Leveling Concrete Subfloors – WAKOL Leveling System

In the flooring professional’s world, encountering a flawless concrete slab is a rare occurrence. Ideally, every home would boast a smooth, flat subfloor, but in reality, that’s not often the case. From low spots to patch, high spots to grind down, to severely damaged slabs that warrant complete leveling, time-consuming challenges abound in subfloor preparations. As a result, leveling becomes an essential step in most flooring installations due to uneven subfloor conditions.

Prior to starting any flooring installation over concrete subfloors, it is crucial to adhere to standard requirements of levelness and flatness. Both manufacturers and the NWFA offer valuable guidelines for achieving the desired outcomes.

Consequently, understanding and implementing an effective leveling system and process holds paramount importance for a successful flooring project. Become well-versed in these techniques and ensure smoother installations for flooring professionals and homeowners alike.

Basic process of leveling a subfloor:

  1. Apply a moisture barrier
  2. Decide whether the subfloor needs spot patching or complete leveling
  3. Apply patch and/or primer and leveler
Watch our Pro Shop Talk episode for a thorough discussion of everything you need to know about WAKOL’s Leveling System. Get all the best tips from our technical director Daniel Elbrecht and Loba-WAKOL sales rep, Adam Morin.

Before you start leveling a subfloor, consider whether you need moisture protection or not. Get our full guide to WAKOL’s PU 280 on our website here.

Apply a Moisture Barrier

Conduct a concrete moisture test before leveling the concrete. Before flooring can be installed ensure subfloors are within the acceptable range. In most cases a moisture barrier will be necessary. It is our recommendation to use a moisture barrier even if slab moisture levels are within normal range because of the insurance it provides against future moisture problems.

Moisture issues are common and can surface years after installation, so why not address it at this foundational stage!

Applying a moisture barrier at its source gives you peace of mind that moisture won’t affect everything above it: the patch, leveler, glue, and flooring. Levelers are not designed for a high moisture environments and have limited ability inhibiting moisture. If moisture becomes a problem in the slab or migrates into the leveling products, it will eventually break down. A leveling system can contribute to the problem if moisture barrier primers are not also used.

For a deep dive into moisture mitigation, go to our guide about WAKOL PU 280. Utilizing products in the same system for your moisture barrier and leveling products keeps you warrantied and sets you up for success.

Decide if the Subfloor Needs Patched, Leveled, or Both

Before installing the flooring, thoroughly inspect the subfloor for high and low spots, holes, cracks, and seams that need attention. Grind down any high spots and ridges sufficient for leveler to cover them by an eighth-inch minimum. Use a laser level to accurately identify high and low areas, marking the target level on the wall for reference. Employ wood screeds along the walls to determine the exact height of the flooring during installation. For the middle of the room, utilize WAKOL’s leveling pins to mark the target height, ensuring precise leveling as it can be difficult to gauge target level and hit your mark.

Take your time in preparing to level, but remember that flat is more important than level.

Understanding Flatness and Levelness: Crucial Differences Explained

Distinguishing between flatness and levelness holds significant importance. Laser levels achieve absolute evenness in relation to the earth’s surface by providing precise measurements calibrated using gravity. On the other hand, flatness pertains solely to the subfloor’s surface plane and can differ from the level readings obtained.

When dealing with subfloors, the ideal scenario is to achieve both flatness and levelness. However, prioritizing a consistently even application of leveler across the concrete slab is paramount. Ensuring an even spread of the leveler prevents uneven deviations on the floor’s surface, which could cause issues like hollow spots, peaks along flooring edges, and other related problems once the flooring is installed.

While attaining perfect levelness is important, maintaining a consistently flat subfloor is equally critical to ensure a successful and problem-free flooring installation.

WAKOL’s Leveling System

Patch: WAKOL Z 501
Leveling Compounds: WAKOL Z 631 and Z 615
Primers: WAKOL D 3045 and D 3004
*Moisture Barrier Primer: Pu 280

What’s the difference between a patch and a leveler?

