Pittsburgh is a giant hilly area, so you can find plenty of retaining walls. If you’re thinking about building one – or dealing with one that’s already failing – here’s what you should know before you start getting quotes.
drainage, compaction, and engineering all determine whether your wall lasts
decades, or fails in two years.
Why Most Homeowners Call Us About Retaining Walls
There are really three main reasons homeowners reach out about retaining walls:
- Existing walls are failing – Whether they’re bulging in the center, starting to fall over from the top, or just visibly deteriorating, something is going wrong, and it needs to be addressed.
- Water issues – Water is the enemy outside for many structures, including for retaining walls. Water issues could bring about soil erosion from underneath the walls, drainage problems, and moisture getting into places it shouldn’t be.
- Creating new, usable yard space – People will have a hill in their backyard that comes right down to their back patio and feel like they don’t have any backyard space. We’ll come in and dig out the backyard and put a retaining wall there so homeowners can have a backyard they can actually use – for their family functions, entertaining, play, and anything else.
The Biggest Misconception About Retaining Walls
That’s the biggest thing – people think it’s easy, that you come in and stack some stuff up and it will hold the hillside up. In truth, there are a significant number of steps that homeowners don’t see or don’t know about prior to having a wall built that actually go into the process.
What Should My Wall Be Built Out Of?
We have multiple options that we lay out for the customer, covering a variety of concerns. First and foremost, aesthetics – what are we looking for? Are we looking to match existing retaining walls that are already there? Match the aesthetics of the house? Match the aesthetics of the landscaping?
| Material | Durability | Cost | Best For |
|---|---|---|---|
| Segmental (interlocking block) | Extremely durable, long-lasting | Mid-range | Longevity and holding hillsides |
| Timber (railroad ties) | Shorter lifespan, warps over time | More cost-effective | Budget-conscious projects |
| Natural stone | Varies by installation | Varies | Old-school, natural landscape look |
| Poured concrete | Very durable, long-lasting | Higher end (prices rising) | Function over aesthetics |
Segmental Retaining Walls
These are made out of interlocking block, Versa-Lok, things like that. There are many manufacturers of these, along with plenty of color options. We have books that we go through with customers to show different options and colors. For instance, there are options for weathered block, as well as block that looks like railroad ties but is made out of concrete, which is actually pretty cool.
This is your interlocking, designed, engineered system. It’s extremely durable, lasts a long time, and for the price point you get true longevity. It’s what’s going to hold up a hillside.
Timber Walls
Timber walls are built out of railroad ties or similar timbers. They aren’t going to last as long because they’re natural, being made of wood. They’re a little more cost-effective, so if you want to save some money, a timber wall is a good option.
Timber walls also require a little more upkeep because they’re out in the elements getting wet. The material starts to warp a little bit over time. You might have to reinforce it. We do them, but it’s worth understanding the trade-offs.
Natural Stone Walls
This is a palette of stones that we piece together. It’s more of that old-school, natural look. You can put smaller pieces of stone together, or they have pallets of giant, large stones that you can set in the ground with a machine for that natural landscape look.
Poured Concrete Walls
This is framed, a concrete truck comes in, and you just pour it. It’s not as aesthetically pleasing as some options, but it’s very durable – it’ll last a long time. And the way concrete prices are going, it’s probably a little more expensive than the other options right now.
When Does a Retaining Wall Need an Engineer?
Anything over 4 feet in height requires an engineer in Pittsburgh
We take care of everything for the customer. The engineer puts a blueprint drawing together with all the elevation changes, noting how many blocks need to be in what areas for the best long-term performance of the property.
An engineer will be focused on functionality rather than aesthetics – they’ll tell you exactly how much stone you need, how far back you need to dig for the drainage, the compaction rates, and things like that.
If you skip the engineering step, there’s a lot more chance of failure. We’re not permitted to build walls over four feet without engineering, and we won’t take liability for walls that aren’t properly engineered.
