Water standing in a Houston yard: regrade, gutters, or a French drain?

Fix the roof water and the grade before you buy a French drain. On most Houston lots where water sits against the house after a storm, gutters with downspouts carried well clear of the foundation, plus soil reshaped so it falls away from the slab, solve the problem for a fraction of what a drain costs. A French drain is the right answer on a smaller set of lots, and laid in gumbo clay with nowhere to send the water, it moves the puddle underground and leaves it there.

That order matters more here than in most of the country, because the thing being protected is usually a slab sitting on clay that moves when its moisture changes.

Why does standing water near the house matter so much in Houston?

Because of what is under the house. Most of the metro sits on expansive clay, the gumbo, which swells when it gets wet and shrinks when it dries. A post-tension slab is built to ride that movement, but it rides it best when the moisture under the whole footprint stays roughly even. Water that collects along one side of the house after every storm keeps that side wetter than the rest. Then August arrives and the same strip dries hardest. That uneven wet-dry cycle is the mechanism behind a lot of the cracked brick, sticking doors and diagonal drywall cracks that show up on older inner-loop houses.

There are second-order costs too. Wet soil against a slab edge or a sill plate is what subterranean and Formosan termites look for, and a termite treatment works against you if the ground beside it never dries. On a pier-and-beam house, water running toward the perimeter ends up in the crawlspace, where it rots sills and feeds mold under the floor.

So the goal is not a dry yard. The goal is that the first 5 to 10 feet around the house shed water away from the foundation, every storm, on its own.

What should I check before paying anyone?

Go outside during a hard rain. Not after it. During.

Watch where the roof water lands. On a house without gutters, a 2,500-square-foot roof sheds a lot of water in a Gulf storm, and it lands in a line along the drip edge, right beside the slab. On a house with gutters, look at where each downspout ends. A downspout that empties onto a splash block 12 inches from the foundation is barely better than no gutter at all.

Then watch where the water goes once it is on the ground. Does it run away from the house? Does it pond in a low spot along the side yard? Does the neighbor's yard sit higher than yours and empty across the property line? Does the street flood to the curb and back up the driveway?

Those 4 observations sort almost every drainage problem into one of 3 kinds:

• Roof water dumped at the wall. The commonest, and the cheapest to fix.
• Grade that slopes toward the house, or flat ground that cannot get water away. Very common on older lots where decades of mulch, sod and flower beds have built the soil up against the house.
• Water arriving from somewhere else: a higher neighbor, a high water table in a wet season, or a street and storm system that cannot take more. This is the case where a drain earns its money, and also where it most often fails.

Take photos and a short video. Anyone you hire later will price the job better if they can see it raining.

Are gutters really enough?

Often they are most of the answer, and they are routinely done badly.

A gutter only helps if the downspout carries the water somewhere it can leave. A downspout extension that throws water 5 or 6 feet out onto ground that slopes away is often all a house needs. Where the yard is too small or flat for that, the downspout connects to a solid buried pipe that runs to the street curb, to a lower part of the yard, or to a pop-up emitter at the swale. Solid pipe, not perforated, for this run: the job is to carry roof water away, not to leak it back into the soil next to the house.

Two complaints are fair. Gutters under a live oak or a pine clog and overflow, and an overflowing gutter dumps the water exactly where you did not want it. Guards help but are not maintenance-free. And many older Heights and Montrose bungalows never had gutters, so adding them is a design question as much as a plumbing one. On a house in a City of Houston historic district, gutters and downspouts on the street face can fall within exterior review, so ask before you install.

How do I know if the yard needs regrading?

Stand at the foundation and look along the ground. It should fall away from the house, noticeably, for the first several feet. If it is flat, or if you can see the soil or mulch climbing up the slab edge toward the brick, the grade is part of the problem.

The classic Houston version is a flower bed. Year after year of new mulch and soil raises the bed until it sits level with, or above, the top of the slab edge. Now rain soaks the bed and runs straight at the house, and the brick weep holes, the small gaps at the bottom of a brick wall meant to let water out, are buried. Pulling the bed back down and reshaping it to fall away costs a weekend or a modest landscaping invoice and fixes more foundation complaints than any drain.

On a larger scale, regrading means reshaping the yard so water moves in a shallow swale, a broad, gentle channel in the lawn, around the house and out toward the street or the back of the lot. A swale is cheap to build, easy to see, and has no pipe to clog. Its weakness is space. A narrow side yard on a 50-foot inner-loop lot may not have room to slope away from the house and still carry water to the street without spilling onto the neighbor.