Use a patch to level off smaller isolated areas but not for large areas. Patch is ideal for holes, cracks, or chips in the concrete. Don’t overlook them at this stage as they’ll become hollow spots later. If the entire subfloor is unlevel, then use a leveler.


For small areas that need patched, use WAKOL Z 501. As a self-drying patching compound, it provides a smooth, highly durable surface for use over concrete subfloors. Dries within 30 minutes, after which can be installed over.

WAKOL Z 615 Leveling Compound, Dust-Reduced

Z 615 is very forgiving, easy to use leveler for those new to leveling. It also reduces dust associated with other levelers. Compared to Z 631, Z 615 has a longer working time of 30 minutes. This is the product to use if you have a smaller or an inexperienced team.

WAKOL Z 631 Leveling Compound

Z 631 is the most used of WAKOL’s levelers. It finds its level easily and sets up quickly – within 10-15 minutes. This means that you have to work fast before it sets. Keep reading for best practices, but the main recommendations are to apply it in batches and have a good team workflow. Ideally, you’ll have multiple people working in various roles to apply it.

WAKOL D 3045 Special Primer

A primer is important for two reasons: to help the leveler to stick to the substrate and to strengthen the leveler from impact. After PU 280 dries, it becomes slick, like a coat of finish on a floor. D 3045 has a sandy texture and pink color, that gives the leveler something to adhere to. The color enables you to see easily where you’re putting it and indicates that you’ve achieved complete coverage over the subfloor. You can apply with a quarter inch nap roller and it’ll dry within an hour.

WAKOL D 3004 Primer Concentrate

If PU 280 is not being used, you can apply the D 3004 primer concentrate directly to the subfloor. WAKOL recommends using the quarter inch Primer Roller. It dries within 2 hours, and once dried you can start the leveling process.

How thick can you apply leveling compound?

For both Z 631 and Z 615 leveling compound, the minimum depth is 1/8″ and maximum depth is 1″. Achieve optimal results by ensuring a uniform coverage of approximately 1/8″ thickness during application. If needing additional coverage beyond 1″, we advise applying a second coat after allowing the first coat to cure for 1-2 days. Remember to use D 3045 primer before adding the second coat.

How long does it take for the levelers to dry?

WAKOL leveling products dry fast. They are walk-on ready in 2-3 hours. Install flooring as soon as 24 hours after the your last application has dried.

What is the curing strength of these levelers?

WAKOL D 631: 4,500 psi
WAKOL D 615: 5,000 psi

For commercial projects both levelers perform well against heavy objects rolling across the floor,

To level a subfloor, it’s important that you are familiar with the directions for all the products you’re using. This guide is a good starting point, but it’s important to know the intricacies and limits of your leveling products.

How to Level a Subfloor with the WAKOL System

Once you determine the need to level a subfloor, follow the steps below to apply the leveling process:

  1. Read directions for ALL products you will be using
  2. Use WAKOL D 501 to patch individual areas
  3. Prime the subfloor, if needed
  4. Apply the leveler

Step 1: Read the Directions

Before you begin, take the time to read and understand the directions for all the products you’ll be using. Being familiar with the products is crucial in avoiding potential issues and ensuring a successful subfloor leveling project.

It’s basic, but true: the best way to avoid problems is familiarity with the products you’re using!

Step 2: Use WAKOL Z 501 for Patching

For selective leveling, utilize WAKOL Z 501 to patch individual areas such as cracks or voids in the concrete. Follow these steps:

  • Identify Problem Areas: Mark the spots that require patching.
  • Mix and Apply Patch: Quickly mix a portion of the Z 501 patch, as it sets within 10 to 15 minutes. Work it into the identified areas and mix more as needed, applying it strategically.
  • Allow Drying: Z 501 should be dry within an hour. Mix up more as needed and proceed to the next steps when no additional leveling is required.

