With flood washing up in several parts of Lagos this rainy season, there is a lot of discussion about how to prevent and manage flood. It’s all very political, with accusations of government bodies not doing enough or flood defenses and drainages not being adequate. As usual, climate change is carefully avoided as part of the official silence on the matter. Away from the brickbats, this article will focus on highlighting 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 be at risk 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 a 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.
Rather than raise your home above the waters, a second technique is to protect your home or property from the water by building a sturdy and a waterproof wall. This can be done to protect whole towns and communities 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 the whole property or allowing the garden to flood while protecting the house.
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. Air bricks and utilities entry point can be raised or sealed. Essentially, dry waterproofing is all about keeping the water out of the building.
Rather than keeping the water out of a building, an alternative approach is to let it in but minimize the damage it can do: fit a solid floor, move power outlets up the wall and ensure that any unmovable furniture is made of a material that can safely take a soaking. Wet flood –proofing is often used to retrofit flood-prone properties that the owners can’t swell, which is making the best of a bad situation. Houses built for it are much better.
Second-guessing how far the future floodwaters might rise is a dangerous game in an age of climate change. If your house can float, Its 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.