Exterior French Drains in Knoxville, TN

It's one of the situations it was made for. A trench along your uphill side can catch water moving through the soil before it reaches the foundation. If most of what's coming down is surface runoff, a swale or diverter may do the job for less, and we'll look at both at the estimate.

Everything in the trench line and a working strip beside it gets disturbed, so beds along that wall usually have to be lifted. We mark the route at the estimate so you can see exactly what's affected and decide what to move or replant. Some people schedule the drain before new landscaping for that reason.

Daylight is the first choice whenever the lot falls enough to let the pipe come out at the surface downhill. On flat lots, or where daylighting would send water onto a neighbor or a driveway, a dry well gives it somewhere to soak in below ground. Karst soil takes water well in some spots and poorly in others, so we look at the site before settling on either.

That white deposit is usually efflorescence, salts left behind when water moves through masonry and evaporates. It tells you the block is getting wet from the soil side. An exterior drain or better grading on that side are the usual ways to cut it off, and the estimate will show which fits your house.

Buried lines are a normal part of exterior work. We ask what you know is there at the estimate, and buried utilities are marked before a trench is opened. Private lines like irrigation or old downspout pipe are found and worked around carefully, and anything that has to be moved is discussed with you ahead of time.

Ideally the pipe sits below the level where water is getting in, which on a crawl space is often near the footing. Shallow rock is common around Knoxville, though, and sometimes the trench has to stop where the rock does. We'll tell you what depth your lot allows and what that means for how much water it catches.

Fixing gutters, extending downspouts and correcting the grade should come first, and often they're enough. An exterior drain earns its cost when water is moving through the soil from uphill, the wall stays wet after the surface fixes are in, or the lot can't be regraded far enough. We'll tell you plainly if you're not at that point yet.

Usually that's a bad idea. Roof water arrives fast and in volume, and feeding it into a perforated drain can push it right back into the soil next to the wall. Downspouts work better in their own solid pipe to a separate outlet, and we lay both out so they don't interfere.

Fabric slows silt down a lot, and a properly sloped pipe keeps moving the fine material that does get through. Over a long stretch any drain can lose some capacity, especially in clay-heavy soil. Keeping the outlet clear and watching for water showing up where it hadn't been is your best early warning.

Sometimes, depending on how much room there is between the wall and the slope and whether a crew can get equipment in. Where access is tight, the trench may have to be dug by hand, or the job is better done from inside with an interior drain. We'll look at it in person and tell you what's practical.