Basement drainage
Water in a basement needs a path out. The simplest path is usually the one outside, so start there.
Basement drainage is any system that gives groundwater and roof water a way to leave before it reaches your floor or walls. There are four main ways to do it. And they work at different points along the route the water takes.
This page prints no prices. It explains how each approach works, so you can compare plans on what they do.
Start with the water you can see
Most basement water starts as rain that lands too close to the house. The roof sheds it into gutters, and the gutters drop it at the wall. Soil that slopes toward the foundation finishes the job.
Fixing this is simple compared with anything underground, and it reduces the load on every other system. The grading and downspouts page covers it in detail. Take a position: if you have not done this first, do not sign for anything else yet.
The four approaches
- Surface control: grading, gutters and extensions that keep water from arriving.
- Exterior drains: a perforated pipe in gravel along the footing, carrying water away from the outside of the wall.
- Interior drains: a channel along the inside edge of the floor that catches water and sends it to a sump.
- The sump pump: the pit and pump that lift collected water out and away.
How exterior and interior drains differ
An exterior drain stops water before it reaches the wall. It means digging down to the footing, so it is the biggest job of the four. The drain tile explained page covers how the pipe and gravel work.
An interior drain accepts that water will arrive and deals with it inside. It is easier to install and does not dig up the yard. It does nothing about water pressure against the wall. The interior vs exterior waterproofing page compares the two in full.
The sump pump is the last step, not the first
A sump pump is only as good as the drain feeding it and the power behind it. If the pump runs all day, something upstream is wrong. If it fails in a storm, you need a plan for that too. The sump pump failure page covers what goes wrong.
How to choose
Match the approach to the cause. Water that appears after a rain, near a downspout or a low spot in the yard, points to surface control. Water that rises through the floor or along the wall joint in wet seasons points to groundwater, and that is where drains and a sump come in.
Ask any contractor to explain how their system moves water out and where it ends. A good answer names the exit. A vague one is a warning.
Where to stop and call someone
Do not dig beside a foundation wall that is cracked, bowed or leaning. That is a structural question for a licensed structural engineer. An independent one has no repair to sell you. Local rules decide where you may discharge pumped and drained water, so ask your building department.
Frequently asked questions
What is basement drainage?
Any system that gives water a way to leave before it reaches the floor or walls: surface control, exterior drains, interior drains and a sump pump.
What should I fix first for a wet basement?
The water outside. Gutters, downspout extensions and grading that slopes away from the house are the simplest changes and reduce the load on everything else.
What is the difference between interior and exterior drains?
An exterior drain intercepts water outside the wall. An interior drain catches it inside, along the floor edge, and sends it to a sump.
Do I always need a sump pump?
No. A sump pump is needed where drains collect water that cannot flow out by gravity. It is the last step, not the first.
Where does the drained water go?
It must reach a safe exit, such as daylight on lower ground or a connection your town allows. Rules are local, so ask your building department.
Sources
What this page explains is based on these official sources. If you check one and it does not match what you read here, send it to us and the article gets corrected.
- US EPA. What You Can Do to Soak Up the Rain
- US EPA. Soak Up the Rain. Managing stormwater around a property