Ashleigh Clarke Architects

How can architecture combat flooding?


Posted: September, 2020

Author: AC Architects

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Architect and flooding

Unfortunately flooding is a significant problem for buildings all around the world, and it is sad to say that many architectural treasures are included in this. However, while architecture cannot solve or even fully protect from the most deadliest floods it is possible, and necessary to take several protective measures that could mitigate damage and consequently save many lives.

So the first step would be to identify whether the home or building being designed is in an area at risk for flooding. This can be done by checking flood maps widely available online. If the site turns out to be at risk for flooding the architect and client can then decide if they want to relocate or if they would like to stay and take the necessary protective measures. If the latter decision, the architect would then advise appointing a civil engineer to design a drainage and flooding strategy that would then be submitted as part of your planning application. Without this information from the civil engineer the planning authority will not validate your planning application knowing your proposal will be in a high flood zone.

Elevate above the flood level

To start, architects should build the structure above the flood level, this is to minimise damage if a flood should occur. The flood level elevation for specific areas can also be found online using programs such as Estimated Base Flood Elevation Viewer ran by FEMA. With this information, architects can then discern how high the risk to the building could be, and what method should be put into place to sustain it. One common way of elevating is by building the structure on columns or even stilts. However, in other cases, the solid foundation can simply be raised higher. If more information is needed, it will be the architects job to assess the climate and flood history of the area and consult information available online on coastal construction in particular.

Build with flood resistant materials

Flood resistant materials are those which can last in contact with flood waters for at least 72 hours without significant damage. In a flood the water can be both hydrostatic (standing water) and hydrodynamic (flowing water), and in most likely cases it can result in displaced foundation walls, collapsed structures, floating fuel tanks and scouring. When we talk about ‘significant damage’ it suggests any damage requiring more work than cleaning or low-cost cosmetic repair such as painting.

There are ways we can prevent damages, and flood resistant materials must be durable and also resistant to excessive humidity. Here are some of the flood resistant materials;

  • concrete
  • glazed brick
  • closed-cell/foam insulation
  • steel hardware
  • pressure treated and marine-grade plywood
  • ceramic tile
  • water-resistant glue
  • polyester epoxy paint

Flood-proofing

There are two different types of flood-proofing; dry and wet. Dry flood-proofing helps prevent the entry of flood waters, whereas wet flood-proofing allows flood waters to enter a house. Waterproof veneer, sealants and coating’s also help prevent the water reaching the interiors.

A waterproof veneer consists of a layer of brick backed up by a waterproof membrane, helping to seal the exterior walls against water penetration. For the interior walls the architect should specify washable closed-cell foam insulation in the area’s below the flood level. As mentioned, coatings and sealants maybe applied to the walls, windows, foundation and doorways. This will help stop flood water from entering the house through cracks and openings.

Flood-proof equipment

All service equipment will need to be above the flood protection level, this is generally the best way to help keep it protected. This equipment includes; heating, ventilating, air conditioning, plumbing appliances and electrical equipment, including service panels, meters, switches and outlets. If these appliances are not considered, they can become severely damaged over time and will need replacing. Electrical equipment in particular can potentially cause fires if short circuited. This is why it is best to keep all equipment above flood level.

Keep the lawn away from the house

Another method an architect will use for flooding is to grade the lawn away from the house. If the lawn tilts towards the house, the rainwater will pool around the home. Conversely tilting it outward will direct the rainwater away. This is why the lawn should use a heavy soil that contains clay content and sand, allowing the surface to empty into a more appropriate place such as the street or gutter.

Foundation vents or a sump pump

Wet flood-proofing is to install foundation vents which allow water to flow through the home rather than around it. However, this could cause damage to the interior of the property. If the interior (normally a basement) is prepared using flood damage resistant materials, the damage can be limited. Similarly, a sump pump is a type of equipment that pumps water out of the basement where flooding happens on a regular basis. Sump pumps with battery backup are highly recommended to allow them to continue functioning when the power goes out.

Construction permanent barriers

Placing a barrier around a structure can prevent flood waters from reaching it. All barriers considered should be constructed from concrete or masonry. While this solution may seem like a simple task, both flood walls and levees require extensive maintenance and a significant amount of land and usable soil materials needed for the construction.

Sewer backflow valves

Finally sewer back flow valves prevent flooded sewage systems from backing up into our homes. This issue can be very common, and can cause damage that is difficult to repair and hazardous to occupants. Generally, gate valves are preferred over flap valves because they provide a better seal against flood pressure.

Author: AC Architects

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