August 28, 2015

Retaining Walls on Pluto?

Mountain Range on Pluto
The NASA probe, New Horizons has already taught us a lot since reaching Pluto. One thing we already knew was that Pluto was very, very cold (about 375-400 degrees below zero!). What we have recently discovered is a mountain range along Pluto’s equator. While retaining walls on the mountains of Pluto may still be in the distant future, you can bet when the time comes, Allan Block will be there!

Back here on Earth, there are some very cold places that are in need of or already use retaining walls to change the way we use the land. If you are living in one of these sub-zeros or maybe even just mildly freezing places, there are a few items to be aware of when building walls to last.

A prime example would be a retaining wall with a walkway above or a stairway through it.  When the weather turns cold, ice can form and make these areas very slippery. And since no one want to take a tumble, the natural instinct is to reach for the bag of salt and spread it around right?


The problem is Concrete’s enemy is Salt.   Salt over time has the ability to erode away the surface of concrete and degrade it overtime.  If too much salt is applied to a concrete wall, it can literally eat the concrete way, leaving a very messy and unstable wall.

So what can you do to preserve your beautiful wall and have a safe, non-slippery walking surface?  Use our friend Sand. Sand is course and will help provide traction with eroding the concrete blocks. While we might not be ready to tackle the dwarf-planet just yet, we can work to keep salt away from our walls and our backsides off the ice!

For more information on building retaining walls, visit our website at

August 21, 2015

Dirty Concrete? What to do When Your Retaining Wall Needs a Cleaning

Concrete block retaining walls look great and add a lot of appeal to your landscape.  But over time they can become dull and dirty, as organic materials become lodged in the crevices.  If you are noticing that dirt, mildew or some other unwanted substance has taken over your once beautiful wall, then it’s time to get out the garden hose and give the wall a good cleaning.  

You may be tempted to pull out the big guns and attack the problem with a power washer.  However, a spray attachment to your garden hose and a little dish soap will usually do the trick.  In most cases this will clean the wall and make it look new again.  If there are stubborn stains that resist the garden hose approach, you may need to power wash.  When using a power washer, make sure to use the broadest, lowest-pressure nozzle that will clean the surface.  A nozzle that is too narrow may cut into the block, causing irreparable damage.  Also, hold the wand at the correct distance to deliver the necessary pressure without damaging the block.

While dish soap will clean most walls, sometimes stronger cleaning detergents may needed where stains are not water soluble, or are caused by air pollutants.  There are many products available, and local wall suppliers can recommend a detergent that is safe for concrete products. (Find one near you)  Read the labels and be sure to protect any plants that you don't want damaged.

 Learn more with this downloadable sheet on caring for your retaining wall (download) or visit our website at

August 14, 2015

How Does Geogrid Reinforcement Actually Work?

From building a simple wall that is 3-feet (0.9m) in height to walls that are over 50 ft (15.3m), we put a lot of faith in these layers of geogrid reinforcements that are installed in and behind the Allan Block units.  So how do they do it?  The answer lies in how the soil interacts with the geogrid.

The Chinese were on to something when they were building the Great Wall of China.  As the stacked the dirt the realized that as the pile grew higher it also grew wider.  They needed a way to hold the dirt in place as it was stacked higher.  They used Tamarisk branches to hold everything together like you see roots do for a living tree.  The dirt gets trapped in the opening and cannot move.  Obviously, we have evolved from using branches and now have manufactured geogrid reinforcement to serve the purpose, but the concept is still that same.  The dirt gets trapped in the opening of the geogrid and cannot move.  By placing multiple layers of geogrid behind the wall it hold the entire area together as one structure.  We refer that to a composite mass consisting of block, rock and soil all held together by the geogrid reinforcement. 

So the concept is simple.  The longer your geogrid layers the more mass you have in your structure. Therefore, when you have that tall retaining wall the layers of geogrid are longer to withstand the increased pressure due to the height.  There is a great video here that explains how the concept works.

For more infomation on geogrid or other reinforcement options, visit our website at 

August 7, 2015

Why Mortarless Construction?

Why would anyone want to build a 4-foot (3.05 m) retaining wall or even a 30-foot (9.1 m) retaining wall without mortar?  A better question is:  Why not?

What is Mortarless Construction?

Mortarless construction is a method of building structures without the limits of mortar.  Simply stacking concrete block or stones has proven to be a durable and flexible alternative to creating amazing structures.  To learn more, visit our Built-In Engineering page on the Allan Block website.

Brief History of Mortarless Construction

Mortarless construction is not a new concept; one of the most commonly cited examples of constructing without mortar are the Great Pyramids in Egypt.  Although this accomplishment is hard to beat, the Inca’s craftsmanship in South America is a great example of architecture and mastery of mortarless construction.  A remarkable portion of what they built is still in use.  Even more remarkable is this is a seismic region!  Retaining walls and other structures the Inca built over 500-years ago have survived many earthquakes, while modern day buildings topple.  From the terraced walls in the mountains, to walls in Cusco supporting important present day buildings, their achievements have stood the test of time.  

Why Use a Dry Stacking System?

A dry stacking, mortarless system has many advantages over other construction methods.  Among these advantages are a flexible system with potential for unmatched site adaptability and being able to use a labor force that does not rely on masonry experience and skills.  By reviewing these advantages you can see how the overall project cost could be reduced.

  • Site Adaptability – A retaining wall constructed using a segmental retaining wall (SRW) block such as Allan Block, conforms to site your conditions with ease.
    • Frost – No need to build or design your retaining walls or landscape walls below frost depth.  The system is flexible meaning the wall will not crack like a rigid retaining wall would.  Also, your overall construction cost will be reduced in labor and materials because you are not burying unnecessary block.
    • Slopes – Stepping up the base course of retaining wall block or mortarless fence block is done with ease.  There is no need to bury more block than necessary, so you will not be buying additional block or concrete.
  • General Labor Force – Masonry experience is not necessary to build a landscape wall out of Allan Block modular concrete retaining wall blocks.  Utilizing your average do-it-yourselfer, or a contractor certified by our outstanding contractor certification program, a retaining wall can be constructed without the highly skilled know-how of a mason or concrete worker.

Whether your construction project is a small landscape wall in your front yard, or a 50-foot (15.25 m) retaining wall, a mortarless system is worth investigation.  These systems have stood the test of time, are flexible, cost effective, and with today’s technology can be the perfect solution for your project.