How a patio drains (and why it fails)

A patio should shed water like a roof does: away from the house, off the surface and out. That comes from the slope built into it, not from sand added later.

Water that sits on a patio is almost always a grading problem rather than a stone problem. The surface is set to slope, the joints and base are planned to drain together, and the whole thing sends water somewhere it can leave. When any of that is off, water sits, the base below softens and pavers sink unevenly.

It's the single most common reason patios fail around here, and it's also the cheapest thing to get right at the start and the most expensive to fix later. Puddling at a door is usually the same problem showing up years in.

There are really four things that keep water moving: the slope of the surface, the pitch built into the base, the joints between the stones, and where everything eventually empties. Get all four pointed the same way and water behaves. Get one pointed backward and you get a puddle that never fully dries.

A lot of drainage work is invisible once it is done, which makes it easy to sell cheaply and hard to check. A swale dressed as planting or a run of drain stone under the lawn does the same job as a fancy system when it is laid out with the fall in mind, and it costs a fraction of what people fear.

Around a house, the number that matters is slope away from the foundation. A patio should fall about an eighth of an inch per foot, or a little more, away from the building and toward a place water can leave. That is gentle enough that furniture and feet never notice it and steep enough that a hard rain moves off the surface instead of standing on it. Flat is not neutral here. Flat is where water sits.

Where the yard has nowhere lower to send water, the fix is often a hidden one: a swale you would not notice, a dry well, or a perforated drain under the stone that carries water around the house and out to daylight. None of that is visible when the job is done, which is why it is worth asking where the water goes before a single paver is set.

One rule covers most yards: water should never be sent toward the house or left to sit against it. The patio should fall away from the foundation, and the ground around it should stay a little lower than the siding. If a downspout dumps right at the patio edge, that is worth moving or extending before the stone goes down, not after the first wet week shows you why.

Easiest test: after a heavy rain, look where the puddles sit. If the same spot is wet days later, the grade is telling you something before anyone digs.