Understanding the Importance of Compaction

June 27, 2023

Understanding the Importance of Compaction


Hello everyone, this is JW, and today I’m going to speak about understanding the importance of compaction.

Compaction of subgrade materials is crucial to a successful installation. Compaction in synthetic turf is accomplished by vibrating, tamping, and rolling imported aggregate materials.

Compaction establishes a solid base for driving nails and staples into the synthetic turf. It is essential that grading materials placed under synthetic turf be of quality and reach a minimum compaction of 80 percent.

If the underlying materials are poorly compacted, the synthetic turf may settle due to many reasons. Heavy foot traffic is one of them. When the turf area gets trampled by excessive foot traffic, having an unstable base will show depressions over time.

Heavy rainfall and excessive water intrusion can destroy subbases under synthetic turf, especially if the underlying base is poorly compacted.

When synthetic turf is placed in areas of excessive water run-off, this will allow water intrusion to soften the base. Even if your base is compacted to 95%, it is your duty as a craftsman to adjust the placement elevation to prevent ANY water from entering your installation. If you want to learn more about Drainage & Flooding in Synthetic Turf, click here to watch my last Vlog.

When starting out in the synthetic turf Industry, I recommend researching types of rock and sand materials that are available in your area. I also recommend speaking with the rock plant manager and/or qualified aggregate sales associate to provide you with information about the best mixture of rock and sand materials that are of quality and can reach good compaction rates.

Now that we’ve spoken about the importance of compaction, let’s look at a few pointers that all installers need to know to be craftsmen in this industry.

Exterior Edges
I always preach that seams and exterior edges are the first things a homeowner sees if done poorly. Exterior edges can make or break the beauty of your installation. I have seen edges that have sunk due to improper materials and poor compaction.

Seams & Compaction
“Subgrade stability has a lot to do with seam longevity”. Common failures to seam ruptures are caused by underlying soils lacking quality and form. Substandard subgrade materials that are unstable may cause the underlying subgrade to expand, contract, rise and/or settle.
For example, soils with expansive properties, high in fines, clay-like, and low in aggregate, will cause instability. This may cause the seam to move and/or separate over time.

We all know that playground surfaces take a beating. If the subbase is inferior, over time all the jumping, stomping, and pounding of the surface will lessen its longevity and create issues with its fall height requirements.

Turf Ribbons & Borders
When placing turf ribbons and borders, compacting the subbase to perfection is so crucial. Suppose the area that needs compacting is too small for a mechanical plate compactor. In that case, I recommend using a small sledgehammer and block of wood to ensure the surface is compacted to a minimum of 80%. If the turf ribbon is not compacted properly and settles, this may cause injury due to being a tripping hazard.

Putting Greens, Sand Traps, Bocce & Lawn Bowling
Putting Greens, Sand Traps, Bocce courts, and Lawn Bowling, they rely on the performance of their surface and need complete attention. I recommend taking your time and ensuring you don’t over-lift placing the materials, as it may cause soft spots on the surface. Remember… the surface is for “ball performance, so be patient and take your time with your subbase compaction.

Commercial Installations
Large Commercial installations require equipment that is large enough to handle serious compaction. Larger equipment will compact better and speed up production rather than placing small lifts with a small plate compactor. Suppose the commercial project requires *proctor testing (compaction readings). In that case, it is crucial to have an experienced grader who understands compaction readings and the water ratio needed for a successful outcome. Too much or not enough water will throw off the proctor. The proctor compaction test is a laboratory method of determining the optimal moisture content at which a given soil type will become dense and achieve its maximum dry density.

Pet Turf Areas
When installing pet turf areas, you must have proper drainage. This means having a compacted base that will allow the permeation of all fluids. Clean washed ¾” aggregates work great as a drainage base for pet installations or areas of poor drainage. You may need to top it off with an inch or so of DG, 3/8”minus or some chat to smooth out the surface, but be careful not to place too thick of the finer sandy material since these materials they retain moisture, they also harbor smell and will produce an everlasting odor.

