Hardscape Construction: Interlock and Retaining Wall Hardscape Installation

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Hardscape construction involves any building and installing of concrete products. In this case we are going to be covering the installation of pavers or interlock stones and the building of retaining walls.

There is a lot that factors that need to be considered when planning and installing your hardscape project. It is important to know every aspect of a project in order to properly install hardscaping materials. Otherwise all of your effort will be in vain and it will quickly be destroyed from traffic or freeze-thaw cycles causing more problems.

This guide will provide you with (almost) everything you need to know regarding your hardscape project. Things that are not included are regional-specific guidelines like the depth you need to dig for your project and the specific names of materials as they change from region-to-region. However, for the purpose of this guide we will be referring to Ontario, Canada as the location as it has some rigorous guidelines due to its many freeze-thaw cycles each year and because this is where we operate our business. These guidelines should be fairly similar to other regions that have similar freeze-thaw cycles in the northern United States and Canada.

Whether you are following this guide for a do-it-yourself project, you are wanting to start your own hardscaping business, or you want to add hardscaping to what your business already offers, you are in the right place. There is no other guide online that offers this amount of information all in one place.

This guide works best if you read it through once and make notes to understand everything that is required on your part, and then using it as an on-site reference should you need to be reminded of anything in particular.

If done right, hardscaping can increase the property value of a house and create an outdoor atmosphere that invites the envy of your peers. It can also become an extremely profitable part of your business.

Hardscape Construction:

Interlock and Retaining Wall Hardscape Installation

Table of Contents

1. Regional Permits and Guidelines

 

2. Required Hardscaping Tools and Equipment

 

3. Installing Interlock Walkways, Patios, and Driveways
• 3.1 Preparation: Design, Slopes, and Sub-Soil
• 3.2 Excavation and Base Preparation
• 3.3 Laying Pavers: Laying and Cutting
• 3.4 Polymeric Sand Installation: Sanding and Edge Restraint
4. Installing Retaining Walls
• 4.1 Preparation: Design, Slopes, and Sub-Soil
• 4.2 Excavation and Base Preparation
• 4.3 Laying the Base Course of Your Wall
• 4.4 Continuing Your Wall
5. Conclusion

1. Regional Permits and Guidelines

Though this guide serves as a everything you need to know about hardscape construction, it is really important to understand that regions have their own specific requirements for preparing your base. You need to check with your local regions for how deep you need to dig and the specific type of material to use for the preparing of that base as terms are used interchangeably.

For your reference, we are going to use the region specifications of Ontario, Canada. This is because this is where my hardscaping business is centered, but also because the area has many freeze-thaw cycles so this covers a lot of areas through the northern United States and into Canada that also experience many freeze-thaw cycles throughout the year.

We follow the ICPI guidelines. ICPI is the Interlocking Concrete Pavement Institute that is the governing body to set standards for the concrete industry. Be sure to check with these standards for your specific region, as well as your region’s guidelines on guidelines, permits, and locates. More on this later.

In Ontario, permits are not specifically required for the building of interlock patios, walkways, and retaining walls unless they measure more than one meter (3.2 feet) in height. In this case you will need engineered drawings in order to obtain your permit. Other specific instances in which you would require a permit would be if you needed to change the slope of a landscape.

If you are building a new driveway or extending an existing driveway, you will want to check with the municipality to know how large this surface can be. For example, in our region you are only allowed to make your driveways a certain width if it is not permeable so that it allows the ground to absorb the water instead of flooding the sewer system during a heavy rainfall. There are ways around this which would be to use a different material for your driveway extension than your driveway itself. That is why we see a lot of driveways that are asphalt with interlocking borders as the extension.

As always, double check this information specific to your region in order to continue your project.

2. Required Hardscaping Tools and Equipment

With any project you are going to need to have some equipment on-hand. Some of this equipment you will need to purchase if you do not already have and some you will be able to rent should you not want to spend the money on it.

Here we will list some tools and equipment that will be necessary for you with your installation that you may want to purchase or rent. We will also mark what step in the process they will be required for and whether or not it would be useful to rent rather than to own.

There are also some affiliate links included in this list. You can follow these to purchase your tools and equipment. We earn a commission at no extra cost to you and the commissions help us to keep this website running.

