Planning your Allan Block Project
Careful planning is the key to a successful wall project. Follow these simple guidelines to ensure the walls you build will stand the test of time. Use the information here and then the guide for landscape walls to plan, design, and build your own landscape project.
Start by determining the overall purpose of your project. Are you trying to create more usable space, solve a drainage problem, or simply add curve appeal? Do you want planters, stairs, or other design features?
Once you have your wish list, you can determine if where and how you will build it. Sketch out the position of the walls on a scale diagram taking the necessary measurements as needed. Indicate the position of all structures, trees, and landscape features. This plan is you initial blueprint for the wall. Check your local building code. An approved wall design may be needed to get a building permit for walls above a certain height. Call the local utility companies before you dig to have them mark the location of the utility line. Buried lines are not only dangerous but may also prevent you from building the wall where you want. It’s also a good idea to verify the lot lines and inform the neighbors that there will be construction going on.
When planning your project, make sure you can access the site with construction equipment and materials. For sites with restricted access, plan out where you will stage and store your block, wall rock, and other materials. In this example, access is extremely limited. And materials will need to be carried on to the site. If building on a hill or a slope, the placement of your wall would determine how much soil will need to be removed or brought on to the site.
A cut site is where you cut into the hill site to remove the soil from infront and behind the wall location. You will need to decide ahead of time what will be done with the excess soil. A fill site is where you will need to fill in behind the entire wall with backfill materials that will be brought in. You will need to plan ahead to have these materials brought on to the site.
Before beginning construction, determine the type of soil you will be building on. Granular and sandy soils are much better to build on as they allow for good drainage. Clay soils will stick together and put pressure on the walls. Organic soils will also stick together and hold moisture and should only be used to finish off the top eight inches of the wall.
Refer to the soil reinforcement charts in the landscape walls guide to determine how to build the walls specific to your site and soil conditions. 90% of wall failures are caused by poor water management. Once you have determined the water on your site, you must manage the water in two ways, surface run off and in-wall drainage. Surface run off from rainfall and concentrated water sources must be directed away from the wall. This can be done by grating the site and incorporating berms, drainage ditches, or swales to prevent the water from being collected above the wall. Identify concentrated water sources such as slopes above the wall, driveways and slopes toward the wall, roof down spouts, sprinkler and irrigation systems and outdoor faucets.
When designing walls that will be exposed to these concentrated water sources, build in swales and berms to route the water away from the wall. Oftentimes, you can hide the swales and berms with plants and landscape materials. In-wall drainage is meant for incidental water only and is managed through the use of wall rock and toe drains. Use wall rock in the block course and 12 inches behind the wall to ensure in-wall drainage. Toe drains are used to prevent the water from being trapped behind the wall and building up pressure. They must be positioned directly behind the wall at the lowest point possible allowing the water to be vented to daylight. If you encountered ground water on you site, contact an engineering professional for assistance.
For the next step in Plan Design Build, go to the Designing your Project section or visit us at allanblock.com.