Retaining Walls


NPK IS THE LEADER IN RETAINING WALLS:

Construction and repair for the Bozeman area. We are able to construct walls out of all different types of materials. From boulders, stone, manufactured block, wood, and concrete.

Here is an image (with terminology) of the different type of walls that can be constructed.

retaining wall

The type of wall you or your contractor chooses is dependent of factors such as the height of the wall, the soil load behind the wall, where the wall is located, soil under the wall(stability issues), and appearance to name a few.

Most retaining walls in the residential and smaller commercial projects are either Gravity walls, or Anchor walls(wooden wall with deadman, or manufactured block with geogrid). This simply comes down to cost, and the size of the walls being built in this arena. Generally they do not become large enough to necessitate using the other wall types.

Experience matters:

It is extremely important that whoever you hire to construct your retaining wall. That they have the knowledge to properly choose the correct type of wall to build for the situation, and have the knowhow to go about it correctly. The last thing anyone wants is to spend money, time, and energy having a wall constructed just to have it fail a few years later. Then hoping the contractor is still around, and will guarantee their work.    

At their root retaining walls are simple structures, however if you start to look around town you may see a lot of existing walls that are bulging, leaning, or have failed. There are many reasons a wall might fail, but generally it comes down to either poor construction, or old age.
Poor construction can come in many forms. Such as improper wall weight or anchor system to the soil load behind the wall, improper drainage system, incorrect base construction, or improper back fill techniques. Any one, or combination of these can result in wall failure.

An image of the different types of possible failures:

retaining walls

Besides old age preventing wall failure is pretty simple. Just take the time to build it correct in the first place!

That is why we feel it is extremely important to hire a qualified contractor. Sometimes(but not all) building a wall correctly is not going to be the cheapest option. You may run into a contractor that isn’t aware of proper techniques, so they may skip vital steps in the construction process. Once the wall is built you cannot tell what they did under(base construction), or behind(backfill, anchor, and drainage) of the wall. It may appear to be a solid wall, but wait a year or two and things may begin to fall apart. In skipping certain steps in construction they can provide a cheaper price because they are not doing as much work or using as much product. Which makes the overall project price less expensive.

However, in the long run this is going to be more expensive than building it correct in the first place, because you will begin to have costly repairs and may have to build the entire wall over again if you experience complete failure.

Some build basics are:
1. Dig the soil down to 3″ to 12″ inches below where you want your base layer to start. This is dependent on many variables, but you need to start with a flat area the length of the wall.
2. Dependent on the wall type you will need to create a base layer of “roadmix” crushed aggregate gravel, or a concrete footer.
3. Lay down your first layer of wall build material – stone, block, etc..
4. Once that is done lay landscape fabric behind the stone and up the side of the hill.
5. Install a perforated drain tile the length of the wall at the base layer. Make sure this drain tile slopes from high to low.
6. As you build the wall you will be adding clear washstone as backfill. Shovel in backfill as you build the wall, one tier at a time. Don’t add all the backfill at the end—it won’t compact thoroughly. Tamp down the washstone as you go with a hand tamper. Behind the top tier of the wall add about 6 inches of topsoil.

Some of the different types of walls, and picture examples are discussed below:

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Typical cross section of the construction of a manufactured block wall:

Retaining walls

Manufactured Block

Manufactured block for retaining walls come in a large variety. Styles, colors, and sizes. Because of this manufacturers offer many different products.

These type of walls can be small and decorative. Or they can hold back entire hillsides. This type of wall would be a Anchored Gravity wall. We are using both the weight of the block and Geogrid in the build for an anchoring system.

In conclusion: They are your go to wall product if your looking for a polished look.

Highlights

  • Strong
  • Consistant size
  • More of an urban look
Retaining walls

Boulders

Boulder walls have an awesome natural look to them. They are also great for large hillsides because of their size and weight.

Generally boulders are locally sourced. We source our Boulders from a ranch just West of Bozeman. This helps blend the walls into the natural surroundings.

In conclusion: If you are in need of a wall, but do not want it to be the main focal point in your landscape. Boulder walls fit that bill nicely.

If your interested in purchasing boulders. Click below to access our store.
We have the lowest priced delivered boulders in the Bozeman area:

Highlights

  • Unique size and shapes
  • Natural look and feel
  • Long lasting
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Wood

Wood retaining walls are a great option if you need to have the walls completely vertical. Most of the other wall product options require the wall to step back as you build up.
These walls are Anchored retaining walls.

The building process of wood walls makes this the case. You use ‘deadman’ to anchor the walls. This eliminates the need for a step back.

Highlights

  • Ability to build vertical
  • Natural look
  • Match your homes wood style
Retaining walls

Cut Stone


Tumbled cut stone is a great way to go if your looking for an established finished look.
You can also create any size, or shape you can imagine.
Most of all this is great type of stone to use for walls, and stair systems.
For the most part Cut stone walls are gravity walls with a masonry component. We like to build these walls for decorative and design purposes. If you need a larger wall we feel its better to go with one of the other wall options. This has to do with build technicalities and costs.

Some examples of what you can do with this sort of product:

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Flag Stone Rock

Flagstone rock is another great product. Especially if your looking for the natural look. They are normally very unique pieces. Flagstones come in a variety of shapes and sizes.
Because of this these types of walls are suited better for smaller, decorative projects.
Flagstone walls will generally step back (or batter) as they rise a little more than the other products, because they normally do not have the sufficient weight to hold back heavy soil loads.
They can provide great accent walls throughout a landscape or garden.

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Below are some informational graph pictures of retaining wall construction:

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Image depicting ‘weep’ holes in a concrete wall. These holes are designed to mitigate water pressure and erosion.

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Dependent on the type of product you are using. Sometimes it is better to build two smaller walls instead of one large one. This will help decrease soil load behind the wall.

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Another good cross section showing the use of Geogrid anchoring system. Geogrid is essentially a deadman for manufactured block walls.

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To Conclude:

There is a wall type to suit a variety of needs and wants. Retaining walls can be industrial and at the same time decorative.

NPK can provide retaining wall services for any type of project however big or small. We have worked on large commercial jobs as well as residential ones.

Immediately get in touch if you have any questions. We would love to hear from you. Walls and other hardscapes are our favorite projects to do!