• Steel Toe Boots

 

• Safety Glasses

 

• Hearing Protection

 

• Dust Masks

 

• Work Gloves

 

• Tape Measure

 

• String Line – Slopes

 

• String Level – Slopes

 

• Shovel – Excavation

 

• Wheelbarrow

 

• Rake and / or Landscaping Rake – Base preparation and screeding

 

• Hand Tamper – Base preparation

 

• Level (4 Foot would be helpful) – Screeding

 

• Screed

 

• Steel Screed Bars Maximum 1″ Diameter – Screeding

 

• Push Broom – Polymeric sand

 

• Leaf Blower – Polymeric Sand

 

• Hammer – Edge Restraint

 

• Rubber Mallet – Retaining Walls

 

• Caulking Gun – Retaining Walls

 

• Chisel – Retaining Walls

 

• Torpedo Level – Retaining Walls

 

• Truck and Trailer – Excavation

If this is a one-time project, you may opt to rent this to dispose of what you excavate. You can alternatively hire someone to do the excavation for you, rent bins to fill with the excavated material, or use an alternative base material that we will discuss later in the guide.

• Mini Excavator or Skid-Steer

Another item you would likely opt to rent. These can be delivered straight to your site and picked up as well for convenience.

• Plate Compactor

You could rent this piece of equipment as well though if you are starting your own hardscaping business you would likely need this on an ongoing basis. If you are doing one job then these can be rented.

• Quick Cut with a Diamond Blade

Another piece of equipment you will likely want to invest in should you be starting your own hardscaping business. Rent fees on these can quickly add up and having one of these handy will keep you efficient. If you are doing one job then this can be rented.

3. Installing Interlock Walkways, Patios, and Driveways

3.1
Preparation

Design

First things first when deciding to install an interlock patio walkway or driveway and that is knowing what area you are going to cover. We are going to discuss measurements, material, and understanding the slope.

We need to think about the design beginning with the shape of your project. If you are going to go with a square patio, walkway, or patio, then it will be the easiest as far as cutting is concerned. If you want to have more rounded and sweeping edges, you will use more material and spend more time cutting.

Measuring your entire yard and plotting it on a piece of paper or using SketchUp to map your project in 3D will help your understanding of your design and what it will look like. If you are dealing with a customer, this will also provide a visual sense of what they are agreeing to have done to their property.

If you are installing a driveway, it is pretty simple when it comes to a design and the slope because you have a start point (the base of your garage) and an endpoint (the top of your sidewalk). The slope is already predetermined so you do not need to measure for this. If your driveway is rectangular, then the only design you likely have to plan for is the pattern of the interlock and the border stones. If your customer has a larger driveway and wants a more intricate design, you still will likely not need to worry about the slope as you still have a beginning and ending point.

When you are installing front walkways, side walkways, or an interlocking patio the design can get a little bit more complicated. Not only do you have to create the outline of your project, but you also need to figure out your slopes. You can also incorporate more features into patios such as barbecues, outdoor kitchens, fire pits, and so much more that you need to account for should you be planning your design. You need to really jot down your ideas and create a rough sketch of an excellent visual as to what you are going to do. A lot of this has to do with creating a budget for your project.

Hopefully you have that design in your head or you jotted it down and you ready to take measurements of your project. Those measurements are going to provide you with the amount of materials that you are going to need by measuring all four sides of your walkway, patio, or driveway to give yourself the dimensions needed to calculate the square footage.

If you do not remember the calculation for square footage, it is length times width (length x width). Therefore, if your project is square (the two lengths are the same and the two widths are the same) it is a simple length times width calculation to give you the square footage. Should you be needing to incorporate curves into your design, make these curves into squares for calculation purposes as you will likely be using the extra materials for cuts.

Now that you know how much your square footage is, you are going to need to order your product. You may want to wait for what other materials you will require such as base material, landscaping fabric, edge restraint, polymeric sand, and any other materials needed to get them delivered all at once.

When choosing the right product to install you will need to consider the type of traffic that will be moving on your finished product. If you are installing a walkway or patio, the traffic will be people and therefore not a major pressure will be exerted onto your pavers. In this case, you are looking for pavers that are generally 60 mm (2 3/8″) thick.

However, if you are installing a driveway then you will want your pavers to be thicker, generally 80 mm (3 1/8″) thick. This is because the force exerted on the pavers from vehicles will crack the thinner the paver is. There are some exceptions to this rule as pavers that have a small surface area like a 4″ x 8″ standard paver can be 60 mm (2 3/8″) thick because they have less of an area that the vehicle will drive on and therefore be less likely to crack under the force. You can also install natural stone for walkways and patios that is 1″ (inch) thick.

