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Each Wall Is UniqueEach wall is different, and the specifications for each wall can change. For example, if you need a 1' garden wall it isn't going to require much if any gravel backfill. But if you need a 12' wall that's supporting a pool, 2-3' of backfill (not the standard 1') would be necessary.
If your wall is 4' or higher, or sometimes even shorter depending on the circumstances, geogrid is required to provide lateral reinforcement to your wall. If your wall is located in an area that has an extraordinary amount of water flow it may need additional drainage built into the wall to allow it to drain more quickly. At the end of the day, each wall is unique and needs to be treated as such. And if in doubt, playing it safe and over engineering a retaining wall ensures that it is built to last. Different Types of Walls
6"x6" Timber Walls
These walls are built with 6"x6" pressure treated lumber. Each course is nailed together with metal spikes, and "deadman" (6"x6" timbers attached together in the shape of a T) are used behind the wall to give it lateral strength. The pro of timber is normally price and speed of installation. However, in 2021 it's not much cheaper than a concrete block wall because of a surge in the cost of lumber (covid + market demand for lumber). The downside of timber walls is that wood is an organic material, and it will eventually rot and need to be replaced. Concrete Block Walls These are the most popular walls, because they are cost effective, beautiful, and last a lifetime when properly installed. Concrete block walls don't require lateral reinforcement unless they are built 4' high (some 3' walls need lateral reinforcement). For walls that do require lateral reinforcement, geogrid is required to keep it from falling forward. Click here to read about geogrid. Natural Stone Walls Natural stone walls are generally the most attractive. They look natural and are considered high-end. Also, they can last a lifetime, just like concrete block walls. However, they are 25-100% more expensive depending on the specifications. Often, clients will opt for this type of wall in small areas or as part of an outdoor living space (sitting walls, outdoor kitchens, etc.). Most opt for a concrete block wall for large or highly structural walls. Stone walls can be built purely with stone, like boulder walls and stacked stone, or they can be built as a veneer. A veneer wall is when the wall itself is built out of cinder-block, and then it is faced with natural stone. |
The Process of Building a Wall
Planning
Where should the wall begin and end? Where will the drain from behind the wall? Do we need a permit? How tall should the wall be? These are just some of the questions that need to be answered before a shovel should ever break ground on a wall project. Check out our design and build page for details on design.
Digging the Trench
The first row of wall block needs to be at least partially underground. This means that a trench must be dug to allow room for the footer (6" compacted gravel) and for a few inches of wall to be buried. The trench should be dug approximately twice as wide as the blocks, and all loose or soft soil must be removed. It's crucial that the exact location of the wall is determined before digging the trench, as it will outline the path of the wall.
Building the Footer
#57 Stone or Crush n' Run is brought in and poured into the trench. It is then raked smooth and roughly leveled. We use a combination of running a plate compactor and hand tamps to compact the base to 100% compaction. For Crush n' Run this must be done in 3" lifts. We continue to add and compact material until we have reached our 6" minimum footer (6" is standard, very small walls may require less, and large walls can require more).
Leveling the First Course of Blocks
This is crucial. If the first course of blocks is not level, the wall will get more and more unlevel with each level of block that is stacked. We used small torpedo levels and 4' levels to check that each block is level itself, and that it is level with the block it's next to. If the footer is #57 stone we often level the base blocks in a bed of mortar. This adds strength and makes it easier to get each block perfectly level. If the footer is crush n' run, a small bed of masonry sand (1" or less) is added to allow for easier block leveling.
At this point, the wall should look something like this:
Where should the wall begin and end? Where will the drain from behind the wall? Do we need a permit? How tall should the wall be? These are just some of the questions that need to be answered before a shovel should ever break ground on a wall project. Check out our design and build page for details on design.
Digging the Trench
The first row of wall block needs to be at least partially underground. This means that a trench must be dug to allow room for the footer (6" compacted gravel) and for a few inches of wall to be buried. The trench should be dug approximately twice as wide as the blocks, and all loose or soft soil must be removed. It's crucial that the exact location of the wall is determined before digging the trench, as it will outline the path of the wall.
Building the Footer
#57 Stone or Crush n' Run is brought in and poured into the trench. It is then raked smooth and roughly leveled. We use a combination of running a plate compactor and hand tamps to compact the base to 100% compaction. For Crush n' Run this must be done in 3" lifts. We continue to add and compact material until we have reached our 6" minimum footer (6" is standard, very small walls may require less, and large walls can require more).
Leveling the First Course of Blocks
This is crucial. If the first course of blocks is not level, the wall will get more and more unlevel with each level of block that is stacked. We used small torpedo levels and 4' levels to check that each block is level itself, and that it is level with the block it's next to. If the footer is #57 stone we often level the base blocks in a bed of mortar. This adds strength and makes it easier to get each block perfectly level. If the footer is crush n' run, a small bed of masonry sand (1" or less) is added to allow for easier block leveling.
At this point, the wall should look something like this:
Stacking, Center-filling & Back-filling the Wall
Each course of wall must be backfilled with 3/4" gravel. Typically, we backfill 12-16" deep, but smaller walls require less and larger walls can require more. This stone allows water to drain down the back of the wall quickly, preventing hydrostatic build-up. In addition to backfill, block walls must be center-filled. The hollow portion of each block gets filled with 3/4" gravel to add weight and integrity to the wall.
As the wall is stacked, center-filled, and back-filled, it must be checked for level. Even if the base of a wall is perfectly level, imperfection in wall materials can cause levels be thrown out of line. If the wall level is thrown out of line we check to make sure the base is still level (it can be thrown out of level in the stacking process). If the base is not correct, it must be re-leveled. If the base is level, but the wall is thrown out of level in the stacking process, roofing shingles can be used to shim up blocks that are too low. Blocks that are too high can be slightly trimmed to bring them into line.
