Frequently Asked Questions

No. Because soil and substrate have a higher suction pressure than stone wool, no water is extracted from the soil or substrate.

Suction pressure is a characteristic of the water absorption capacity. Among other things, this is determined by the capillarity and the amount of water present in the material. In the case of soil and substrates, this suction pressure is always higher than that of stone wool. Stone wool therefore cannot extract water from the ground.

Among other things, the density of Rockflow ensures a high load-bearing capacity. The basic material is stone wool, which has all the properties of stone. Vehicles can park on top of the system without the elements losing their shape or functionality.

Rockflow is available in various densities. The most commonly used density is 5%. The remaining 95% is therefore available for the absorption of rainwater.

Rockflow stone wool has an outflow speed of 100 metres/24 hours. Taking into account the k-value of the substrate, a system is always designed to be completely empty and available again 24 hours after a shower. If this is not achieved due to a low k-value, the system is designed to undergo sufficient deflation via a delayed discharge (pinch construction).

Thanks to the large infiltration surface of stone wool, infiltration even on poorly permeable soil types such as clay is an option. Water absorption and release in stone wool remains the same throughout the product’s lifetime. In the event of unforeseen events such as flooding, the system can also be completely cleaned.

More information about rainwater infiltration

Rockflow stone wool elements are made from the raw material basalt and recycled stone wool.

A swale is a water-permeable buffer that fills up with water in the event of rainfall and discharges it to the ground. A swale is often a ditch or trench with a water-permeable base.

A traditional swale usually consists of a layer of soil with plants. The swale collects the rainwater, and slowly releases it into the ground. But because the space is often limited, a swale must be relatively deep in order to be able to collect sufficient rainwater. A Rockflow infiltration system can be installed beneath the layer of earth and plants, thereby creating more space for the collection of water. Thanks to the stone wool elements, a swale containing Rockflow stone wool is also shallower than the traditional variant.

More information about swales

The permeability of the soil is expressed by the k-value, also known as permeability or hydraulic conductivity. A k-value of 1 means that a raindrop travels 1 metre in a 24-hour period. The k-value is an important value, as it maps out the permeability of an infiltration facility.

The k-value of Rockflow stone wool is 50 to 200 metres per 24 hours, depending on the type of stone wool used. The k-value of the Rockflow water management system is therefore comparable to that of coarse sand or fine gravel.

Although stone wool is a safe material, temporary irritation (itching) may occur when working with it. To minimise this, we recommend that you always take the following measures when working with stone wool products outdoors:

• Wear body-covering clothing (long sleeves and gloves);
• Wear a dust mask and/or safety goggles;
• Rinse off your skin with cold water.

More information about working safely with stone wool

The main difference is that stone wool used for insulation is made to be water-repellent, while a Rockflow element can absorb up to 95% of its volume in water.

More information on the infiltration of rainwater

There is currently no CE mark for Rockflow stone wool, partly because the combination of stone wool and water management is not yet standardised. Rockflow is expected to have the CE mark and Declaration of Performance in 2023. 

Yes, objects such as playground equipment can be placed above a Rockflow buffer. Please note: the buffer must not be damaged during installation and the forces of the devices must be well distributed over the surface. Please contact the Rockflow team for the specific installation.

The permeability of Rockflow stone wool is approx. 100 m/24 hours. Rockflow systems are always designed so that every system, regardless of its size, is completely filled within 15 minutes.The upstream supply is often the limiting factor rather than the water permeability of the stone wool itself. This principle remains the same for larger systems with multiple input channels.