Water coming into the garage, under the door or through the slab joint, usually means the driveway or the surrounding ground is sending water toward the house.
Garage slabs are often lower than the house slab and level with the driveway, which makes them an easy target for runoff.
What you may be seeing
- Water under the garage door after rain
- Wet floor along the slab edge or walls
- Debris and silt lines inside the door
- Water flowing down the driveway toward the door
- Water seeping at the joint between driveway and garage
- Stored items getting wet
First question: does water come down the driveway or in from the sides?
Watch during rain. Water flowing down the driveway to the door needs a trench drain or regrading. Water coming from the side yard needs grading or drainage there.
If water runs down the driveway into the garage
The driveway slopes to the garage or has settled near the door.
Possible causes:
- Driveway sloped toward the garage
- Settled driveway panel
- Downspouts emptying onto the driveway
If water comes in at the side walls
The ground next to the garage drains toward it.
Possible causes:
- Negative grade at the garage wall
- Beds trapping water
- Side-yard runoff
If water seeps up through cracks or joints
Saturated soil under or around the slab pushes water through openings.
Possible causes:
- High groundwater after rain
- Clogged perimeter drainage
- Open expansion joints
What you can check yourself
Only check these safely and after rain has stopped. Do not dig near marked utilities, and do not go near electrical equipment that is standing in water.
- Watch the driveway during rain
- Check the garage door bottom seal
- Look for downspouts emptying onto the driveway
- Check for a settled panel at the door
- Look at the side-yard grade near the garage
Answer 20 quick questions → to get a preliminary drainage assessment.
What a drainage professional may evaluate
- Driveway slope measurement
- Trench drain location and outlet planning
- Downspout tie-in options
- Side-yard grade and drainage assessment
Most common causes
Driveway slope
Water flows to the lowest point, the garage door.
Settled driveway
A sunken panel near the door creates a basin.
Roof runoff
Downspouts on the driveway.
Side-yard grading
Soil sloped toward the garage.
Worn door seal
Lets water past the door.
Possible solutions
The right fix depends on where the water comes from, where it collects and where it can legally and physically go. These are the solutions most often considered:
Trench (channel) drain
A grated drain across the driveway in front of the door, piped to an outlet.
Downspout drainage
Move roof water off the driveway.
Regrading
Correct the side-yard slope near the garage.
Concrete repair
Raise or replace settled panels, where appropriate.
Door seal and threshold
A threshold strip and new bottom seal for minor water.
When to call a drainage professional
- Water enters in most rains
- Stored items or finishes are damaged
- The driveway slopes to the garage
- You need a trench drain with an outlet
Frequently asked questions
How do I stop rainwater from coming into my garage?
Find where it comes from. Driveway water usually needs a trench drain or regrading. Side-yard water needs grading or drainage. A new door seal helps with minor water.
Does a garage trench drain need an outlet?
Yes. A trench drain must be piped to a legal outlet with enough fall, or it will fill and overflow.
Is a garage threshold enough?
Thresholds help with small amounts of water. They don't solve heavy driveway runoff.
Bottom line
Water in the garage is usually driveway or side-yard water. Intercept it before the door and carry it away.
This page is educational and does not replace an onsite evaluation. Conditions, codes and HOA rules vary by property.