Building a Retaining Wall
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Building a Retaining Wall in Calgary is easier than you think. With advice from the landscape experts at Ornamental Stone, a retaining wall can be a great DIY project. In this article we will cover the basics when it comes to building a retaining wall or flower bed in Calgary.
First, we will go over some of the available options you can use to create a retaining wall. Then we will cover the required landscape equipment and materials needed to start your project. Once the basics are settled, we will get to the step-by-step guide you can follow to build a retaining wall.
Retaining Wall Options
The first step of building a retaining wall in Calgary is deciding what you want to build. There are a variety of options to choose from when it comes to retaining wall materials. Each provides a different aesthetic and has its own positives and negatives. There are three general categories of retaining walls to choose from:
- Natural Stone – Flagstone or ledgestone like our 1-3” Rundle Rock
- Concrete – Precast concrete blocks that are ready for an easy build
- Wood – Pressure treated or Cedar lumber
Our top choices are natural stone like ledgestone and precast concrete. Natural stone will never warp or fade and can be utilized to create a modern or rustic look. Ledgestone and flagstone can be used to create a dry stack retaining wall, great for flower beds or small accent walls around 1’ in height. Ledgestone can be used to build larger retaining walls, but will require mortar and proper backfilling, beyond the scope of today’s article.
Precast concrete retaining walls will last decades and provides a wide variety of sizes, styles, and colours. Stackstone is easy to work with and great for flower beds and smaller retaining walls. If you need to build a larger retaining wall or retain a large volume of material such as soil or gravel, Pisa2 is a popular option. Just remember, the City of Calgary bylaws require a permit for any retaining wall over 2’ in height. Building these larger retaining walls could also require changes to your grading and a certificate from an engineer.
Wood, even when pressure treated is prone to warping and fading and we would advise against its use as a long-term option. If you are drawn to the style wood provides, we carry the Bridgewood Retaining Wall from Barkman Concrete. The Bridgewood Retaining Wall has a realistic wood texture and will never rot, warp or fade like traditional wood. This is a great alternative for planter boxes.
Tools & Equipment
- Landscape Gloves & Safety Glasses
- Garden Trowel, Rake & Shovel
- Rubber Mallet & Chisel
- Wooden Stakes & String
- Hand Tamper
- Concrete Saw with diamond blade
Once you have gathered all the tools and equipment and chosen a retaining wall system, it is time to purchase landscape supplies. First you will need to measure:
- Mark where the front of the retaining wall will be using stakes and string and measure. If you plan involves irregular shapes or a flower bed, we recommend using a garden hose to create the outline and measure the length used.
- Determine the height of your retaining wall. Remember that in Calgary the retaining wall needs to be under 2 feet, or else a permit is required.
- Reference the spec sheet of your chosen retaining wall system (available on each product page in our online store). These guides will help easily determine the amount and type of blocks needed.
- Based on the linear feet and depth, calculate the required sand and gravel. For retaining walls up to 2 feet high, we recommend 6 inches of gravel and 1 inch of bedding sand.
If you need help figuring how much material is needed, check out our volume calculator for bulk materials. To calculate retaining walls, visit Ornamental Stone or give us a call at (403)275-5550.
Here are the landscape supplies needed to complete your retaining wall:
- Retaining Wall Blocks
- Crushed Gravel (Road Crush)
- 5MM Bedding Sand
- Landscape Fabric
- Construction Adhesive
Landscaping supplies can be found in Calgary at Ornamental Stone!
Building Your Retaining Wall
Now it’s time to build your retaining wall. You should have the spec sheet of your chosen retaining wall handy. This guide will assume installation of the Stackstone Retaining Wall from Barkman Concrete, which is an easy to use system for first timers. If you plan to use a different retaining wall block such as Pisa2 or Quarry Stone, the basic principles will still apply. We are always happy to offer advice and have additional spec sheets from the manufacturer.
Preparation is the most important part when it comes to building a retaining wall that will last long-term, so don’t skip over the first few steps. Before starting, please reference the Stackstone Retaining Wall Spec Sheet for information on creating curves and corners.
- Excavate – Dig out a trench 9” deep and 16” wide and shape the back slope to allow for 6” of drainage materials behind the retaining wall. Ensure the base soil is compacted.
- Prepare Base – Set landscape fabric down covering the bottom and up the back slope of the trench, make sure to leave some extra. The landscape fabric will prevent soil from seeping into the retaining wall and drainage rock.
- Create Base – Fill trench with Crushed Gravel and compact with hand tamper. Once gravel is tamped add the 1” of 5MM Bedding Sand for levelling the first course of blocks. You should end up with a base that is 2” below grade at the front.
- First Row – Use a level string line to mark your first row. Place the first row according to the spec sheet and ensure each block is level front and back. Your first row will sit 2” below grade for added support.
- Stacking – Brush the first row clean. Place the first block in the middle of the two lower blocks, so the center of the block aligns with the joint between the first two blocks. Staggering each course is needed for added stability. For interlocking each row, Stackstone uses a tongue and groove method; please refer to the spec sheet for more info. Repeat as needed to required height, leaving room for one more row of coping. Remember to stagger the first block of each row.
- Cut – You will need to cut a block in half for every second row, so that they align at the edge. If you are doing curves or other irregular shapes, more cuts will be required.
- Gravel Backfill – Fill behind the wall with Drain Rock, compacting every 4” until you reach grade. The drainage rock should be directly touching the retaining wall, with the landscape fabric separating it from the soil. Stop once you reach the last row of stacked blocks.
- Coping – For the last row of blocks you will use coping blocks that are smooth on the top. Apply two lines of adhesive, one on each side of the tongue of the row below. Place coping block on top and use pressure to secure.
- Soil Backfill – Pull the landscape fabric over the drain rock back towards the retaining wall. Use topsoil to backfill the remaining space behind the retaining wall.
- Grading – Ensure that your topsoil is sloped both above and behind your finished retaining wall. This ensures proper grading so water will flow away from the retaining wall.
Overall this project should take you and a couple friends the weekend to complete. Ensure you have all equipment and landscape supplies before starting. We recommend reading through this guide a few times before following it step by step. Feel free to visit Ornamental Stone at our location in Calgary and we can help you plan and build your retaining wall.