With floods washing up in several parts of Britain this winter, there is a lot of discussion about how to prevent and manage floods. It’s all very political, with accusations of government bodies not doing enough or flood defences being inadequate. As usual, climate change is carefully avoided as part of the official silence on the matter. For today though, I just wanted to highlight five different ways to make a house flood proof.
Most of these techniques are well established. Some of them have been used for millennia by riverine or coastal communities. As the weather becomes more extreme, more houses will be at risk of flooding and these techniques will become more important.
This is the oldest and most obvious way to build a flood proof house. If you must build near a river or the sea, just make sure you lift your building above the likely height of the flood waters. There are a number of ways to do that. You can build a house on stilts, a traditional form in many places. You can build it on a raised platform like a beach house, or on a bank of earth or concrete. Larger office buildings might put a sacrificial car park underneath. A treehouse could also fall into this category. Here’s a an elevated house from Thailand and one from New Orleans:
Rather than raise your home above the waters, a second common technique is to protect your home or property from the water by building a sturdy and waterproof wall. This can be done to protect whole towns and villages, but there’s no reason why it can’t be done on individual dwellings. Perimeter walls with watertight gates are one approach. You can also incorporate berms and walls into the landscaping, keeping the water out of a whole property or allowing the garden to flood while protecting the house. That’s what engineer Carl Canty did, below left, so his garden can be under three feet of water and his house is still dry. The example on the right is less subtle, but still effective.
3. Dry floodproofing
If you’re going to let the flood waters reach the walls of your house itself, you might want to make them watertight. This can be done with sealant, or building in a waterproof membrane. Doors and windows will need to be flood proof. Airbricks and utilities entry points can be raised or sealed. Essentially, dry waterproofing is all about keeping the water out of the building. Germany’s Hafencity, which I wrote about recently, uses this approach for properties on the waterfront. Those are some Hafencity storm doors on the right below, and a house in Grand Rapids demonstrating the principle on the left.
4. Wet floodproofing
Rather than keeping the water out of a building, an alternative approach is to let it in but minimise the damage it can do: fit a solid floor rather than wood, move power outlets up the wall and ensure that any unmovable furniture is made of a material that can safely take a soaking. Wet floodproofing is often used to retrofit flood-prone properties that the owners can’t sell, which is making the best of a bad situation. Houses built for it are much better, such as the house on the left below which is built to withstand a tsunami, or this waterfront hospital in Boston. Planned with climate change in mind, its lower floor has a swimming pool and non-essential services so that the whole thing can flood without interrupting patient care.
5. Floating homes
Second-guessing how far future floodwaters might rise is a dangerous game in an age of climate change. If your house can float, it’s guaranteed to always be above the water. One way to do it is to build on pontoons and have a building that’s always floating. Below is an ice-bound floating development in the Netherlands, which has many examples of waterborne architecture. Amphibious houses are slightly different. They’re on land and only float when there’s a flood. Britain’s first was recently completed, and here’s one in Thailand. These are more experimental, but we may well see more of them in future.