Rip Rap, Outcropping, and Steel Seawalls: What Are They?

So you’ve made your decision—after assessing the state of your property’s waterline, investigating the effects of shoreline erosion, and learning about the protection a seawall provides, you’ve come to the conclusion that you’re getting seawalls installed, and you feel good about it. You’re sure of yourself. You know what you’re doing. At this point, you might think that the decision-making is for the most part over, and all that’s left for you to do is to hire a contractor and get it done. But then you start perusing company websites and realize there are different kinds of seawalls, and you can’t really tell what the differences are or what you need. How does stone outcropping work? What holds steel walls in place? What is rip rap and why is it called that? Suddenly you’re right back where you started, unsure of what’s right for your property and how to proceed.

That’s where we come in. Here, we’ll explain what the chief differences are between steel seawalls, outcropping, and rip rap, as well as what applications are best suited to each type of seawall, so that you can choose with confidence.

Steel Seawalls

This is likely what you’ve been picturing in your head when thinking of seawalls up until now. Steel seawalls are common throughout much of the Chain O’Lakes, and you’ll see a lot of these steel structures buffering the shorelines of waterways spreading down all the way through the Fox River. These are the most plain-looking but also the most versatile and the most popular of the varieties of seawall available

The installation of steel seawalls is a multi-step process. First, the crew must excavate the shoreline so that there’s enough space to work. Once the area is ready, construction begins of what is called a “dead man” structure. This is an underground support system built from seven- and five-gauge steel, galvanized steel, and steel round-stock tie-back rods, all of which comes together to brace your seawalls against further erosion.

Once this structure has been completed, the area needs to be filled. While some contractors might fill with soil, it’s better to fill with medium-sized #8 stone. Soil will soak up and hold onto water from rain and from the waterway, whereas stone will allow that water to pass right through. Once the stone has filled the space, it’s covered in a vented plastic sheet, top soil, a straw blanket, and grass seed. The plastic sheet prevents the soil from falling through the stone, and the grass regrows over the top so that it’s like the area was never excavated.


Outcropping is a wall consisting of rows of layered stone, usually in large flat pieces, that prevents runoff and thus protects the shore from erosion. This type of seawall is best used in low-wake, low-traffic areas. If you don’t like the spartan look of steel seawalls, you might instead consider outcropping for your shoreline protection needs. The use of irregular stone can give the shoreline a more natural and aesthetically pleasing look.

Installation begins in much the same way as that of steel walls—the shore is excavated to the right grade, and a filter fabric is put down to prevent soil from eroding away from behind or below the outcropping. Once this is in place, workers lay down the layers of stone, assembling the wall from stones like putting together pieces of a jigsaw puzzle. Generally these are flat pieces of rock blasted from limestone and averaging between 1,000 and 1,800 pounds, but there’s a lot of variance in terms of the height, shape, and the overall look of the outcropping. Each project is in effect tailor-made to fit that particular shoreline, taking into account both the property owner’s aesthetic preferences and the conditions of the lake or river that the shoreline borders. Your contractor should evaluate your property and work with you to determine what depth, thickness, shape, texture, and arrangement of stones is the best fit for your shoreline.

Rip Rap

The term “rip rap” originates from the noun “rap,” a series of knocks or strikes, and so rip rap is a series of fractured stones broken up into smaller pieces than would be used for outcropping. You’ve likely seen these arrangements of smaller rocks lining the edges of ponds and streams. In addition to being one of the most cost-efficient ways to protect your shoreline, rip rap offers the most organic aesthetic appeal, blending with the environment and riding the line between looking intentional and looking naturally-occurring.

As with the other types of seawall, the earth is first excavated to the right grade and the soil covered with a protective fabric before the stone is placed over the top. Rip rap using smaller 3” to 6” stones is ideal for use on small ponds and no-wake areas on lakes, while the larger 6” to 12” variety is better suited to rivers and inland lake shoreline. Rip rap is also used to line bridge abutments, pilings, and other shoreline structures that need to be protected from the elements to prevent erosion.

Which of these types of seawall is right for your property is dependent on a variety of factors, including but not limited to what kind of body of water you border (river, pond, lake, etc), the wake and traffic levels on the water, the landscape, aesthetic considerations, and your desired budget. It’s important that you get a contractor who, rather than trying to sell you on the wall that nets them the best returns, will communicate effectively with you and discuss with you the best options for your seawall installation so that you can make the most informed decision for your property.

If you still aren’t sure what sort of seawall is the best fit for your needs and want a bit of guidance, feel free to contact us at (815) 331-8830 or [email protected] with your questions. The professional staff at Seawalls Unlimited in McHenry are available to assess your property and provide quotes for all of the different seawall options described here. We’ll support you throughout your decision-making process so that you feel secure in having gotten your shoreline the best possible defense against erosion.

Seawalls Unlimited
2350 W. Rte. 120
McHenry, IL 60051
(815) 331-8830