Can I Build a Fence on Top of a Wall?

If you want a fence on top of a wall, there are some things to consider. Is the wall already built? If it is, then you have to know how the wall was built; did they use geogrid, or is it a gravity wall? If the wall is in the planning stages, you have to decide the placement of the fence and how it will affect the construction of the wall.

There are many ways to build a fence above a wall. One is to have the fence set 3 feet (.9 meters) behind the back of it. This method is preferred because it does not require extra engineering. This requires construction tubes to be placed during the construction of the wall. If the fence is added after the wall is already built, the fence installer could damage the structural integrity of the wall. If the wall was built using geogrid, they could tear it, which will cause the wall to fail. Instead, they will have to dig the post holes by hand. If the wall is constructed using no-fines concrete, the fence installer will not be able to install a fence after the wall is built.  

A second method is to have the fence directly behind the wall. This requires a fence above the wall overturning calculation to be completed to understand how the fence interacts with the wall. This calculation determines the fence’s parameters; how deep do the posts need to be placed? How far apart are the posts? How tall is the fence? These factors impact the wall, which may cause the top to overturn and fail. To have the fence directly behind the wall, you will have to install the construction tubes during the construction just like the first procedure mentioned. A way to do this is with Sleeve-It. Sleeve- it is a product that is installed during the wall construction, but it does not require extra engineering for overturning. If you have any questions regarding this topic feel free to contact us at 800-899-5309, or email us at engineering@allanblock.com.

What is a Gravity Wall?

A gravity wall is a stacked block retaining wall that can stand up by the weight of the stone alone.

Gravity walls are usually shorter in height and consist of block and stone without the use of additional reinforcement.

To determine if your retaining wall can be a gravity wall, check out our Gravity Wall Chart. The chart will let you know how high your wall can reach to still be a gravity wall based on your project parameters.

What are my Choices in Color and Style of an Allan Block Retaining Wall?

Since Allan Block has been in business from the beginning of the modular block industry, there are many options available for you to match the look you want on your project. If you’re seeking an antique appeal such as “Old English”, then AB Europa might be the collection to choose. Maybe you want the split-face block and marbled color that is provided with the AB Collection. If those aren’t suiting what you’re looking for, the natural stone appearance of AB Fieldstone heightens aesthetics and differs greatly from the split-faced façade. Brand new to the AB family is the Aztec Collection, which has a smooth, yet textured face to give the wall many dimensions. The best part about using Allan Block products isn’t just that they have a style just for you, but you can find a color available that will accent your backyard to make your outdoor living space the talk of the town! For exact colors and availability, contact your local AB Dealer in your area!

What Does an Allan Block Retaining Wall Cost, and How Does it Compare with Other Types of Materials?

In comparison to other types of retaining wall material, Allan Block is very competitively priced.

To touch upon a few common choices, let’s first look at Timber. This type of system works, and has been tried and true over the last 50+ years. The problem is, they degrade in time. Although you’d have a low front end cost, the maintenance will cost you more through the years than an Allan Block retaining wall. This also doesn’t include the possible environmental disposal costs that can be associated with timber retaining walls.

Next, let’s discuss a natural stone-type retaining wall. These can be comprised of limestone, boulders, or other natural rock available in your region. Typically, natural stone is one of the most expensive options, as it isn’t always readily available. It doesn’t install as easily, and may require special equipment due to the size and weight of the material. Allan Block is a cost-effective solution with so many collections and finishes that look like natural stone in modular block, offering a cost advantage.

Lastly, is a traditional, cast-in-place masonry wall. These systems have full reinforced footings with rebar and require formwork typically to complete installation. These walls are expensive, and can drive up the labor cost due to the amount of embedment in northern climates. A ball park cost savings from a cast-in-place retaining wall to an Allan Block system can be roughly 50%. Allan Block provides an avenue to save money and have a wall that looks better.

Now that we know Allan Block is a cost-effective solution for nearly all sites, it really comes down to what collection and color you would like in your backyard. Visit allanblock.com to select a store near you, or call your local dealer for cost and availability.

Stairs Without Being Part of a Retaining Wall

I have a friend that asked me about building a new set of stairs from his cabin’s back patio area down to the lake.  His 20-year-old railroad tie steps were basically gone from deterioration.  The grade is not that steep, which makes his treads quit long relative to the 8 inch (20 cm) riser.  He said he was thinking about using wood again, because he did not think Allan Block products could be used for non-retaining wall applications.

Boy, am I sure glade he asked, because he was totally wrong.  The only limitation Allan Block walls have, is based on the creativity of the installer.  If an installer can think it up, then they can build it with Allan Block, and standalone stairs are downright easy.  In my friend’s case, the installer is simply building a series of one-course walls with cap units, over and over again rising up the grade.  He chose to simply fill in behind the caps with a nice crushed rock. 

Another option could have been to pour concrete or lay pavers for a more solid surface, like this similar project.

For more information on stairs using Allan Block, or any other questions related to Allan Block wall design or construction, contact Allan Block at engineering@allanblock.com.