When I meet with a client to decide which type of product they want installed, I start them with these two options: textured or smooth. Whether they want a textured or smooth product, my next question is whether they want a small or medium sized stone. Smooth products are typically only supplied in medium and large sizes, and I try to stay away from installing large sized slabs as it can be very labor intensive. If the client chooses smooth, they are likely going for a modern look and I have just the right medium sized paver to offer in this scenario. If they want a more traditional look then I have a few options for them to choose from that have a textured surface in both small and medium sizes.

Being prepared with products that you know and enjoy installing is extremely important when meeting a client. You should have choices for all scenarios and be willing to offer solutions that fit their needs. Doing research on the types of products that are available to you and making sure that they are in stock or available for purchase in small quantities is important.

Slopes

You need to make sure you have a proper slope from the top of your walkway or patio to the bottom. Remember, we already discussed that driveways have a predetermined slop from the top of the garage floor to the sidewalk. Walkways and patios are a little more trickier in this regards.

Walkways and patios need to follow the slope of the existing land. If the slope is to steep, then a retaining wall may be required. This creates a raised patio effect and will be covered later in this guide due to its complexity.

If the slope of your landscape is gentle, then you should have no problem building on top of the existing land. A front walkway is likely going to follow the slope of the driveway as long as your driveway is not too steep. Again, if the slope is too steep you will need to build some steps to level out the ground in order to make a safe walk up to the front door especially in the winter time. More on this later in the guide due to its complexity.

Walkways and patios need to have a minimum slope of 1/8″ (inch) for ever 1′ (foot) and no more than 1/4″ (inch) for ever 1′ (foot) away from the direction of the house. This is to ensure that the water runs away from the foundation of the house to ensure to water gets into the footings of the house and into the basement, but also to make sure that the slope is not too steep so that you can sit or walk on the project without feeling like you are falling over.

In order to measure this slope we are going to use either a laser level or spikes with string line and a string level. I typically use the string line method as you do not require another person available to help with the laser level measuring and it provides me with a good visual of where the top of my pavers are going to lay.

What we do is hammer a spike in all four corners of our walkway or patio and wrap a string round the spike at our foundation at the level where we want the top of our paver to lay. We then take the other end of the string and wrap it around the spike on the same side furthest from the house and wrap it around. We then put the string level in the middle of the string, making sure the string is tight, and make sure it is level by adjusting the string line furthest from the house.

Now we use the 1/8″ every foot rule to adjust the string line furthest from the house. Since we know the slope measurement for every foot, we need to measure the length of the patio or walkway from the house to the end of the patio to provide us with how many feet long it will be. We multiply that by 1/8 to provide us with how many inches we move the string furthest from the house down.

For example, if the patio is going to be eight feet from the house, then we know that we need eight 1/8″ which is one full inch that we need to move the string line down. Now you know where your the top of your pavers are going to lay. If they are slightly too high compared to your existing landscape, but not high enough that you would need to build a retaining wall, then you could lower the string line a little bit more making sure you do not make the slope steeper than 1/4″ for every foot. Another option would be to add a step from your back door and start your pavers at the house lower in order to meet the landscape further from your house.

Sub-Soils

The next step is to understand your sub-soil. This involves digging down through the topsoil to understand where the sub-soil is and what kind of sub-soil you are dealing with.

In Ontario, we have a few different sub-soils including bedrock, clay, and sandy. Be sure to check in with your area to inquire what kind of sub-soils are present. Hitting something like bedrock can cause major problems with your project, while clay blocks the passage of water and is difficult to dig through causing your labor to skyrocket, and sandy soil is great for allowing water to penetrate through and for the ease of digging.

It is good practice before you begin your project to dig down a little to see what is there. We deal with a lot of clay in our area and need to excavate a proper base in order to deal with this, as well as being sure to use landscaping fabric to separate this material from our base material which is also a good practice in any scenario.

3.2
Excavation and Base Preparation

Excavation

Now that we have identified the shape, slope, and sub-soil that we are working with, we are almost ready to begin our excavation. Before excavation begins we need to order a locate to find out where our hydro, electric, phone lines, and any other structures that we might hit are. In Ontario, we have a service called Ontario 1 Call that provides a free locate.

