Basics

Drainage at the Bottom of a Sloped Drive

A drive that falls toward the house collects everything that lands on it and delivers it to the one place you least want it. The options, in the order they should be considered.

Updated October 2026 · Burlington Concrete

Plenty of houses sit below the road, and every one of them has the same problem in a different degree. The drive is a paved catchment, sloping the wrong way, and whatever falls on it travels downhill toward a building. Getting this right is a design decision made before anything is poured, and getting it wrong is expensive in a way that has nothing to do with the concrete.

Start by finding the low point

Before discussing channels, gullies or anything with a product name, establish one thing: where is the lowest point on the site, and is there a route from there to somewhere lower still.

This sounds obvious and it is routinely skipped. Drainage is gravity. Every solution on this page depends on water having somewhere to go after it has been collected, and if the foot of your drive is the lowest ground you own, collecting the water is only half a plan.

So the first question is not what to install. It is where the water will end up, and whether it can get there without a pump.

Fix the shape before you fix the symptom

The best answers here are shape answers rather than hardware answers, and they are only available while the drive is being rebuilt.

Ease the gradient where there is length to do it. A steep drop concentrated at the bottom is worse than the same fall spread over more distance, because water arrives faster and with more of it at once.

Put a level or reverse-falling section immediately in front of the garage. Even a short stretch that stops the descent, or tips gently away, takes the momentum out and gives an interceptor a fighting chance.

Crown or cross-fall the drive. A surface that sheds sideways as it descends delivers far less to the bottom than one shaped like a gutter.

Deal with the roof separately. Downspouts discharging onto a drive that already has a water problem are adding the entire roof area to it. Taking them somewhere else is often the cheapest single improvement available.

Then the interception

Once the shape is as good as the site allows, something across the foot of the drive catches what is left.

A channel running the full width is the usual answer, and the full width part matters: water finds the end of a short channel and goes round it. A gully at a low point is simpler and works where the fall can be shaped to bring water to one place.

Sizing, grating type and load rating all belong to whoever designs and installs it against your actual catchment, and we are not going to put numbers on a web page for something that depends entirely on area and gradient. What we will say is that undersizing is the common failure, and it is discovered during the first serious storm rather than during a normal week.

The part people leave until last

Where the collected water goes. This is the half of the job that is invisible, unglamorous and decisive.

Options are a gravity run to a lower part of the garden, a connection to an existing surface water system where one exists and permission allows, or a soakaway where the ground genuinely accepts water at the rate you need. That last one deserves scepticism on heavy ground: a soakaway that copes in August and fills in March has not solved anything.

Where the site is genuinely a bowl, pumping exists and is the answer of last resort. It is worth being clear-eyed about it: a pump is a mechanical device with a power supply, and the moment it is most needed is a storm, which is also when the power is least reliable.

Winter, which changes the sums

Every option above assumes water behaves as a liquid, and for several months here it does not.

A channel that works perfectly in October can be a solid bar of ice in January, at which point the drive is back to delivering meltwater to the garage door with no interception at all. Worse, the thaw arrives as a large volume over a short period, which is the heaviest loading the system will ever see, and it often arrives when the outfall is still frozen.

Two practical consequences. Grates and channels want to be somewhere the sun reaches if the site allows any choice at all, because a shaded channel stays frozen a great deal longer. And the discharge route matters more than the interception: a short run to daylight thaws; a long buried run to a distant soakaway can stay blocked for weeks.

It is also the reason snow piled at the bottom of a sloped drive is worth moving rather than heaping. A drift sitting over the one drain you have is a slow release directed at the exact spot the whole design was built to protect.

What this means for the concrete

Two practical consequences. The drainage design has to be settled before the slab is poured, because channels, gullies and the falls that feed them are built into the surface rather than added to it. Retrofitting means cutting a new slab, which is possible and is a poor use of money you have just spent.

And the second: if your existing drive already does this, replacing it like for like is the single most expensive way to keep the problem. The rebuild is the one opportunity to change the shape, and it should be taken.

Standing water does as much harm below a slab as it does at a threshold, and what water does to a base covers that half of it. Once the work reaches public ground the City becomes involved, and our walk-through of the kerb rules explains how. To have any of it quoted, start at concrete driveway.