Compaction Tools & Machinery
A plate Compactor is a mechanical compactor that has a flat steel bottom that slides on the surface while compacting. This is a must for all synthetic turf installations. You can rent mechanical compactors from most rental facilities. A Hand Tamper is a compaction tool that is used for all edges that a mechanical plate compactor cannot reach. It also is useful for compacting sidewalls or slopes and sand traps for putting greens. I recommend using a heavy vibratory plate compactor for all commercial or larger projects.

Placement of Aggregates
During my travels, I have noticed contractors not understanding how to place aggregates for compaction. I have witnessed installers placing and grading 1-foot “lifts” and then placing a vibratory plate compactor on top, thinking that would give them the optimum compaction; this is negligence on the installer. I recommend knowing and understanding the amounts, depths and lifts you import and how this depends on the machinery you need for optimum compaction. Highway builders with massive machinery only import 6 to 8 inches at a time. A standard walk-behind vibratory plate compactor will only compact 2 inches at a time and gain approximately 80% compaction. 80% is the minimum allowance recommended for the surface of landscape turf to lay on and this is written by the Synthetic Turf Council.

You may sacrifice quality for production if you import more than 2 inches at a time. Suppose you want to import 3-6 inches of imported aggregates at one time. In that case, I recommend using a heavier compactor to achieve a dense.. finished.. surface that reaches 80% or more compaction rate. Water has an important role in compaction. You need to know how much to saturate the imported materials to ensure cohesion of the layered compacted lifts. I always teach… “Don’t be a hoser”…. Get the smartest guy on the water hose. If the man on the hose isn’t consistent? Your compaction will not be either.

Below are my recommendations for how you should import and compact aggregates below your synthetic turf. Before importing subbase materials, remove any vegetation, rocks and debris. Smooth out all existing soils. If you are using a Pre-Emergent, I recommend placing a layer below your imported materials and then after the compaction is complete. This will prevent any future re-growth of vegetation that may want to sneak up through the drainage holes. AND PLEASE READ THE DIRECTIONS AND DO NOT CONTAMINATE OTHER LIVING PLANTS WITH THE PRE-EMERGENT GRANUALS.

FIRST LIFT –Prior to placing the first lift, I recommend saturating the existing soils so that the imported materials will bond to the subgrade below. This is where your #1 Hoser comes into place. Import approximately 2-3 inches of chosen aggregate materials and smooth them out evenly. After placing, leveling and smoothing the first lift, saturate the graded materials so that the water penetrates deep. DO NOT FLOOD AT ALL!

I recommend you allow the soaked areas time to penetrate deep prior to compacting. This will create a top crust for the compactor to ride on while the material below is being compressed. When most of the water has penetrated through the FIRST LIFT, compact the surface with the chosen vibratory plate compactor going in different directions. Clean the bottom of the plate compactor frequently to avoid “Dragging.” Dragging is when the soil sticks to the bottom of the plate compactor and slows the compactor down, and leaves grooves in the compacted surface. This is very important when installing putting greens. Repeat this process, soaking each lift with water until you reach your desired elevation.


If you are placing crushed drainage rock below your synthetic turf system, it is best to smooth and compact the crushed rock first and then place Decomposed Granite, Chat, or 3/8″ minus as a cushion, until you reach your desired elevation.

Whenever you are making the schedule to grade out your synthetic turf project, it is essential to check the national weather forecast for any rain. If you get to the point where your project is all graded and a major storm passes through, not only will it disturb compaction rates, but you may have to remove and replace the newly placed imported materials due to excessive flooding. 6 inches of flooded imported base may take days to dry out depending on the outside temperatures. Most imported materials that receive extensive amounts of water will cause separation between the aggregate and the fines and can no longer be used. I recommend synthetic turf contractors download the NOAA Weather Radar forecast App and stay informed on the weather.

“And remember… Your synthetic turf installation is only as good as what’s below it”… JW-OUT!!

Share This Story, Choose Your Platform!