How Do Pros Get a Patio Perfectly Flat? (The Screed and Laser System We Use)

You can always tell when a patio was leveled by someone who only used their eyes. One paver will be a little higher than the one next to it, and it causes you to trip. Sometimes there’s a corner that holds a puddle for a while every time it rains. The patio chairs don’t sit all the way flat no matter where you set them. By the time you notice these issues the pavers are already locked in, and the problem is the patio’s base underneath, not the pavers.

My name is Randy Thompson. I founded All Out Hardscapes & Lighting Solutions after leaving a career in aerospace, and for over 10 years we’ve been building patios, walkways, and outdoor living spaces all over Savannah and the Coastal Lowcountry. We serve everywhere from Wilmington Island to Savannah Quarters. I’m also a certified Techo-Pro installer, and the only one in the Lowcountry. Every one of the jobs I do gets leveled the same way. We use a steel pipe, an aluminum straight edge, and a laser level running the whole time.

How a crew gets a patio flat tells you a lot about how they work. The leveling is extremely important, and you don’t really see that part of the job being done. Well, I want you to see it. Once you know what each tool does and why each step is there, you’ll know enough to hold every installer to the same standard.

How Do Pros Actually Get a Patio Flat?

What they usually do is get some kind of rails and set them at a certain height so they can go and cut the stone to match the same height as the rails. The only rails we use are 1-inch steel conduit pipes that we lay down from one end to the other. To cut the stone, we just use an aluminum straight edge. That process is called screeding. It just means dragging a straight bar across two rails so it pushes off every stone that’s above the perfect height and makes it so we can see every low spot that needs more stone. Whatever sits between the two pipes ends up in one level section.

The laser is the tool that does the most. It makes sure the pipes stay perfectly level. We have a rotating laser that goes on a tripod so that the laser beam shines all around the job site and we always know we are level. We measure off that laser beam so that the back door is the same height as the far edge of the yard. The laser runs the whole time, and we double-check it every time we put a pipe down.

When one section is done, we do sort of a leapfrog thing with the pipes and everything to do the next part. We pull the pipe behind us, move it ahead, set it to the laser, and screed the next section. The pipes keep hopping across the patio until every square foot has been evened out perfectly between two rails.

The Screed System, Step by Step

There are two phases to this. First we build the structure. Then we build the finished surface the pavers sit on. Here’s our process for every patio we build:

• Spread the #57 base: This is clean crushed stone with no fine dust mixed in, the same rock used around a septic leach field, so water moves down through it.
• Set the pipes to grade: The conduit gets set in parallel runs, and each pipe gets set to exactly the right height, checked with the laser at both ends.
• Screed, leapfrog, and rake: We run the straight edge over the pipes, leapfrog them forward, and rake the whole layer out, filling the grooves from the pipes.
• Compact the full layer at once: A plate compactor, a heavy steel plate that vibrates the stone down tight, goes over the entire #57 layer. When it’s done, you could drive a truck over it without making a dent.
• Add 2 inches of 789 chip stone and screed it all again: We lay the pipes back down on the base, and the smaller stone gets flattened out even more than the first layer.
• Compact again, then set the pavers: After we compact it a second time, it’s like a solid concrete pad. The pavers go right on top, and the joints get filled with polymeric sand, which hardens once it’s wetted.

Screeding twice takes longer, but it’s the difference between a surface that stays flat and one that looks flat on install day and then looks uneven and unlevel shortly after.

Does “Perfectly Flat” Mean My Patio Will Be Dead Level?

No, and you don’t want it to be. Every patio we build has pitch and grade, meaning a slight slope that carries water off the surface and away from your house. If you sprayed a little water on one of our finished patios, you would watch it travel downhill and off the edge. A dead-level slab outdoors holds rainwater and gives you puddles and constant standing water after every heavy rain.