What to Look for When Getting Quotes
When you get three quotes, it should be an apples-to-apples comparison. Having someone come in and give a cheaper quote for just stacking block – that should raise some questions.
The bottom line: Ask your contractor these questions:
It’s an investment in your property. You might spend $20,000, but you don’t want to spend that this year and then in two years have the wall fail because someone didn’t install it correctly because you went with the cheapest price.
Retaining wall installation shouldn’t be based on price. It should be based on process.
If a contractor gives a price without a plan for how water will be factored in, you’re probably going to have problems pretty quickly.
The Part of Building a Retaining Wall That Homeowners Never See
It’s all about the excavation and preparation, and it makes the biggest difference in whether the wall lasts.
Buried Base Course
The base course of a retaining wall isn’t supposed to be exposed. We see that a lot where the bottom course of block is visible and you can literally see the dirt underneath it as you’re standing in the yard. That’s supposed to be buried below grade.
This immediately undermines the wall, causing water and erosion from
underneath because the stone isn’t far enough down into the ground.
Compacted Base
When you put the block down, you’re not putting it on dirt. The dirt is going to move. You have to put down a layer of aggregate underneath the block, and it has to be compacted.
We use gravel chips, basically, that are crushed up. You put them down, level everything out, and compact the space with a plate compactor so nothing will move over time. A lot of walls we see don’t have proper depth of base – or don’t have any base at all – and that’s immediately going to have the wall sinking and moving. You’ll start to see walls that dip and shift because they’re sinking with the dirt and mud as rain falls.
Drainage and Stone Behind the Wall
What people don’t realize is that the taller your wall goes up, the further back your drainage and stone have to go. If you have a four-foot wall, you might only be two feet off the back of that wall. But if you have an eight-foot wall, now you have to be four feet off the back, and that whole area has to be excavated out for stone and drainage.
Geo Grid
Anything over a certain height has to have geo grid. It’s basically a reinforced fabric that you put behind the wall in each layer that almost locks the stone and everything in place. You put a layer of block, then geo grid in between the next block, and it goes back into the stone. The stone goes on top of it with each course, and that helps interlock and keep everything in place.
⚠️ People cut corners here because geo grid is expensive. Not putting enough aggregate
behind the wall because they don’t think it’s necessary is also a costly mistake.
Homeowners don’t know any of that, so educating them on it is part of our sales process.
How Drainage Works Behind a Retaining Wall
If you have a perforated pipe behind a retaining wall, buried underneath the stone where you don’t see it, that pipe has to daylight somewhere, meaning it has to come out of the ground or out of the wall. The water can’t just stay pouring into the ground. It has to go somewhere.
That’s all it is.
You can take it to the road to drain down into a sewer in some cases, but municipalities don’t always love that. So sometimes you’re daylighting it in the middle of the yard with a specific drainage plan, or through the wall itself.
We put small slit drains in the wall that are visually appealing – not just a hole – and the pipe connects to the back so the water comes out of the wall into the front, where we can control where it goes.
What Affects the Price of a Retaining Wall?
The base preparation behind the wall stays consistent across the board. It doesn’t matter if you’re using the cheapest block or the most expensive block in the world – the prep work is the same.
Your price fluctuation comes from two things: size and material.
- Size – This factors in how much labor the project is going to take, how long the wall will be, and how high the wall will be.
- Material – There’s block that’s six bucks a piece, and there’s block that’s sixty bucks a piece, and they’re the same size. It really depends on the aesthetics, what you’re looking for, and what kind of budget you have.
Those railroad-tie-style blocks? They’re really expensive, but they also look very appealing. So it all comes down to what you value. Are you valuing aesthetics, or are you valuing function? That’s a big factor when it comes to retaining wall pricing.
Contact the Stockman Lawnscape Team
Stockman Lawnscape has been serving Pittsburgh-area homeowners for over 29 years.
If you’re thinking about starting a retaining wall project, contact us for a free consultation.
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