After application, Z 501 should be dry within an hour. Proceed in applying the moisture barrier primer, and installing the flooring if no leveling is needed.

Using a primer creates the right foundation for the rest of the subfloor. If you use PU 280 beforehand, apply WAKOL D 3045. If you’re foregoing moisture protection, use WAKOL D 3004.

Step 3: Prime the Subfloor, if Needed

Consider these scenarios where a primer is needed:

  • A moisture barrier primer is needed when gluing down solid hardwood.
  • When using PU 280 along with a leveling product, it must be applied first before the leveler.

Scenarios that don’t require a primer:

  • If you’re only using the patching compound, there’s no need to prime first.
  • If you’re installing resilient flooring, a primer isn’t required.

Decide between two primer options:

  • If you’ve applied PU 280 moisture barrier and leveling compound, use D 3045 primer to create the bonding surface required for the flooring adhesive to stick.
  • If you’re foregoing moisture protection, use D 3004.

For either product, apply in a thin layer with a quarter inch nap roller. After an hour of drying you can apply the leveler.

Note: Primers are essential to effectively create the best surface for leveling products and adhesive to bond to while inhibiting moisture from migrating from the concrete to the flooring.

Remember: Moisture protection at this stage is important because months or years later unforeseen events could cause moisture to be absorbed by the concrete. Protection at the subfloor level is the best insurance against future moisture issues affecting your hardwood flooring.

For best results, it’s good to use a team-approach. Having someone mix up the leveler and another person apply it will help you to get the floor leveled quickly, before the leveler sets up.

Step 4: Apply The Leveler

Achieving an efficient workflow during the application of the leveler is essential. Check out this innovative method a contractor is using that pours out the leveler more efficiently.

Follow these tips for success:

Establish a Team-Based Approach: Designate roles for each team member. Every person should know their role and stay on task from bringing in bags and water, mixing it, to those applying it.

Proper tools and sufficient help is crucial when applying the product in a timely manner before it sets up. Once you start mixing bags and pouring product, there is no stopping.

Mix and Apply Promptly: Ensure the leveler is applied evenly and consistently in a timely manner.

Whoever is applying the product should have some experience with gauge raking, pulling it, and making sure it’s flat. No one starts as an expert and must learn by trial and error. Even if you’re experienced, it can still take time to get a rhythm going.

Drying Time: The leveler will dry within 2-3 hours, and you can begin the flooring installation after 24 hours.

For applications requiring more than an inch of leveling, break it up into two separate pours allowing sufficient drying time (24-48 hours) between first and second coat. Use D 3045 primer before applying the second coat.

By following these steps and using the WAKOL System, every job can be a learning experience and incredibly rewarding. Seeing the end product look like a level, glass surface is real satisfaction giving you peace of mind that you did it right.

The most common mistake when using a leveler, is applying it too thick. This can create bubbles and extend the dry time. Keep reading for more mistakes to avoid so that you get the best level on your subfloor.

What are some common mistakes to avoid using WAKOL leveling products?

The most common mistake is applying the products too thick – which produces excess bubbles and extends the time it takes it to dry.

For both patching and leveling products, don’t add more water than necessary. Typically, it’s 4-5 quarts per bag, but it depends on the product. If it looks milky, that’s a sign that there’s too much water. Excess water won’t let it cure properly or become as hard as needed.

As for the process, know where you need to fix before mixing the product. Have your game plan set and double check it so that you can accomplish it in a timely manner. Especially for larger jobs, plan out the application and communicate it well to your team. Make sure everyone knows what role they play and the proper steps to accomplish each task.

A successful leveling job happens when you have your system dialed in and everyone involved is working together. Only then can you look back on a leveling job well done and get started installing your beautiful flooring!

Get WAKOL’s Leveling System at one of our Pro Shops!

Find a Pro Shop near you and start using this system today. We’re here to help with any questions you have or connect you with a local WAKOL rep to walk you through this system.