The Greenhouse That Grows Legs

‘The Greenhouse That Grows Legs’ was designed by architects BAT Studio and built in Wraysbury, Middlesex, reaching completion in early December 2015. This unique building in an area which experiences frequent flooding incorporates a unique flood defence system in the form of hydraulic ‘legs’ that raise the building out of the reach of damaging floodwaters.

Constructed around a steel frame the building incorporates four integral hydraulic legs enabling the building to be raised 800mm above the ground if a flood warning has been issued. The design team, which included architects BAT Studio as well as structural and agricultural engineers with specialist knowledge in hydraulics and mechanisms, believe this small building is the first to have been completed utilising this concept.

The ‘greenhouse’ is located in the garden of proud owners Erica and Peter, who have incorporated a variety of measures into their lives to reduce the impact of floods since moving to live on the banks of the Thames, including owning an amphibious car. 

“We love our house by the Thames – the only drawback is the river floods. When we bought the house in 2000 we were told the flood risk was 1 in a 100 but we have flooded five times. Our living area sits well above the flood level however our undercroft garage and storage area floods dramatically. In 2014 we suffered the worst flood of a generation which prompted us to find a way to protect our possessions. We approached BAT Studio for a solution that could provide a safe refuge for bulky items during a flood but was also a useful space for the rest of the year.” Said Erica.

They initially contacted BAT Studio with the idea of building a ‘floating greenhouse’ - a garden building which would also provide safe storage for their possessions in the event of a flood. However during the design process the team decided a ‘lifting’ building offered many advantages over floating.

One key objective for the project was to achieve a building with the smallest step up into it as possible. This was both practical for the ease of quickly loading heavy items into the building but also for aesthetic reasons. For 99% of the time this building will be on the ground and functioning as a greenhouse. So it needed to be a beautifully designed small building first and foremost, and an engineering project second. To float the building would have needed to displace a substantial amount of water, meaning it would have required a large base. 

Another concern was that anything that gathered underneath the greenhouse whilst it was floating would remain there when the floodwaters receded. When the river floods, a lot of silt and debris is distributed around the flooded area. The fear was that at best this would leave the building un-level or at worst it could cause damage to the structure.

As built as a lifting building, when a flood warning is issued, the owners can pack the building with furniture and possessions at risk of damage, and safely raise the greenhouse via remote control. Once the floodwaters have subsided the building can remain in its raised position until all water and debris underneath has been cleared. The use of hydraulics also means the building always lifts level, irrespective on any uneven or changing loads within the building, another advantage over a floating design.

The structure of the greenhouse is formed from glue laminated timber sections. The columns are expressed externally on the buildings primary facade and have aluminium composite mirrors laminated to them. The result is an ambiguous visual effect, blurring the building and its contents into its surroundings. As the greenhouse becomes established and filled with plants, this effect of melting into the landscape around it will continue to improve over time.

Due to its location the 29 square meter building required planning consent. The design team understand that had the building not been capable of being raised on legs it may not have received consent due to restrictions on new building in the flood prone area. 

The design process included a significant amount research and development from all the team but following the success of this small project we strongly believe that this approach to building flood resilient buildings could be viable in many scenarios. The technology is low cost and easily scalable.