They will come out and locate everything that is underneath where we will excavate. Though they do not provide the depth, they do tell us to hand dig within three feet of the markings to make sure nothing gets hit. This is an extremely important step before excavating and is law here that we need to follow before digging. Make sure you know who to call to order a locate before beginning your excavation.

If you happen to hit something when you are digging, be sure to call the homeowner who then needs to contact the governing body of what was hit whether it is the city or a phone company. It is extremely important to be honest about this and careful whenever digging around an underground structure.

When it comes to excavation, you have two options. You can either hand dig or use a machine to dig. Hand digging obviously involves more labor, but it is the cheapest option as far as equipment is concerned. Using machine will take less time and involve less labor, but is much more expensive.






If you were going to get a machine on site then you need to know if you have the accessibility to get to that particular spot where you are going to be excavating. You need to ask yourself if there is anything in the way of the route including having enough space between the houses, an air conditioning unit that is in the way, and a backyard gate being wide enough among other things. You also need to consider that you will have to replace the existing sod that is destroyed by the tracks of the machine or wheelbarrows that you use when hand digging if you choose not to protect it with plywood.

Once you have decided whether you are going to hand or machine dig, the next step is deciding what to do with the excavated material. This can be an extremely costly step and it is important to understand how much material you will be excavating and planning for how to dispose of that material.

In order to calculate how much material will be excavated in cubic yards, you need to follow this simple calculation: Length in feet times width in feet times the depth in inches (more on how deep you need to excavated shortly) times 0.003.

Length (Feet) x Width (Feet) x Depth (Inches) x 0.003 = Cubic Yards


Now that you know how much space this will be taking up once it is excavated (it takes up more space once it has been excavated because it has been compressed for many years), you should also know how much this is going to weigh. One yard of excavated topsoil will likely weigh at least 2,500 lbs or even more when it is wet.

Now that you know all of this information, you can decide whether you want to use your truck and trailer to dispose of this yourself based on how much your trailer can hold, if you want to rent bins to have this soil be disposed of, or if you want to hire somebody else to do this part of the work who is more efficient at excavating. If you choose to excavate this and dispose of the material yourself you will need to know where the closest landfill site is to dispose of it, factor in the costs of dumping there, as well as the fuel and time involved in doing this. If you know somebody at a farm that needs this material, even better to get rid of it there.

A minimum of 6″ – 8″ (inches) is required for the base of a patio or walkway, whereas for a driveway you want to prepare a base of 12″ – 14″ (inches) to allow for the support of vehicle traffic. Therefore when calculating the depth of how much you need to excavate, you need to add the depth of your base PLUS the depth of the paver that you are installing. Most pavers fall between two and three inches, so you are likely looking at anywhere from 8″ – 17″ (inches) depth between a walkway or patio to a driveway. You also want to excavate 6″ (inches) past where your pavers will lay in all directions.

There is an alternative to excavating and preparing a traditional base on the market at the moment. It is fairly new and requires only one inch of base material. This saves a majority of the digging, disposing, and installation of base material. We will talk about this product on a future post. We will continue covering the installation of a traditional base in this guide.

Base Preparation

Once you have excavated all the material and measure down from the string line that you created to be the top of your pavers, you are now ready to do you first compaction. Every step in hardscaping is extremely important to ensure a proper base, but this is one that often gets missed. You should use a plate compactor to vibrate the sub-soil to be compacted before continuing any further.

After this you can now install the woven geotextile landscaping fabric. It is important that you are using the woven product which looks and feels like plastic fibers woven together as opposed to a felt-like texture. This will help keep the water away from your foundation as the water will follow your slope and slowly bleed through the fabric into the sub-soil. It will also add strength to your base and separate it from your sub-soil so that there is no cross-contamination between the two materials. This fabric should be installed in a shingle pattern, overlapping parts should you not have a piece that fits the entire shape of your design.

For the base material you are going to use what is called Granular “A”. This is a three-quarter crushed stone that allows for the passage of water through your base, as well as a fine material mixed in to allow the material to bind together giving your base that cohesion and compaction.






This base gets compacted in two to three inch layers moving up towards one inch below the bottom of the pavers. That means you need to measure from your string line the depth of the pavers PLUS one inch. That is where you stop your Granular “A” base. This remaining one inch will be for our screeding layer where we level the area to lay pavers on top of.






