A homeowner in Wyckoff once asked me why our number was nine thousand dollars higher than the one she had in her other hand. Same square footage, same bluestone, same pattern. I told her the other quote was for a patio and ours was for a base with a patio on it.
She went with the other one. Four years later she called us to lift it and redo it. That cost more than the difference had been.
What fails
Patios in this part of New Jersey fail for two reasons, and neither of them is the stone.
Settlement. The base compacts unevenly under load and the surface follows it. You get a dip, water pools in it, and the dip gets worse every year because standing water softens what is underneath.
Frost heave. Water sits in the base, freezes, expands by about nine percent, and lifts whatever is on top of it. Then it thaws and the stone does not go back exactly where it was. Do that forty times a winter for five winters and the surface is a wave.
Both are water problems. Both happen below the stone.
What we put under it
Eight inches of excavation below the finished grade on a normal patio, more if the soil is bad. Northern New Jersey is heavy clay in most places, and clay holds water.
Then base stone, placed and compacted in lifts. A lift is a layer of three or four inches, compacted before the next one goes on. Dump eight inches in and run a plate compactor over the top and you have compacted the top three. The other five are still loose. That is what we find under most of the failed patios we pull up.
We use open-graded stone on most jobs now. It is angular and uniform-sized, and the voids between the pieces stay open after compaction. Water moves down through it and out. Dense-graded base with stone dust in it compacts to something close to concrete, which is strong, and it holds water, and holding water is the problem. ## Things worth asking any contractor
- How deep are you excavating?
- How many lifts, and are you compacting between them?
- Open-graded or dense-graded base, and why that one here?
- Where does the water go once it is through the base?
- What is the edge restraint, and is it mechanically fastened?
You do not need to know the right answers. You need to see whether they have one, and whether it comes quickly.
The honest part
A properly based patio costs more. On a four-hundred-square-foot terrace the difference is usually somewhere between six and twelve thousand dollars, almost all of it in excavation, stone and machine time.
If that number does not work, the right move is a smaller patio built properly, not a bigger one built on four inches of whatever was on the truck. We will draw you both.