Building up with
timber

Low carbon redevelopment and extension of existing buildings

What is

Optoppen?

"Optoppen," a Dutch term translating as "topping up," refers to a construction method aimed at maximising the usable space in our cities through the addition of lightweight, low-carbon roof extensions.

Why

Optoppen?

Densifying urban neighborhoods through increased floor area provides a low embodied carbon solution that delivers new homes while funding retrofit and renovation efforts by reusing existing structures.

The

Optoppen

tool

A web based tool to assess the number of storeys and increased floor area that can be added onto your building.

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“Architects and engineers have long recognised that most of our existing buildings are structurally over-specified, capable of supporting additional load. Vertical extensions that use lightweight materials, such as industrialised timber, can add even more floorspace – and if they are bio-based, the carbon avoided, and the carbon locked away for the next 100 years of the building’s life, is a sell for organisations like ours, and for our tenants, who want to tread lightly.” - Frederic Schwass, General Projects
“By adding... floors to the building stock we already have, we’re able to densify our city in a sustainable way and provide much needed housing in our city, which in turn supports the local businesses, shops, venues and cultural sites.” - Lotte Terwel, Vice Mayor of Amsterdam Centrum
“For our cities to densify successfully, we need to focus on multi-home, rather than single-home buildings. Topping up is a key solution because it uses our current housing stock, infrastructure and facilities.” - Laetitia Nossek, Dutch Green Building Council

Optoppen

projects

Arent Janszoon Ernststraat 700

Ten sustainable homes added atop Arent Janszoon Ernststraat, boosting housing, reducing costs, and enhancing sustainability in Amsterdam.

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150 London Road

London Road, Kingston, gains 23 homes, including a CLT optopping with eight duplexes, showcasing sustainable and creative urban design.

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198 Contemporary Arts and Learning

Timber-frame optopping adds two storeys to a 1960s arts centre, achieving 70% less embodied carbon compared with steel frame.

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Policies

Current and upcoming policies for countries that have specific policies relating to Optoppen or encourage the use of timber for upward extensions

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