On a side note, if you want to add more strength to your driveway, you can add bi-axial geogrid between the layers of Granular “A” as you compact it. This geogrid provides strength and stability to your driveway as it prevents any movement of the base material from freeze-thaw cycles and vehicular movement and weight. Basically it keeps the gravel in place as opposed to moving from any stress put on it.






Screeding

With our final inch, or less, we will be screeding this level. Screeding involves the placement of two bars and scraping back the gravel to provide a level surface. However, we first need to decide on the type of screeding material we want to use.

Traditionally what has been used was something called stone dust or lime screenings. This has long since been disregarded as something you should use as it does not allow for the passage of water. Water will sit right below your paving stones and pop them up between freeze-thaw cycles. Nowadays what is used is either concrete sand or high performance bedding.

Concrete sand has traditionally replaced stone dust as the screeding layer. However, the unfortunate part of using this material is that if you install more than one inch of it, it is more likely to cause the sinking of the paving stones due to its lack of compaction. Also, you cannot work in the rain with this material as it will just wash away.

High performance bedding or HPB on the other hand can be installed at one inch or more, though on driveways you still should not exceed one inch, and you can install it in the rain. This is because their are no fines within this material. It is 1/4″ (inch) crushed stone which provides a high rate of compaction. So much so that you do not even need to tamp it to compact it. Once it is laid, you already have higher than 95% compaction. Another plus to it is that it allows for complete passage of water as there is no fines to block any of the water from passing through. It really is the best material to be working with.

Now we want to set our screed bars in place. We are going to choose a corner against our foundation where we will start our screeding. We are going to place our screed bar on the compacted base and measure against our string line to make sure the screed bar sits where the bottom of the paving stone will lay. The screed bar should follow the slope of you string line.






As long as your walkway or patio is level against the foundation, you can then lay the next screed bar four or less feet (this depends on the size of level you have, you could increase this distance to save time with your installation if you have a larger level) from the first screed bar, make sure it is level, and then fill in the void with your screeding material.

With this void between the bars being filled, you are then going to scrape back the material using your level to create a smooth and level surface for where you pavers are going to lay on top of. You will repeat this step by taking the first screed bar, or if you have more then it will be even better, and placing it next to the second screed bar. Once you have the first portion of your project screeded you can begin laying or you can make sure the entire project is screeded.






It is important that you are filling in the voids left by the screed bars themselves as you lay, otherwise the indents will cause your pavers to collapse inwards.

3.3
Laying Pavers: Laying and Cutting

Laying

You want to make sure that you are laying your pavers square to the foundation and following a straight line. Hopefully you have already created that square with your string line. You can measure a square area by measuring the diagonals in your square to make sure they are equal in length or you hold up a large enough square tool to your line and the foundation to make sure you are square.

While you are laying, you will want to make sure that your line is not deviating from this straight string line, otherwise you will get some crooked lines in your project. Checking your line at various points is always a good idea.

You also want to know the pattern that you are choosing to lay. A lot of manufacturers offer their various patterns in their spec guides that are available online, or you can choose to lay the pavers in a random pattern of your choosing. This will make sure the project moves at a faster pace when you do not need to keep referring to a pattern or if you mess up the pattern and need to go back and fix it.

However, if you do choose to lay randomly, you will want to make sure that you break up any long lines in your laying pattern. These lines are created by the same edge of the pavers lining up over a length of three feet. If you have a straight line in your pavers (except in the borders or if you are laying your pavers all in a straight line) of three feet, you are going to want to break that line up with another paver whether you choose a smaller one, larger one, or turn one in another direction.

When laying a stone, you want to make sure you are not disturbing the perfectly screeded base below it. You will want to click the stone you are about to lay against the stones that are already laid and slowly bring it to the base while pressing it against the edge of a neighboring stone. This will ensure you do not disturb your base. Also, do not walk on yours or anybody else’s perfectly screeded base, that is a big no-no.






Cutting

If you have a square area that you are paving, adding a border to it is simple and will have to be laid as you are laying the interior stone. That means that the first stone you lay should be your border and you should continue by laying your border stones and interior stones as you commence through your project.

The good this about this is that there is minimal cutting required. You may need to cut half stones to fit on either side or with the right stone sizing and random pattern, you could be able to get away without cutting any stones. However, designs including curves you will be less lucky.

Cutting involves using a diamond blade on a quick cut saw. The quick cut saw will allow you to cut those curves properly.

