Your Wet Basement Starts On The Roof

Go stand outside in the next hard rain. Umbrella, boots, five minutes. Walk the perimeter of the house and watch where the water actually goes when it leaves the roof. That five minutes will tell you more than any contractor's free inspection, because most wet basements aren't a foundation problem at all. They're a roof problem that takes the scenic route.

Run the arithmetic once and you'll never look at a downspout the same way. One inch of rain landing on 1,000 square feet of roof is roughly 620 gallons of water. A thousand square feet is a small roof. That water leaves through three or four downspouts, and if one of them dumps at the base of your wall, you've just poured a hot tub's worth of water into the soil eight inches from your basement.

So the order of operations goes like this: roof water first, grading second, window wells third, sump pump last. Do it backwards and you'll spend $12,000 on interior drain tile to manage water you could have sent down the driveway for eleven dollars in plastic extensions.

First, figure out if it's seepage or sweat

Not every damp basement is leaking. Some are just humid, and the fix is a dehumidifier, not an excavator.

Tape a 12-inch square of clear plastic sheeting flat against the damp part of the wall. Seal all four edges with good duct tape. Leave it 48 hours, ideally through a rain.

Moisture on the room side of the plastic means humid air is condensing on cold masonry. That's a ventilation and dehumidifier job. Moisture trapped between the plastic and the wall means water is coming through the concrete, and you keep reading.

That white crusty bloom on the block, efflorescence, is mineral salt left behind by water passing through the wall. It's evidence, not damage. Scrub it off, then watch to see if it comes back. If it does, water's still moving.

Gutters and downspouts do the heavy lifting

Get on the ladder and look in the gutters. A gutter packed with maple seeds and shingle grit doesn't overflow neatly into the yard. It overflows over the back edge, straight down the fascia and into the dirt at the wall, which is the single worst place on your property to put water.

Clean them twice a year. Spring after the seeds drop, fall after the leaves do. If you've got big trees and you're tired of the ladder, guards help, but they don't eliminate the chore. They turn it into a yearly one.

Then follow every downspout to its end. A splash block isn't a solution. A splash block moves water two feet and calls it a day.

You want the discharge at least six feet from the foundation, and ten is better. Rigid PVC buried in a shallow trench with a pop-up emitter at the low end is the clean version and runs maybe $40 a downspout in materials. Flexible corrugated extension on top of the grass is the ugly version and works nearly as well. Pick ugly and working over pretty and pending.

One thing the box store doesn't mention: buried extensions need a fall of at least an inch per ten feet, and they need cleaning out. Leaves get in. A hose and a sewer nozzle once a year keeps them honest.

Grading is a shovel and a Saturday

The building code standard is six inches of drop in the first ten feet away from the foundation. Most houses were built that way. Then the soil settled, somebody added a flowerbed, and now the ground tilts back toward the house.

Check it with a straight board and a level, or just lay a garden hose on the ground and look down the line. Standing water against the wall after a storm is your answer without any tools at all.

To fix it, use clay-heavy fill dirt, not topsoil and definitely not sand. You want the stuff that sheds water, not the stuff that drinks it. Build the slope, tamp it, then put two inches of topsoil and grass on top if you care how it looks.

Here's the mistake I see in nine yards out of ten: mulch beds ringed with plastic edging, sitting flat against the foundation, holding water like a bathtub. Mulch is a sponge. If you must have beds along the house, slope them away and keep the mulch four inches below the siding line.

And keep soil at least six inches below any wood. Termites don't need an invitation, but a dirt ramp is close enough.

Window wells and the one nobody checks

Basement window wells are a funnel by design. If the well fills, the window becomes a drain into your basement, and those windows were never built to hold back water.

Each well should have gravel in the bottom and a drain that ties into the footing drain. Dig down six inches in the gravel. If you hit hard-packed silt instead of a drain, it's clogged, and that well is a bucket.

Clear plastic covers cost about $30 and solve most of it. They keep rain, leaves and the neighbor's kid's soccer ball out. Get the domed kind that sheds water, not the flat panel that collects it.

The sump pump is the backup, not the plan

By the time water reaches the pit, everything upstream has already failed. Which is fine. That's what it's for. But treat it as a last line, not a strategy.

Test it every three months. Pour five gallons of water into the pit and watch. You want the float to rise, the pump to kick on hard, the water to drop, and the pump to shut off cleanly without short-cycling. Listen for the check valve to thunk closed. No thunk, no check valve, and water in the discharge line is falling right back into the pit.

Things worth knowing when you replace one:

• Cast iron body over plastic. It sheds heat better and lasts longer. Expect $150 to $300.
• 1/3 horsepower handles most houses. Go to 1/2 only if you've got a deep basement or a long vertical run.
• Vertical float switches don't hang up on the pit wall the way tethered ones do.
• Discharge outside, away from the house, and never into the sanitary sewer. That's illegal in most municipalities and it overloads the treatment plant during exactly the storm when it can't take it.
• In cold country, leave a small air gap or weep hole in the discharge line above grade so a frozen outlet doesn't deadhead the pump.

Power is the part that fails

Storms take out the electricity. Storms also deliver the water. Those two facts arrive together, which is why a $200 battery backup pump is one of the best-value purchases in the whole house.

A decent deep-cycle battery setup will run a backup pump for several hours of intermittent cycling. Check the battery water and the terminals twice a year, and replace the battery every three to five years whether it's failed or not. A dead battery in a backup system is worse than no system, because you thought you were covered.

Add a $15 water alarm on the floor next to the pit. It'll wake you up at 2 a.m., which is annoying, and cheaper than replacing the furnace.

When to stop and call somebody

Some of this isn't a Saturday project. Get a professional out for any of it:

Horizontal cracks in a block wall, or a wall that's bowing inward. That's soil pressure, and it's structural. Stair-step cracks wider than a quarter inch that keep growing. Water coming up through the floor slab in the middle of the room rather than at the wall joint. Any electrical work in a space that floods, which means GFCI protection and a dedicated circuit for the pump, done by a licensed electrician.

And if there's standing water in the basement right now, don't wade in to check the breaker. Kill the power at the main first, from outside the water, or call the utility. Water and a live circuit is the one mistake you don't get to learn from.

Everything else on this list is a shovel, a ladder, and a rainy afternoon spent watching where the water wants to go. It always tells you. You just have to be outside when it does.