Large Retaining Wall
For larger retaining wall projects, an Allan Block retaining wall is recommended.
Allan blocks come in a variety of shapes and sizes – but all of them are suitable for higher retaining walls that can support a lot of weight. These are big, strong blocks. Allan blocks are much larger than the Windsor blocks that I’ve mentioned in previous blg posts.
In the image below, you can see that this Denver customer needed a retaining wall to support their raised front yard. You’ll also notice that there is a cap on top of the retaining wall to create a smooth flat surface.
Most smaller retaining walls don’t require mortar or glue to keep the blocks in place. With large Allan block walls, good mortar / glue is a must. We use super strong glue which is designed specifically to keep masonry in place. We actually apply the adhesive through large tubes via a glue gun.
Use a French Drain with Retaining Walls
For larger retaining walls, it is always highly recommended to install a french drain behind the retaining wall. This holds true especially if the land is significantly sloped.
The french drain usually sits a few feet behind the wall and has gravel at the surface. The water drains through the gravel down into the drain and is channeled away from the wall.
The retaining wall is obviously supporting a lot of weight from soil and keeping everything in place. A significant risk factor for retaining walls is water pressure.
The french drain is able to whisk much of the water away from the wall and prevent failure of the wall. Without a french drain, water can work its way towards the wall, resulting in intense water pressure. This intense water pressure can cause a catastrophic failure of the retaining wall.
Retaining Wall Durability
When properly constructed, and especially with the assistance of a french drain, a retaining wall like this can last 30-40 years. Shifting soil and weather conditions can obviously affect the lifetime of a retaining wall, but they’re a great investment in your property. They create more usable space and help to prevent erosion.