Why Is My Patio Holding Water or Not Draining in the Lowcountry?

You walk out back the morning after a good Lowcountry rain, and you see a puddle sitting in the middle of your patio that should have drained off hours ago. Maybe you’re seeing this puddle in the same low spot every time. Maybe the whole surface feels like it’s holding a thin sheet of water you have to step around. It’s annoying, and it makes you think something underneath went wrong.

My name is Randy Thompson, and I started All-Out Hardscapes LLC. I’m the only certified Techo-Pro installer in the Lowcountry. Over more than ten years, my crew and I have built more than 150 patios, walkways, and outdoor living spaces all over Savannah and the Coastal Lowcountry, from Wilmington Island to Savannah Quarters, and out to Pooler and Richmond Hill. I have also pulled up plenty of patios that other people built, and standing water is one of the first things I look for.

Here’s the part I want to make sure you remember, and I will show you why. Water doesn’t sit on a patio for no reason. It’s there because the base underneath wasn’t built to move water in the first place. Once you see how a patio is supposed to drain, the puddle in your backyard will make a lot more sense.

So Why Is the Water Just Sitting There?

Because the base under your pavers is not draining. Just like with a house, a patio is only as good as its base or foundation, and that’s why most of the patios around here end up with standing water when it should be draining off. When you see a puddle on top, the real issue is in the base layer. The pavers aren’t the problem.

Technically the puddle problem comes from two things. The surface has settled into the places where the sand has been washed away, so water collects instead of running off. The second thing is that the layer underneath doesn’t allow water to drain out, so it just sits there. But both of those issues stem from how the base was built.

How Is a Patio Supposed to Drain in the First Place?

A patio gets rid of water in a couple of different ways. First, it sheds water off the surface. The patio should have a slight slope that carries water away from the house, so rain rolls off the patio. The second way is it lets water drain through underneath, and most people don’t think about that part of it.

The draining part is the most important, and you don’t want to cut corners on this. Think about your septic system for a second. When the crew installed it, they put number 57 stone all around the pipes. Number 57 is a clean, open gravel with a lot of open gaps between the stones, and they use it because it lets water drain right through it and out. It’s basically the same thing as a French drain. Water runs through open stone and gets carried off somewhere else instead of sitting where it’s going to cause damage.

A patio built right does the exact same thing as a French drain or septic system. The base turns into a big drain field. Water that works its way down through the surface is able to keep moving, and drains out to the sides and into the ground. But if you don’t have open stone underneath, that water has nowhere to go but back up, onto your pavers, where you are standing in it and it’s causing problems.

Why Doesn’t a Sand-and-Gravel Base Drain Here?

This is where most patios in the Lowcountry go wrong, and it’s worth understanding because it’s so common. Unfortunately we’ve had to pull up a lot of other people’s work to do repairs, and we’d say that about 9 out of 10 patios around here are built the same way. They put about three inches of crush-and-run gravel, which is a mix of crushed stone and stone dust that packs down hard, and then two to three inches of plain sand on top for the pavers to sit on. That sand layer is called the bedding layer.

That sand is the reason these patios fail. With the first hard rain, water starts working the sand up and out of the joints between your pavers. Once the joints are just open gaps, water runs down into the bedding layer and starts cutting little channels through it and washing it away. It’s the same as when you dump a bucket of water out on the beach and it carves a channel through the sand on its way down. The same exact thing is happening under the patio every time it rains.

And the crush-and-run underneath makes it worse, not better. Water can’t sink through that packed gravel and drain away, so it gets stuck in the sand layer and follows the slope of the patio, washing the sand out with it. Season after season, the sand just keeps washing out. That’s why the pavers start coming up at odd angles and dropping into low spots in only three to five years. It’s because the sand that held them level has washed out from underneath them. And those new low spots are exactly where the water now collects. The draining problem and the sinking problem are the same problem.

Does Our Lowcountry Soil Make It Worse?

It does, and that’s not in your head. Coastal Georgia gets heavy, frequent rain, and the ground here doesn’t always soak it up very quickly. Much of the soil around Savannah drains slowly below the sandy surface when it gets to the layer of clay. Our specific type of soil here around Savannah has that clay-like subsoil that water moves very slowly through, so the ground stays wet for a long time after a big storm, according to the USDA Savannah soil series.¹

What that means for your patio is that you can’t count on the ground alone to soak up the water fast enough, especially right after a storm when the ground is already really saturated. The base has to do the draining. When that base is just sand sitting on packed gravel, the water has no easy path out, the ground below is slow to soak it up, and the puddle on your patio is what you end up with.

When Is Standing Water Actually Normal?

Just because you see some water on your patio doesn’t mean you’ve got a problem, and we want to explain that so you don’t worry unnecessarily. After one of our heavy rains, a little bit of standing water is actually normal. But it should be pretty much gone within an hour or so and the patio is dry again if your base is working correctly. Don’t expect your patio to be dry almost instantly the way some parking lots are.

Just keep an eye out for water that doesn’t disappear in a short time. If you end up with puddles that are there for hours or even longer, that’s a bad sign. If puddles show up in the same spots every time, or if you’re also seeing pavers lift at angles or sand washing out from between them, that will tell you that your base isn’t draining water the way it’s supposed to. One puddle after a huge storm isn’t the same thing as a patio that holds water every time it rains.

And to be honest, if you already have a patio doing this, what it takes to set it right depends entirely on how it was built underneath. There’s no generic right answer for every patio, and anybody who quotes you a fix without looking at the base is only guessing.