Following this process ensures the wall will last, and that it will have great aesthetics.
Installing Drainage
Behind the wall, in the gravel back-fill, a 4" corrugated pipe that is perforated (has holes in it) must be added behind the wall. It runs the length of the wall, and is normally designed to drain out the ends of the wall. This drain allows any water that is in the back-fill to seep into the drain pipe and flow out from behind the wall.
Larger walls may need drains installed periodically in the face of the wall (wall drain on Amazon). The drain pipe is plumbed into each wall drain in addition to flowing out each end of the wall. The additional exit points the wall drains add allows the water to exit from behind the wall more quickly, keeping it stable even in heavy rainfall.
After drainage is installed, the wall will look like this as it is stacked up, center-filled, and back-filled:
Each course of wall must be backfilled with 3/4" gravel. Typically, we backfill 12-16" deep, but smaller walls require less and larger walls can require more. This stone allows water to drain down the back of the wall quickly, preventing hydrostatic build-up. In addition to backfill, block walls must be center-filled. The hollow portion of each block gets filled with 3/4" gravel to add weight and integrity to the wall.
As the wall is stacked, center-filled, and back-filled, it must be checked for level. Even if the base of a wall is perfectly level, imperfection in wall materials can cause levels be thrown out of line. If the wall level is thrown out of line we check to make sure the base is still level (it can be thrown out of level in the stacking process). If the base is not correct, it must be re-leveled. If the base is level, but the wall is thrown out of level in the stacking process, roofing shingles can be used to shim up blocks that are too low. Blocks that are too high can be slightly trimmed to bring them into line.
Following this process ensures the wall will last, and that it will have great aesthetics.
Installing Drainage
Behind the wall, in the gravel back-fill, a 4" corrugated pipe that is perforated (has holes in it) must be added behind the wall. It runs the length of the wall, and is normally designed to drain out the ends of the wall. This drain allows any water that is in the back-fill to seep into the drain pipe and flow out from behind the wall.
Larger walls may need drains installed periodically in the face of the wall (wall drain on Amazon). The drain pipe is plumbed into each wall drain in addition to flowing out each end of the wall. The additional exit points the wall drains add allows the water to exit from behind the wall more quickly, keeping it stable even in heavy rainfall.
After drainage is installed, the wall will look like this as it is stacked up, center-filled, and back-filled:
Installing the Caps
The most satisfying part of building a wall is installing the caps. Caps are laid out dry on the top of the wall. Then, we make any necessary cuts to follow wall curvature. Finally, caps are glued down with block adhesive so that they won't fall and can handle foot traffic without flipping under the wait of someone walking along the caps.
The most satisfying part of building a wall is installing the caps. Caps are laid out dry on the top of the wall. Then, we make any necessary cuts to follow wall curvature. Finally, caps are glued down with block adhesive so that they won't fall and can handle foot traffic without flipping under the wait of someone walking along the caps.
PRICING!
Pricing is always dependent on the details. If the wall is very small and requires little excavation, little backfill, and no geogrid it will be much cheaper than a 4' wall that needs excavation, grading, and geogrid. That is why our pricing cannot be set without a visit to asses the details for each project. However, we can provide general pricing for concrete block walls (ask for pricing on other types of walls).
Common variables that may increase pricing are the following:
- lack of machine accessibility
- difficult or treacherous build location (hillside, up or down a steep hill, etc)
- height over 4'
- geogrid reinforcement
Basic Block Wall: $20 per square foot + $20 per cap
- doesn't require geogrid reinforcement
- minimal excavation & grading
- easy machine access
- short height
Standard Block Wall: $25 per square foot + $25 per cap
- doesn't require geogrid reinforcement
- minor excavation & grading
- 2-4' high
- easy/moderate machine access
Geogrid Reinforced Wall: $30 per square foot + $30 per cap
- will require extra excavation & grading
- requires geogrid reinforcement
- will generally be close to or over 4' tall
Pricing Example
For a wall that is 50' long and 3' high the pricing would be as follows (assuming standard pricing):
- 50x3 = 150 square feet --> 150x$25 = $3,750
- 50/1.5 (caps are 1.5') = 34 caps (33.3 rounds up to 34) --> 34x$25 = $850
- $3,750 + $850 = $4,600
*Pricing in the industry ranges from $15 per square foot to $35 per square foot. If a contractor's pricing seems low, check to see if they are following the installation guide laid out on this webpage (or refer to Belgard's installation guide for the block material chosen).
Common variables that may increase pricing are the following:
- lack of machine accessibility
- difficult or treacherous build location (hillside, up or down a steep hill, etc)
- height over 4'
- geogrid reinforcement
Basic Block Wall: $20 per square foot + $20 per cap
- doesn't require geogrid reinforcement
- minimal excavation & grading
- easy machine access
- short height
Standard Block Wall: $25 per square foot + $25 per cap
- doesn't require geogrid reinforcement
- minor excavation & grading
- 2-4' high
- easy/moderate machine access
Geogrid Reinforced Wall: $30 per square foot + $30 per cap
- will require extra excavation & grading
- requires geogrid reinforcement
- will generally be close to or over 4' tall
Pricing Example
For a wall that is 50' long and 3' high the pricing would be as follows (assuming standard pricing):
- 50x3 = 150 square feet --> 150x$25 = $3,750
- 50/1.5 (caps are 1.5') = 34 caps (33.3 rounds up to 34) --> 34x$25 = $850
- $3,750 + $850 = $4,600
*Pricing in the industry ranges from $15 per square foot to $35 per square foot. If a contractor's pricing seems low, check to see if they are following the installation guide laid out on this webpage (or refer to Belgard's installation guide for the block material chosen).