What we do when we are planning our cuts is we lay our stones past the area where the cut will eventually be. This involves using more stones to lay the interior stones where the border stones will actually be laying. At this point, I can then lay my border stones ON TOP of the interior stones that I just laid in the correct shape that I want the border to follow. I can then run a chalk line or marker against these stones for my cut line, push the border stones away, and follow that line with my saw without having to painfully removing each stone at a time to cut it.






When cutting a curve, you will want to ever so slightly angle your blade away from where the border stone will be. This will allow you to follow a gradual curve in your cutting and it will also allow you to make sure that your border stone will sit nice and snug against your cut.






When you are cutting you should be using a dust mask to protect your lungs, steel toe boots, ear protection, and safety glasses. In some regions, there are dust laws in effect which prevent you from creating dust from your cutting. There will be dust and lots of it when you do your cuts. If you need to manage that dust, you can connect your quick cut directly to a hose and turn the water on. This will keep the dust down, but create what is called slurry.

If slurry is left on your stones and it dries, it will stain your stones with a white haze. You want to make sure that you are washing this slurry off regularly when you are cutting to prevent this staining. If it does harden, you can get down on your hands and knees to scrub it off or you can use a chemical cleaner to remove it.

Cutting can really make or break your installation, so make sure you have some practice with the quick cut saw before you get started. Safety is the number one priority.

3.4
Polymeric Sand Installation: Sanding and Edge Restraint

Sanding and Edge Restraint

Now that your cuts are in place, you are ready for the final stages of your installation. Edge restraint keeps your pavers from moving laterally. It is shockingly expensive, but necessary. It is simply a plastic edging material with metal spikes that get hammered in every foot. If it is covering a curve, you will want to add some more in to help contain that curve.

You want to make sure your spikes WILL rust. You want them to rust because they will grip the ground and your edge restraint better preventing them from popping up during freeze-thaw cycles.

Some people I know mix concrete to create a small three inch taper from the ground to the mid-way height of the pavers to act as an edge restraint. It is a cheaper option that may require slightly more labor.





Sanding creates a tight bind between stones and allows them to act as one unit. I recommend nothing but polymeric sand for this application. Polymeric sand is the mixture of polymers and sand (sometimes some cement dust) that creates a flexible yet hard compound between your stones. This compound prevents weeds, insects, and wash out of your sand over time. The alternative is jointing sand which has no properties to prevent weeds and insects and it will eventually wash away.

To install the polymeric sand, you need to follow the directions provided on the bag specific to the sand you have purchased. Generally this process includes:

1. Sweep any dirt or debris off of the surface of your stones.

 

2. Pour your sand on top of your stones making sure not to pour one bag out in one spot, but to slowly pour it over a larger area.




 
3. Sweep the sand into the joints of the stones and repeating the previous step until you have filled in all of the joints. You do not want to sweep the sand more than ten feet in any direction. Doing so would separate the polymers from the sand particles.




 
4. Compact the sand into the joints using a plate compacter. You will want to protect your pavers by adding a mat or some sort of scratch-proof guard between the metal plate and your pavers.




 
5. After compaction, the sand should have fallen in place by a third of the height of the paver. Your pavers should not be moving and everything should be locked in place. You can now fill in the remaining sand, keeping the sand level 1/8″ (inch) below chamfer of the stone. Any more and the sand will wash onto the stones and solidify on top. Being below the stone also creates a channel for water to flow.

 

6. Use a leaf blower to blow off any excess sand and especially the cement dust should your polymeric sand include that.

 

7. Set your hose to a shower and water the sand as directed on the bag. Generally you want to shower the stones and not the joints, making sure that once you see the white foam appear you are moving onto a new section. You absolutely should be starting from the bottom of your slope and moving your way to the top. This ensures that you are not accidentally activating any of the polymers.

Once your polymeric sand is installed, you are ready to clean up your project by repairing any sod that needs to be repaired, filling in the sides of your excavated project with new soil and seeds, and cleaning up your tools.





 

4. Installing Retaining Walls

Retaining walls involve different steps than installing a walkway, patio, or driveway, but require similar tools and some similar techniques involving the preparation and excavation of your project.

If done properly, your retaining wall will stand straight for many years to come and it will be a very great portfolio piece that you can show clients.

