Last updated November 17, 2025

Why is my polymeric sand washing out?

If polymeric sand is washing out of the joints, it is most likely attributed to one of these factors:

  1. Insufficient watering during the activation process

  2. Lack of compaction

  3. Overfilled joints

  4. Improper joint width

  5. Poor drainage

Any of the above issues can compromise the joints and the integrity of the polymeric sand. Let’s explore each.

Insufficient watering during the activation process

The water activation process is critical when working with polymeric sand. If G2 Gator Maxx or G2 Supersand was used, the rule of thumb for watering is to work in 30 square foot sections, watering for 30 seconds at a time. While this may feel like too much water, it’s not. In fact, even more water may be required depending on the joint size. The idea is to keep going until the joints repel water.

With Alliance’s G2 polymeric sands, you have one shot to get the watering right. So what happens if not enough water is applied? Typically a thin crust will form on the top of the joint, concealing loose, dry sand below. When this happens, the sand cannot set up properly and product can easily begin to wash out of the joints over time.

LACK OF COMPACTION

Every polymeric sand job needs to be compacted. After the initial compaction, the sand can drop anywhere from 30-50% further down into the joint. This means if the compaction step is skipped entirely, there won’t be enough material in the joints to properly bond and perform. Having a deficit of polymeric sand can cause weakened joints, premature erosion, and washout.

OVERFILLED JOINTS

Polymeric sand should never come into contact with foot or vehicular traffic. That’s the job of the pavers. When joints are overfilled with polymeric sand, the impact of traffic over time can lead to failed joints. After the proper amount of compaction, the polymeric sand should sit 1/8” below the chamfer of the paver. For irregularly shaped pavers or stones, you’d use the lowest point of the surface as a point of reference.

⚡️KEY TAKEAWAYS

  • G2 polymeric sands by Alliance should be watered in 30 square foot sections for 30 seconds at a time, maybe longer. This will prevent a thin crust from forming, which could ultimately lead to washout.

  • Every polymeric sand job needs to be compacted. After the initial compaction, the sand can drop anywhere from 30-50% further down into the joint.

  • After the proper amount of compaction, the polymeric sand should sit 1/8” below the chamfer of the paver. This will ensure the sand doesn’t come into contact with surface traffic.

  • Always follow the manufacturer’s recommendations for appropriate joint widths for each product.

  • The paved surface needs to drain properly in order for polymeric sand to perform as intended. Pavers or stones should be installed on a traditional base, which consists of a sand setting bed and 6” layer of compacted crushed stone underneath.

IMPROPER JOINT WIDTH

When installing polymeric sand, you should always follow the manufacturer’s recommendations for appropriate joint widths for each product. Joints that are more narrow than the recommended minimum run the risk of not enough sand making its way in. Joints that are wider than the recommended maximum run the risk of cracks, erosion, and washout due to the product not being able to properly bond.

The approved joint widths for Alliance polymeric sands are:

POOR DRAINAGE

Polymeric sand needs to cycle in order to perform optimally. When dry joints get wet, they will become flexible. As they dry out, the polymeric sand will self-heal and eventually harden back up when they dry again. Problems will arise when the joints can’t fully dry out. Erosion and washout is oftentimes a leading indicator or poor drainage. If you’re thinking about using polymeric sand, your pavers or stones must be installed on a traditional base system composed of two layers: the upper layer consisting of a maximum of 1” bedding sand and the lower layer consisting of a minimum of 6” compacted crushed stone. For overlay applications, drainage holes must be properly drilled into the concrete. (Note: We don’t recommend any of our polymeric sand products for concrete overlays that are wet set or thin set due to the lack of drainage.)

Related questions

My job got rained on during the rain-safe window. What should I do?

If a heavy downpour takes place within the rain-safe window, there’s a good chance that the polymeric sand will wash out of the joints and spill onto the surface of the pavers. This can create multiple issues, including not having optimal levels of sand in the joints and the potential for the product later drying on top of the pavers. In this case, you’d have to start from square one once the surface completely dries out and the weather conditions become optimal.

What if a light rain occurs immediately following my polymeric sand installation?

As long as the sand hasn’t washed out of the joints, you might be alright! You’ll need to wait for the product to completely dry in order to make an assessment.

What are some telltale signs that rain has compromised the polymeric sand joints?

If your job site is showing any of these signs, you might have to start your installation process over from scratch:

  • Sand has washed out of the joints

  • Sand has spilled over onto the surface of the pavers, creating a residue

  • Joints are bubbling or not hardening up after the recommended setting time