Allan Block strongly recommends designing segmental retaining walls (SRW’s) using curves rather than corners. However, there are options to incorporate both inside and outside corners using Allan Block.

Each type of corner has their own unique modifications of block so let’s take a look at how you can install inside and outside corners when the need arises.

Inside Corners

Inside Corners can be easily constructed using any of the Allan Block Collections of products. Simply remove part of the lip on top of the block using a chisel or saw where the blocks intersect each course. For more details about constructing inside corners, check out our literature on building inside corners.

Outside Corners

Using the AB Corner Block, Outside Corners can be easily built. AB Corner Blocks are manufactured at a 12° setback but can be adjusted to work with any setback. Always start your wall at the corner and build out. For more information about adjusting the setback of an AB Corner Block, see AB Tech Sheet #298.

Miter cutting block is another option for when 90° corners or curves can’t be used. AB Tech Sheet #296 gives details on how to cut block to create 90° mitred corners. For corners that are greater than or less than 90°, simply divide the final corner degrees by 2 and cut 2 blocks to that degree before placing together.

For walls with corners that require geogrid, check out Corners with Reinforcement for details. If you have any questions about how to construct corners, reach out to us at engineering@allanblock.com.

How is Allan Block different? Although each set of stairs is unique, the same principles for installation and construction used for retaining walls can be applied when building stairs with Allan Block. We have technical data sheets covering a few standard designs and you can find these on our website.

Parallel with Round Curves

Perpendicular with Corners

Perpendicular in the Wall

What about treads and risers? Check with IBC and OSHA codes to verify the requirements but the full and half high Allan Block units can be used for the risers. The AB Capstones can be used for stair treads but don’t let that limit you, pavers, poured concrete or other natural stone products are a viable tread option as well.

Can you integrate stairs into the retaining wall? Integrating the steps directly into the wall itself is a possibility where the blocks of the wall create your steps as you build taller. Be aware of compliance to IBC 1011.5.2 and OSHA requirements detailing the riser height limits, as Allan Blocks are nominally 8 in. (200 mm) tall. This may necessitate building the steps of the stairway after the retaining wall sections are built. Separating the steps from the retaining wall gives you more flexibility to add landings to break up the stair line.

Next time you get a request to add stairs to a project know that Allan Block has you covered with creative ideas and construction support. Please reach out to engineering@allanblock.com or at 800-899-5309 x3 if you have questions or need design and construction assistance.