However, when skipping a step the wall is likely to fail over freeze-thaw cycles and traffic. Just walking around your region I am sure you will find many different examples of failing retaining walls.

Remember to research certain permits in your region that you are required to obtain when building a retaining wall or changing the existing landscape in any way. For example, in my region you are required to obtain a permit for walls higher than one meter (3.2 feet).

For more information on permits and guidelines we will be following in this guide and why, refer to Regional Permits and Guidelines earlier in this guide. In addition to permits, you will want to order locates for where you will be excavating to make sure there are no underground structures that you will hit when digging.

For a list of tools required for this work, refer to Required Hardscaping Tools and Equipment earlier in this guide, making note of the additional tools you would need for retaining walls.

4.1 Preparation: Design, Slopes, and Sub-Soil

When it comes to designing your retaining wall, you want to choose a stone that matches your budget and the height that you will want to build your wall to. A typical wall product has a minimum depth of 8″ (inches). This is to ensure the stability of the wall with the extra weight and depth to keep the soil behind the wall retained. Anything less than that may not be enough to retain your soil and you may be dealing with a leaning wall in the future.

You want to choose a starting point and an ending point to your wall. If you are building a wall down the side of your driveway, you may want to consider a return to your foundation. A return is a corner in the wall instead of just creating a straight wall that allows soil to flow off of the end of the wall.

Once you have a starting point and ending point to your wall, you can decide the height of the wall and begin to choose the type of stone you can use for your wall based on this and how high the wall product was engineered to be built. Again, some wall products were engineered to only be built to a certain height. If you are building a high wall you may be looking at using a wall block that is much heavier and requires a machine to install. If your wall is lower than one meter (3.2 feet) you likely have many options to choose from.

When it comes to slopes, retaining walls do not work the same as walkways, patios, and driveways that need a slope. Retaining walls should have no slope. They should be completely level. A slope in any direction will cause that wall to lean in that direction and collapse over time.

Preparing a wall on a sloping landscape involves having to step down your wall to ensure that you wall does not continue above your landscape. Your wall should always have at least one course or a minimum of 6″ (inches) buried, but more on this later.

Refer to identifying your sub-soil as it is the same as it would be if you were preparing a walkway, patio, or driveway.

Much like you would create a string line for a walkway, patio, or driveway, you will do the same for your retaining wall. In this case the string line is going to be level and it will show where the top of your first course or your buried row will land and it will help you by keeping your wall nice and straight.

We will cover the process of setting up this string line once the base has been prepared.

4.2 Excavation and Base Preparation

Earlier in this guide we discussed excavation and base preparation. It may be useful to go back and review this as a lot of that information is relevant to this section including: ordering locates, hand or machine digging, safety, excavating and disposing of material, bringing in material, and how much material you will be excavating and bringing in.

The way a retaining wall differs from that of a walkway, patio, or driveway in terms of excavation is the area and depth that you will be excavating.

For your retaining wall, you will be excavating a depth of 6″ – 8″ (inches) for the base material PLUS the minimum 6″ of the buried course of your stone. This makes the depth that you will be digging approximately 12″ to 14″ (inches). You will also be digging the width of your stone (we discussed earlier that walls have a minimum of 8″ depths) PLUS 6″ (inches) in the front of your wall and 12″ (inches) at the back of your wall. This is to allow for a proper drainage material to be used as fill.

PLEASE NOTE: The manufacturer of the stone that you are installing will have guides as to what else will need to be added. This example is for a small retaining wall. The higher your retaining wall, the more complex that these systems become. The manufacturer has engineered drawings that are supplied to you where you can choose the height of the wall and see how far back past the wall you will need to fill with setbacks, drainage material, and geogrid. We will cover these more complex walls in future posts, but for now we will not be covering walls installed with geogrid reinforcement in great detail.

You are now ready to use your plate compactor to tamp the native soil to make sure it is compacted. Then you are going to line the trench with geotextile landscaping fabric that will cover the entire trench and then on top of your backfill drainage material. To break this down for you, the length of the piece should be a minimum of: 6″ (to cover the face of the buried stone) + 24″ (to cover the bottom of your trench) + the height of your wall + 12″ (to cover the top of your backfill drainage material and to be tucked underneath the top layer of your wall).






