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BluWater Solutions Retention and Drainage Layer - 40mm
BluWater Solutions Retention and Drainage Layer - 40mm - Image 2

BluWater Solutions Retention and Drainage Layer – 40mm

A high‑capacity retention and drainage layer for green roofs, designed to store water efficiently while supporting high structural loads.

£27.29£22.74

Available in pallets of 225 units

  • High water retention capacity to support plant performance

  • Suitable for both intensive and extensive green roof systems

  • Robust HDPE construction with very high load‑bearing capacity

  • Interlocking design for a stable and secure drainage layer

  • Supports effective ventilation and rapid drainage during heavy rainfall

BluWater Solutions Retention and Drainage Layer – 40mm is a high-performance drainage and retention unit designed for use within intensive and extensive green roof systems. Manufactured from hardened high-density polyethylene (HDPE), it delivers excellent water storage alongside outstanding mechanical strength.

The profiled structure is capable of retaining approximately 15 litres of water per square metre, helping to maintain stable moisture conditions for planting. Excess rainfall is efficiently discharged through the drainage channels, reducing the risk of waterlogging during heavy rain events.

The unit features an interlocking edge design that allows individual sheets to connect securely, creating a stable drainage layer across the roof surface. Additional embossing on the upper profile promotes airflow between sections and supports effective drainage when used in conjunction with a filtration layer. Installation is straightforward and contractor-friendly, making it suitable for larger roof areas and more demanding green roof builds.

  • Product type: Retention and drainage layer.
  • Material: HDPE.
  • Embossment height: 40mm.
  • Unit format: Sheets.
  • Sheet size: 2 × 1m (2m²).
  • Weight: 2.3kg/m².
  • Water retention capacity: approx. 15l/m².
  • Compressive strength (without filling): approx. 400kN/m².
  • Maximum load with filling:
    • Profiles in maximum retention arrangement: up to 850kN/m².
    • Profiles arranged inversely: up to 1,400kN/m².
  • Durability: Approx. 50 years.
  • Colour: Black.

What is the Retention and Drainage Layer – 40mm used for?

It is used as a high-capacity retention and drainage layer within intensive and extensive green roof systems, managing water storage and excess drainage.

Where does this layer sit within the green roof build-up?

It is installed above the waterproofing and protection layers and beneath the vegetation layer or growing medium.

Does this product require a separate filter fleece?

Yes. The unit is not integrated with a non-woven filter fabric and should be used with a suitable filtration layer to prevent substrate migration.

How are the units installed?

The sheets feature an interlocking edge design, allowing them to be connected securely to form a stable and continuous drainage layer.

Trade and Commercial Customers

Get in touch to discuss your requirements and receive a bespoke quotation for your projects:

Alternatively, you can contact our team on 01904 757372 Monday – Friday, 8.30am – 5pm (excluding Bank Holidays)

Delivery is free of charge on all orders to the majority of UK mainland addresses*; you can select your preferred delivery date for Turf, Handy Bag and Bulk Bag orders in the checkout, before payment. Saturday delivery is available for a set fee of £72 per order (including VAT).

You will receive an email following your order confirmation which will advise you of the delivery method for your delivery address, i.e. ‘Tail lift & manual pallet truck’, or ‘Hiab’.  Further details can be found in our *Delivery Policy.

Please note, in exceptional circumstances, the delivery method stated may not be possible, in which case our Customer Service Team will contact you with an alternative solution.

  • Medallion Turf & Biodiverse Turf: Free delivery is available Tuesday – Friday for most addresses (EH postcodes-only: Monday – Friday). Saturday delivery is available  for a surcharge of £72 per order.*
  • Bulk Bags, Small/Handy Bags & Green Roof Kits: Free delivery dates are available Monday – Friday. Saturday delivery can be selected for a surcharge of £72. If bags are ordered with Turf, the available dates shown in checkout will be Tuesday – Saturday.*
  • Wildflower Turf: Delivery is free of charge Tuesday – Thursday. Saturday delivery is unavailable.* Wildflower Turf will be delivered separately to any other items on the same order.
  • Wildlife Planters, Green Roof Components & Green Roof Kits: Delivery of these products will be within 5-7 working days, Monday – Friday. A free delivery date can be selected at checkout. Slightly longer lead times may be required for planters where colour options have been selected.
  • Grass Seed & Fertiliser: Where these products are ordered with Turf or Bulk Bags we will endeavour to deliver them together, however if purchased separately they will arrive within 2-3 working days via courier, Monday – Friday.

Take a look at our Ordering & Delivery Frequently Asked Questions.

Fuel Surcharge

We have worked hard to mitigate the impact, but due to the current disruption to energy supplies a fuel surcharge of 6.5% will be added to all orders. We appreciate your understanding. Full details can be found in our Delivery Policy.

Further details coming soon…

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Important update: Temporary 6.5% surcharge effective 7 April 

At Rolawn, we are committed to maintaining the high standards of quality and service our customers expect, so we want to be open with our customers about a change that will affect pricing from Tuesday 7th April. 

This decision has been taken in response to disruption to energy supplies, which has led to significant increases in wholesale prices, affecting not only fuel and fertiliser but also costs throughout our wider supply chain. As a business that relies heavily on fuel for both transport and operations, these sustained cost pressures have become increasingly difficult to absorb.  

While we have worked hard to mitigate the impact, the scale and pace of recent price increases have now exceeded what we can sustain internally, and we therefore need to recover a proportion of these externally driven increases. 

From Tuesday 7th April, a temporary 6.5% surcharge will apply to all products.  

We know that any increase in price is frustrating, particularly at a time when many businesses and households are already feeling under pressure. That is why we want to be clear that this is not a decision we have made lightly, and not one we wanted to make. It has been introduced solely to help offset unavoidable cost inflation and allow us to continue delivering the quality, reliability and service standards associated with Rolawn. 

We will continue to monitor market conditions closely and will review this surcharge as soon as circumstances allow, providing reasonable notice of any changes. We recognise that any price increase is unwelcome, but this step is necessary to ensure the continuity and reliability of our operations during a period of ongoing uncertainty. 

We remain committed to providing the quality, reliability and service standards you expect from Rolawn, and we truly appreciate your understanding and continued support. 

If you have any questions, please contact our customer support team who will be happy to help.