Key facts: Flooded Basement Cleanup in Portland
- Portland's wettest months are November, December and January, and the city averages about 157 rainy days a year [1].
- The Big Pipe tunnels help cut combined sewer overflows to Portland's rivers, according to the city [2].
- In the 1964 Christmas flood the Willamette rose about 12 feet above flood stage in Portland [3].
- For Portland-area basement jobs: the EPA says significant water damage should be handled by experienced professionals [4].
Causes
Why Portland basements flood
Groundwater is the most common cause. Portland's rain falls steadily from fall to spring, and after weeks of it, the soil around foundations is saturated. Water pushes through cracks, old tie holes and the cove joint where wall meets floor. Basements that are dry all summer can show a damp band or standing water by January.
Surface water is next. Portland's big street trees fill gutters every fall, and overflowing gutters dump roof water at the foundation. Window wells fill and overflow. Downspouts that discharge too close to the house make it worse.
Floor drains are the third. In older parts of the city with combined sewers, heavy rain stresses the system, and a home's own lateral may be blocked by roots. Water that comes up through a floor drain is treated as contaminated. Plumbing failures, like water heaters and washers, round out the list.
Cleaning up a flooded Portland basement
- 1
Make it safe
Basement circuits are turned off; older basements often have the panel near the water.
- 2
Identify the water
Groundwater, surface water, supply-line water and drain backups each get a different response.
- 3
Pump and extract
Water is pumped out, then floors are extracted.
- 4
Remove wet finishes
Carpet, pad, the lower drywall and wet insulation come out in finished basements.
- 5
Clean
Concrete and framing are cleaned; drain backups require disinfection.
- 6
Dry and measure
Dehumidifiers run until concrete and wood read normal.
- 7
Address the cause
Gutters, downspouts, grading, window wells or a backwater valve before rebuilding.
Portland basement water: source, sign and fix
| Source | Typical sign | Common fix |
|---|---|---|
| Groundwater | Damp band at the wall base after weeks of rain | Interior drain tile and sump, or exterior waterproofing |
| Gutter overflow | Water at one corner during downpours | Clean gutters, extend downspouts |
| Window well | Water entering at a basement window | Clear the well drain, add a cover |
| Floor drain backup | Dirty water rising from the drain in storms | Clear the lateral; ask about a backwater valve |
| Water heater | Water spreading from the heater | Replace heater, add a drain pan |
Finished space
Finished basements and old houses
Many Portland basements were finished decades after the house was built, with framing and drywall against concrete that was never waterproofed. When water gets in, it sits behind the finishes. Cutting drywall a little above the wet line, removing insulation and pulling carpet lets the concrete and studs dry and lets the contractor see what is going on behind the wall.
In homes built before 1978, painted surfaces may contain lead, and some older materials may contain asbestos. [6] Ask about testing before anything is cut.
Rivers
River flooding and floodplains
River floods are rare but memorable in Portland. In 1964 the Willamette rose about 12 feet above flood stage, and in 1996 it crested at 28.6 feet and came within inches of overtopping the downtown seawall. Johnson Creek in southeast Portland has a long history of overbank flooding. If you live near the creek, the Columbia Slough or the river, check the city's flood maps and ask about flood insurance. See our Portland area page and the main flooded basement cleanup page.
Before cleanup arrives
- Stay out of basement water until power is off.
- If water is rising through a floor drain, stop using all water.
- Redirect downspouts if it is still raining and safe.
- For Portland-area basement jobs: move dry belongings upstairs.
- Photograph the water level and damage.
Belongings in Portland basements
Portland basements often hold decades of family history: boxed photos, holiday decorations, tools and old furniture. When groundwater or a drain backup comes in, sort quickly. Hard plastic, metal and glass can usually be cleaned and kept. Upholstered furniture, mattresses and cardboard that sat in groundwater or sewage generally cannot. Important papers and photos can sometimes be saved if they are separated before they dry stuck together.
Photograph everything before you throw it away, and make a list. An adjuster may want both.
Sump pumps and drain tile
Where groundwater enters every winter, interior drain tile around the basement perimeter carries water to a sump pit, and a sump pump sends it outside. The most common failures are power loss during the same storm that brings the water, a stuck float switch and a worn-out pump. Testing before November, keeping the pit clear and adding a battery backup address most of them.
If your basement flooded because the sump failed, tell the contractor. It changes little about the cleanup but a lot about what to fix before next winter.
Checking the contractor and the claim
Before work starts, look up the contractor on the Construction Contractors Board's license search. For the claim, photograph the water level, the source and damaged belongings, and ask whether your policy covers groundwater, sewer backup or flood, which are often treated differently from a burst water heater. The Oregon Division of Financial Regulation takes questions about insurers.
FAQ
Portland basement questions
Why does my Portland basement leak only in winter (basement job)?
Most of the city's rain falls from November through March. Saturated soil pushes water through cracks and the wall-floor joint.
Water is coming up my floor drain. What do I do?
Stop using water, keep away from it and treat it as contaminated. If neighbours have the same problem, report it to Environmental Services.
Is my basement in a flood zone?
The city publishes flood hazard maps, including FEMA maps. Homes near Johnson Creek, the Columbia Slough and parts of the Willamette should check.
Does homeowners insurance cover basement flooding here in Portland?
Sudden plumbing failures often are; groundwater, outside flooding and sewer backups often are not unless you have the right endorsement or flood policy.
Should I get a sump pump?
If groundwater regularly enters, interior drain tile and a sump are common fixes. Gutters and downspouts come first.
Why cut drywall that looks dry here in Portland?
For Portland-area basement jobs: water wicks above the visible line, and the concrete behind cannot dry while covered.
How long will my Portland basement take to dry?
Usually longer than upstairs rooms, because concrete holds water and basements are cool. Readings decide when it is ready for rebuilding.
Can I keep my basement carpet after a water heater leak?
Possibly, if the water was clean and extracted quickly. The pad is usually replaced either way.
Do I need to leave the house during basement cleanup?
Usually not for clean water. For a sewer backup, keep vulnerable people away from the basement until it is disinfected.