Spring is here, so let’s talk about french drains

Posted by Matt Buchanan

As any subscriber to our blog will tell you, most of what we blog about is prevention techniques that help homeowners lessen their odds of needing use our water damage services. And with spring finally here, now is an especially dangerous time for your home when it comes to flooding. Homes are constantly under assault from weather and under pressure from the systems and appliances within them. Eventually, something bad can go wrong. And while all the prevention in the world can’t guarantee you that you’ll never suffer flooding damage, it’s always a good idea to understand the specific threats your home has and research the best ways to defend against those threats. For this week’s blog post, we’re going to talk about a specific situation that can lead to flooding and a common solution that is sometimes required.


What are french drains?


French drains are a system of trenches and perforated piping that collects and transports surface and groundwater away from a home’s foundation and deposits it safely near a storm drain.  In many instances, a sump pump is used to get the water out from below the ground so it can exit away from the home. While most people think of an exterior french drain, many waterproofing contractors these days recommend an interior drain tile system instead.


Interior versus exterior


interior-french-drainage-systemExterior french drains require digging a trench down to the footings of the foundation so that any groundwater that is a threat to the foundation’s walls can be collected. In most cases, a sump pump is necessary to get the water back up out of the ground and away from the premises. The deep trench is backfilled with crushed rock and gravel and can be very difficult to excavate in the first place if there is any concrete patio or decking around the home. With an interior drain, the slab is excavated and the same process is done inside the home.  As we said above, now-a-days most contractors will suggest an interior drainage system because it’s cheaper to install and easier to maintain/repair should anything go wrong.


When are french drains a good idea?


Even a reputable waterproofing company will tell you that when it comes to keeping water away from your home, the simplest solutions are often the most effective. We’ve blogged about these steps many times, but the short and sweet is you should:

exterior-french-drain() attach downspouts to your gutters and make sure they deposit rain water at least 6 feet away from your foundation

() slope the grade of your lawn away from your foundation. The rule of thumb is 1 inch for every 6 feet.

In the majority of cases, these simple steps will keep ground and surface water away from your foundation and your home dry. But in some situations, these steps aren’t enough and the addition of a french drain may be necessary. These situations include:

() Homes built on hillsides where it’s impossible to slope the grade away from the home.

() Homes that are built on flood plains where the water table is high.

() Lawns that have a retaining wall built into a hillside that allow the water to pool next to the home.


How much do they cost to install?


Most drainage experts will charge for linear foot, depending on what type of system you need installed, how far they need to dig/excavate, etc. Costs can typically range from anywhere between $2,500 on the low end to over $10,000 on the high end. Is that worth it to you? That’s a question you have to ask yourself. When doing so, consider your home’s risk of flooding should groundwater get trapped next to your foundation. Another thing you must consider is the deductible you’ll have to pay if your home sustains flood damage.  Most people think they have a $1,000 deductible but are shocked to find out it’s either $2,500 or 1% of the home’s value. If you have a higher deductible, and you have a finished basement that is at risk of flooding, it may make a lot of financial sense to go ahead and bite the bullet and have french drains installed!


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