So when we say flat, we mean flat, but with a slope we purposely design. The surface is one flat surface with no dips, no humps, and no uneven pavers creating lips, and that surface is tilted just slightly, exactly the way we planned it. The laser is what gives us the same angle from one end of a big patio to the other. The pipes get set to the slope, and the straight edge makes sure it stays that way.

Why Not Compact My Patio Base in Thin Layers?

You can, but that means spreading an inch and a half of stone, running the compactor, spreading another inch and a half, and running it again, over and over. It is a real method, and we understand why some crews do it that way, but we don’t because of what we’ve seen it do to the stone.

Every time that plate compactor passes over a layer, it hammers the stone so hard that after a couple of passes it’s way over-compacted, which means the bigger stone starts breaking down into smaller stone. That’s not what you want. The stone is large for a reason: it’s an open stone with gaps for water to drain through, and crushed-down pieces fill those gaps and keep the base from doing its job. So we spread the full #57 layer, screed it, rake it, and compact it only one time. The stone stays whole, the base keeps those gaps, and it still ends up hard enough that you can drive on it.

Why Does the Stone Right Under My Pavers Matter?

The top layer is what the pavers sit on, so its shape decides whether the surface holds true or not. We use 789 stone, which is #7, #8, and #9 stone mixed together. The difference from standard #89 stone is that 789 is chip stone, with jagged, fractured edges. When we plate compact it, the pieces lock in tighter to each other.

Standard #89 is round. It’s more like fish tank gravel. When the gravel is round it rolls instead of locking into place, so when someone steps on it, it leaves a big divot, and that ends up under your pavers making them uneven. With chip stone, the surface we screed is the surface that stays, and that’s why the pavers can sit right on top of it and always stay flat and even.

How Can I Tell If My Patio Was Leveled Right?

A correctly leveled patio is easy to spot in several ways. Walk on it, sit on it, and watch it after rain. Here is what to look for once the job is finished:

• Paver edges are all even with each other, so your foot doesn’t catch anywhere.
• Water moves off the surface in the direction it was designed to go after a rain or a spray from the hose.
• Furniture sits steady wherever you set it, with no rocking chair legs or wobbly tables.
• The joint lines run straight and even across the whole patio once the sand is in.

There is one thing that worries homeowners during the install, but it’s actually no big deal. Before the joints are filled, the lines between pavers can look a little uneven. That’s normal. Once sand goes into all the joints, all those lines even out. Don’t judge anything until all the sand is in.

Is a Laser and Screed Rig the Only Way to Get My Patio Right?

No. The right tools on their own aren’t enough to build a flat patio. A crew with a laser that doesn’t do the grade checks, or that screeds a layer of rounded stone, can still give you a surface that’s uneven. And a crew compacting in lifts can still build a solid patio; we just don’t like what repeated passes do to the stone, which is why we do things differently.

Being flat also doesn’t make up for a bad base. A perfectly screeded top layer sitting on the wrong material, or on a base that wasn’t compacted, will still move and shift and cause problems. Leveling is just the finishing work. You still have to build on the right kind of base first. If you’re comparing installers, the leveling method they use should tell you how carefully they work, and the base they use tells you whether the patio is going to last for a long time or not.

What Should I Ask an Installer About How They Level My Patio?

If you’re holding two quotes that both say “compacted gravel base” and look about the same, the answers to these five questions will help you figure out the difference. Any installer who does this work carefully can answer these questions easily:

• How do you set your grade? Listen for a laser checked across the whole patio.
• What do you screed against? Rails set to that grade, like conduit pipes, give every section the same reference to work off of so everything is even.
• How much slope does the patio get, and which way does the water go? A clear answer means they planned for drainage and water.
• Do you compact the base in one pass or in lifts, and why? The reason matters more than the answer.
• What stone sits right under the pavers? Ask whether it’s angular chip stone or rounded stone, and why they chose it.

You’ll learn more just by listening to how confidently someone answers than from any line on the estimate. When we walk your property, we’re happy to answer every one of these before you sign anything.