do the two tiers of wall join and become one (merged) wall?                      
                                                                                  READ MORE ...

Retaining Wall Block Tolerance

Posted in: BLOCKS
This short article discusses retaining wall block tolerance: what it is, what are the limits, and what happens when blocks are manufactured "out of tolerance".

Segmental retaining wall blocks do not use mortar.  They are simply stacked one upon another.  Sometimes there are grooves, or lips, or pins or clips that align the blocks.  However, the blocks always rest one upon another.

Our past videos (like this one) and articles discuss the critical importance of getting your first row of blocks perfectly level.  The blocks must be level front-to-rear and side-to-side.  A perfectly level first-row of blocks will help make wall construction fast!   Unless .... the blocks are out of tolerance!

When blocks are "out of tolerance" it means that one side of the block is higher or lower than the other side.  You can see that this can cause big problems for these reasons ... Read More...

Stone Strong Retaining Wall Installation

Posted in: Stone Strong, How-To Videos

Retaining Wall Design Contracts

Posted in: ENGINEERING-DESIGN, Homepage

Obviously, retaining wall design involves contracts.  These contracts between the Engineer and the Client are important.  Does the contract benefit both parties?  Is using contracts a win-win? 

Contracts are important to:

1.    Memorialize everyone's understanding of each party's roles and responsibilities;

2.    Reach a mutual understanding of the project requirements;

3.    Establish the rules to which the parties will adhere; and,

4.    To identify and allocate risk fairly.

 A good contract fairly allocates reasonable risk to both parties, based on the benefits of the project to each party.

Here's an example of fair allocation of reasonable risk:  when the contract includes a Limitation of Liability for the Engineer.  Why, you might ask, am I limiting the Engineer's liability and how is that fair?

Well, here's how it is fair:  The Engineer doesn't demand an Unlimited Fee.  With an unlimited fee comes unlimited liability.  With a limited fee there is limited liability.

Sounds fair to me.  What do you think?

Why did I run across Tennessee? (twice)

Posted in: CONTACT US

314 miles.

100 degrees Fahrenheit.

 Outrageous humidity.

Steep mountains.

Trucks roaring by.

 Feet pounding the hot asphalt for more than a week.

 Why would anyone want to run all the way across Tennessee in July?!?


Boston Strong



Joseph Kowalski, P.E.

Current State PE Registrations


Posted in: SmartSlope
SmartSlope Living Wall

Every once in a while, a truly fantastic product comes along.  SmartSlope is one of those products!  The benefits include: excellent block dimension tolerance, a 100% mechanical connection to the reinforcement, a huge pocket for holding soils, the ability to batter at 20 degrees or flatter, and the ability to install drip irrigation lines directly into the block!

Here's a video about the system:

So, we are talking about the Living Wall: the most environment-friendly block on the market and the only block with a true 100% mechanical, verifiable connection.

For more info see

Retaining Walls: What is Global Stability?

Global Stability is the stability of the hillside ABOVE and BELOW a retaining wall.  By it's very existence, a retaining wall changes the shape of a hillside.  These changes should be addressed by the Engineer and Contractor to determine if the hillside is stable.  Take a look at these sketches, photos and video:




Retaining Wall Failure and Rebuild 6041

Posted in: Wall Failures
Retaining Wall Failure: upper portion collapsed
When this 38-foot high retaining wall failed, Kowalski Engineering was retained to help.  Our services included determining what caused the failure, redesigning the new retaining wall, and reviewing the new wall's construction.

Many of the retaining wall blocks were reused on the project - demonstrating that these blocks are extremely durable, even after being dislodged from such a height.  You see, the large and durable block facing was not the problem.

Retaining Wall Failure: upper portion collapsed
The problems were: the type of soil used during construction, the spacing of the geogrids, and (you guessed it) water.  Remember this recipe for failure: "Just Add Water".

Good design and good construction will account for the "added water" and a retaining wall will be quite stable.  We engineered the new retaining wall and reviewed its construction.
Retaining Wall Rebuilt


View Retaining Wall Expert Projects Map in a larger map

Failing Retaining Wall Pushing Building

Posted in: Wall Failures
In Cincinnati, Ohio we have our fair share of retaining wall failures: due to poor construction, poor design, or sometimes just age!  In this case, a number of factors contribute to a failing retaining wall that is literally shoving a building sideways!

Photo of failing old stone retaining wall pushing building sideways!
At this location, a natural stone retaining wall was constructed outside an apartment building.  The foundation walls of the apartment building and this stone retaining wall are supporting the land adjacent to them.

However, at some point in the past another retaining wall was added above!  This additional retaining wall was constructed just a few feet away from the apartment building.  The nearby wall is about 6 feet high, and adds a huge amount of loading to the basement/foundation wall and to the natural stone wall.

The basement wall is being held in place at the front of the building and at the middle of the building, because there are walls at a 90-degree angle to the basement wall.  Those walls are supporting the basement wall.

However, at the rear, where there are openings for the garage doors, there is little support.  The top of the garage doors has been shifted a few INCHES sideways, and the back wall of the apartment building is bulging outward.  Even the old stone wall is being pushed outward.

The owner is currently exploring options for repair!