A patio that floods during rain is often draining toward the house, or sits in a yard where water has no exit. Covered patios also take roof runoff from the patio cover itself.
Because patios are usually right outside a door, patio flooding can quickly become water entering the house.
What you may be seeing
- Water standing on the patio
- Water flowing toward the back door
- Water at the patio and house joint
- Lawn draining onto the patio
- Algae or staining
- Puddles under a patio cover
First question: which way does the patio slope?
Pour a bucket of water on the patio. If it runs toward the house or just sits, the slope is the problem. If the patio sheds water but floods from the lawn, the surrounding grade is the problem.
If the patio slopes toward the house
Water runs to the door and the slab joint.
Possible causes:
- Patio built with an inward slope
- Settled patio slab
- Added pavers changing the slope
If the lawn drains onto the patio
The patio sits lower than the surrounding ground.
Possible causes:
- Lawn raised over time
- Patio set too low
- Beds draining onto the patio
If a covered patio floods
The patio roof concentrates water.
Possible causes:
- No gutter on the patio cover
- Downspout onto the patio
- Cover sloping toward the house
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.
- Test the slope with a bucket of water
- Check gutters and downspouts on the patio cover
- See whether lawn or beds are higher than the patio
- Watch where water goes during rain
Answer 20 quick questions → to get a preliminary drainage assessment.
What a drainage professional may evaluate
- Slope measurement
- Channel drain layout and outlet
- Patio cover drainage review
- Yard grade survey
Most common causes
Inward or flat slope
Water has nowhere to go but the house.
Patio below the lawn
Lawn water flows onto it.
Patio-cover runoff
A cover without gutters or with a downspout on the patio.
Enclosed backyard
No exit for yard water.
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:
Channel drain
A linear drain along the patio edge or the house joint, piped to an outlet.
Downspout drainage
Pipe patio-cover and roof water away.
Regrading
Lower the lawn around the patio.
Patio slope correction
Mudjacking, resetting pavers or replacement where needed.
When to call a drainage professional
- Water reaches the door or enters the house
- The patio slopes toward the house
- Covered patio runoff floods the area
- The backyard has no exit
Frequently asked questions
How do I fix a patio that floods?
Correct the slope or intercept the water with a channel drain, and manage roof and lawn runoff around it.
Do pavers fix patio drainage?
Pavers can be set with the right slope, but they won't fix a patio that sits lower than the yard without other drainage.
Should a patio slope away from the house?
Yes. Patios should slope away from the house so water drains away from doors and the foundation.
Bottom line
A flooded patio is usually a slope problem or a yard problem. Fix the direction of water flow before it reaches the door.
This page is educational and does not replace an onsite evaluation. Conditions, codes and HOA rules vary by property.