Before you bring in fill, check with whoever has jurisdiction over the address. Adding fill or changing how a lot drains can require review in some jurisdictions and on some lots, especially anything in a mapped floodplain, and the answer differs between the City of Houston, the small cities inside the Loop, and unincorporated Harris County. Confirm with the city or county before the truck arrives.

When is a French drain the right answer?

A French drain is a gravel-filled trench with a perforated pipe in the bottom, usually wrapped in filter fabric. Water in the soil finds the gravel, enters the pipe and travels along it to an outlet. It is a good tool for water that is coming through the ground: a wet side yard fed by a higher neighbor, a slope that seeps after every storm, a lot where the water table rises in a wet winter.

It is a poor tool for roof water, which arrives too fast and in too much volume for a slow-draining trench. And it has 2 problems in Houston specifically.

The first is the clay. Gumbo drains very slowly. A French drain does not soak water into gumbo; it collects water and has to send it somewhere. That somewhere must be lower than the pipe, all the way along, and on a flat Houston lot it often is not. A drain that falls toward a low point with no exit fills up and holds water underground, right beside the slab you were trying to protect.

The second is the outlet. On a lot with no fall to the back, the realistic outlets are the street curb, if the jurisdiction allows it, or a sump pit with a pump that lifts the water out. A pump works. It also needs power, fails during the storm that knocks out power, and wants checking every year.

So the questions to put to anyone selling a French drain are simple. Where does it discharge? How many inches does the pipe fall along its length? What happens when the street is already full to the curb, as it is in a serious Houston storm? If the answers are vague, the drain will be too.

Will drainage work keep my house from flooding?

No, and this is the concession worth taking seriously. Lot drainage handles ordinary rain: the water that falls on your roof and yard and needs to get away from the foundation. It does very little against the kind of flooding Harvey brought in August 2017, when the streets, the bayous and the storm system were all full and water came in from outside the lot.

If the street in front of the house fills to the curb in a heavy storm, every drain you build depends on a system that is already full. A French drain to the curb cannot empty into a curb that is under water. If flood risk is the real worry, the questions are elevation, the floodplain designation of the address, and flood insurance, not a trench in the side yard. Many properties that were outside a mapped floodplain before Harvey are inside one now, and that is worth checking before spending on drainage.

A related trap: a homeowner who fixes their own ponding by aiming a pipe or a regraded swale at the neighbor's fence has not solved anything, just moved the water next door. Texas has law on diverting surface water onto a neighbor's property, and those disputes get expensive. Send the water to the street or to your own lower ground, and if the only way out crosses someone else's lot, talk to the neighbor and an attorney first.

What does a sensible order of work look like?

Start cheap and visible, and only bury money once the cheap fixes have had a season to prove themselves.

1. Clean and fix the gutters you have. Seal leaking joints, rehang sagging runs, clear the downspouts.
2. Extend every downspout. Carry the water at least several feet out onto ground that falls away, or into a solid buried pipe to a real outlet.
3. Pull the beds and soil down from the foundation. Expose the slab edge and the weep holes, and reshape the ground to fall away from the house.
4. Add gutters where there are none, after checking historic-district review if it applies.
5. Build a swale if water still ponds in the side or back yard and there is room to carry it to the street.
6. Install a French drain only for water that is clearly arriving through the soil, and only with a defined outlet that sits lower than the pipe.

Then wait for a few hard rains and look again, during the storm.

The order is not a rule. A lot that sits low with a higher neighbor on 2 sides may need the drain early. But on most Houston houses, steps 1 to 3 cost little, take a weekend or a short landscaping job, and either solve the problem or make it obvious that something more is needed.

Who should I hire for this?

It depends on which kind of problem you have. Gutters and downspout lines are a gutter installer's job. Regrading and swales usually fall to a landscape contractor with grading equipment. A French drain is sold by landscapers, drainage specialists and some foundation companies.

Be wary of a foundation company that arrives to quote a repair and leaves having quoted only a drain, or only piers, without asking about the gutters. Remember too that Texas has no state license for general contractors, and drainage contractors are no different, so references and photos of finished work carry more weight than a logo on the truck.

If the house is in for a larger project anyway, a remodel, an addition or a rebuild, drainage belongs on the drawings, not in a change order. Grading, downspout routing and the finished floor height relative to the yard and the street are decisions an architect or civil engineer makes once, on paper, before the slab is poured. The drawing set for a new house should show where the water goes. If it does not, ask why.