You can now start to install your Granular A base material (3/4″ crushed stone mixed with fines) in 2″ to 3″ lifts on top of your fabric and compacting as you get to your desired height. To know the desired height of your base you are going to want to set up that string line from the start of your wall to the end, measuring it to be the top of your first course of the wall, and making sure it is level. This will be the line that will keep your wall straight. You can leave 1″ (inch) for your screeding layer to level your stones.

With the compacted base material installed, you can now screed your final layer using your screed bars and leveling material as discussed in the screeding section of the guide above. You will not want to screed the entire length of the wall especially if you have some step downs to account for. More on step downs in the next section.






Your base is now prepared for your first course of your wall.

4.3 Laying the Base Course of Your Wall

You will want to start at the top part of your wall where the slope is the highest and work your way down. The first course is always the most difficult part of building a retaining wall, so have patience during this portion of the wall and everything else is smooth sailing.

Place your first piece of the wall on your screeded bed, following your string line, and place your torpedo level on top of it. Use your mallet to make sure your wall is at the height of your string line and level in all directions. Making sure it is level is crucial to the longevity of your wall. Once level, you can continue to the next stone, placing it without sliding it on your screeded layer, and making sure there are no voids in the front face of your wall that will be noticeable.

Continue with your wall, stopping every few stones to place a longer level across the stones to make sure they are level with one another and taking a step back to see how the stones are following a straight line.

If your wall follows a slope, you will need to plan for step downs. At any point your wall becomes only 4″ (inches) buried because of the slope of your existing landscape, you are going to want to step down a full stone. You will have to choose the points where you will need to step down while laying your first course.

Once you are at a step down, you will want to take off your previously laid stone, dig down the depth of your wall stone at the halfway point of that leveled stone, and continue screeding from that new level of your wall. Once you have placed and leveled that first wall piece of the step down, you can now place the wall piece that you originally took out to place half on the existing leveled material and half on the step down wall piece.

4.4 Continuing Your Wall

Your first course is complete, you may have had to do one cut at the end of you wall to make it all fit. Now you can install a perforated drain in the back of your wall to allow for any water that was collected and filtered through from the top of your wall to the bottom to be collected. The perforated drain goes behind your base course of your wall.

You can now continue laying the remaining layers, one layer at a time. Remember that a wall only works properly when you stagger the joints. This means that there should be no vertical lines in your wall joints. This will add strength to your wall and keep it from falling forward from the force of the material behind it. Staggering the joints may mean you will need to cut the first stone you place on your wall for the next layer.






When placing the wall pieces you want to sweep the wall that you are placing it on top of to ensure there is nothing that will cause the piece to not sit flush. You will not need to glue each layer, only the top layer. Once you have laid the second layer, you can now fill in with 3/4″ (inch) crushed stone in behind the wall on top of the fabric and perforated drain. You only want to fill to the bottom of the last row you have laid.

Continue laying the remaining layers until you get to the final coping layer that will be the top cap of your wall. At this point you will want to compact your 3/4″ (inch) crushed stone to ensure complete compaction. You can then take your fabric and lay it on top of your crushed stone and lay it partially on top of your second to last layer before laying the coping layer on top.






If you have a step down, you are likely going to have some pieces of your top layer with a smooth side exposed at some point. You can make this smooth side into a rock face using a chisel and hammer. Simply create a score around the block with your chisel 1″ (inch) or more from the edge. If you start your score less than 1″ (inch) from the edge then you are likely not going to get a proper rock face when it splits. Slowly flip your block around and around continuing the score around the entirety of the block. Continue doing so as you slowly increase the force of the chisel. Eventually this piece will fall off leaving you with a rock face.

Once your coping layer is in place you can glue each piece down using proper polyurethane adhesive that allows for flexibility without cracking. With everything secure the last stage is to fill in the final height of the coping stone with top soil on top of the fabric and seeding or installing sod along that back 12″ (inches) stretch, as well as at the front of your wall for the first 6″ (inches) unless that will be paved.

5. Conclusion

You now know just about everything you need to know about hardscaping. Everything else can be built applying these concepts including raised patios and steps. We will be posting more on these subjects on a later date as they are more specialized builds.

Other things that we will be posting about will include topics like:

• Raised Patios
• Steps
• Gravity Walls
• Geogrid and Setbacks in Walls
• Overlays
• New Hardscaping Products and Installation Materials
• New Hardscaping Techniques
• Drainage
• Starting a Business
• Getting Clients
• Selling a Job
• Site Effeciency
• Creating a Contract
• And So Much More

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