MetroPolder company: The Polder of the City

Cities are growing and the climate is changing. With this comes heavy precipitation, extreme heat,  prolonged drought, and less urban space for solutions. The MetroPolder company revives cities through smart water management, leveraging stored rainwater for cooling, growing, and fostering nature within the city. MetroPolder is a leader in advising, developing, and maintaining smart water storage in cities.

Our philosophy:

Rainwater is a resource. Not waste.

Rainwater is often seen as waste. Rain is free and is the source of all life. By removing it through a gutter, we make it waste. This does not have to be the case. Rainwater is useful in the city. It cools, feeds plants, supplements groundwater, and can replace drinking water for many applications.  The most direct example being irrigating the roof garden above the polder roof system; no drinking water is needed and it provides greater biodiversity! A true win-win

Polder Roof®

MetroPolder company developed the Polder Roof® as a solution for flooding in cities. We are still developing, but already we are cheaper than traditional solutions (larger sewers, stormwater tanks). Cheaper and beneficial for the city which is also getting even greener, smarter and more livable.

What is the Polder Roof?

In order to make smart water storage on flat roofs possible, we developed the world’s first Polder Roof concept. The Polder Roof transforms roofs into smart, controlled, water storage. In this way, the system is able to store all rain that falls on the roof and to dispose of or use at a later time. The Polder Roof serves as the foundation for a green roof, rooftop garden, or solar park. The Polder Roof enables irrigation, infiltration or a connection to greywater systems.

How does the Polder Roof® work?

The Polder Roof consists of a buffer system, internet connected weir and an online dashboard. If necessary, the roof is equipped with an embankment, possibly supplemented by a complete water-separating layer. The Sm^rt Drop weir measures and regulates the water level and the run-off. Information about the roof and operating system can be accessed via your personal dashboard.

The team behind this innovation ensures that all roofs are continuously monitored and operated at optimal performance. The Polder Roof represents a new layer in urban water management!

The Perfect Foundation for Every Surface

The surface of the roof is protected with a buffer layer, which provides space to store the water while forming a solid basis for a choice of application on top – from solar panel to roof park, from pavers to colorful floral mix.

Click here for the product sheet Polderdak® (SI units)

Automatic Retention Control

Polder Roofs are controlled by the Sm^rt Drop: a small weir which maintains the water level and a set of sensors to ensure that the system always functions safely.

Click here for product sheet sm^rtDROP (SI units)
Click here for product sheet sm^rtDROP (US customary units)

Online Dashboard

 We measure, report, and display everything we need to know to safely store (temporary)  water on the roof.

Click here for the Dashboard

A Regional Solution to Stormwater Management

Together with cities and universities, we work to transform urban centers into a smart grid for water. Call this a rooftop water-board. Resilio is an example of this.

Click here for Resilio’s website


Planning phase: The Roof Plan

During Design: Building Advice

Roofs offer opportunities for the climate adaptation of your municipality, region or development area. Many municipalities see these opportunities, but wonder where and how best to start. The Roof Plan can be drawn up at regional or property development level. With a Roof Plan:

• We determine where the possibilities for water storage on roofs exist
• You will immediately get practical tools for yourself and to work with other parties (private individuals, companies, housing associations).

For whom? Governments, City Planners, Water Boards, Housing associations

You want or have to store water on your lot, from the building envelope or sustainability policy/ambition. We will help you with a (winning) design that can also be executed:

  • Water storage advice: We will design to meet your water requirement or wishes (in VO or DO phase)
  • Engineering: We ensure that the water storage is properly secured in the construction or renovation process (in DO phase)

For whom? Developers, Architects, Contractors

During Construction: Setting Smart Weir

During Operating Phase: Management and Maintenance

The Polder Roof is built by an installation partner of your choice. We work with various local roof gardeners.

  • The sm^rtMILL or sm^rtDROP is installed by the roof contractor, MetroPolder provides the right settings and accessibility to the online dashboard
  • If desired, we will take care of a control of the Polder Roof during or after installation

For whom? Contractors, Green Roof Professionals

We maintain water storage, give you insight and if desired we report on your water performance:

  • Annual maintenance
  • Insight into performance through our dashboard and annual reporting
  • Data management

For whom? Roof Owners, Administrators


Click on the images below to view the projects.


Joost Jacobi
Project Developer

Merle van der Kroft

 Matthijs Monkelbaan

Jenno Vos
Maintenance and installation

Friso Klapwijk

Brian Schmitt
Project Developer

Bram Vulperhorst

Joris Hooftman
Monitoring and IT


Please note: from Monday the 2nd of August until Sunday the 15th of August many of our employees will be out of office due to summer holidays and therefore our replies may be delayed.

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    Polder Roof is developed in collaboration with: