What goes into a 20x20 paver patio

The breakdown, line by line

This is a patio on a level backyard, standard concrete pavers, running bond, no walls and no demolition. It is a typical version of this project on the flat tracts north of Ventura Blvd.

CMHA, the concrete paver industry group, publishes the standard a good bid should follow: a minimum aggregate base of 4 to 6 inches under walks, compacted to at least 98 percent of standard Proctor density, and a nominal 1 inch layer of bedding sand. The base and the compaction are a large share of the work, which surprises people, and it is the thing to understand before comparing two quotes. What moves each line on your lot is covered on what moves the price in Woodland Hills.

Common add-ons

How 20x20 compares with other sizes

Twenty by twenty is the sweet spot for a reason. It is the smallest footprint that holds a dining set and a separate seating group without the two colliding, and it is a size many people settle on when they plan a paver patio in Woodland Hills.

Now the part the tables cannot show

That breakdown assumes a level lot with somewhere for water to go. In Woodland Hills that assumption holds on one side of Ventura Blvd and falls apart on the other.

North of the boulevard, out in the post-war ranch tracts running north across the valley floor, the lots are flat and easy to work, but the ground is mostly clay and clay loam, and the heaviest of it, mapped as Cropley clay, is rated high for swelling. Water moves slowly through that clay rather than draining away through it. Build a patio base on saturated clay without a real drainage path, and the aggregate mixes down into the soil, the pad settles unevenly, and by the second winter you have a birdbath in the middle of your new patio. That is why the fabric line and the drainage line on the table are not padding. On these lots they are the job.

South of the boulevard, climbing toward Mulholland through the Santa Monica Mountains foothills, the ground is firmer but nothing is level. A patio this size on a hillside lot is not really a patio project, it is a small grading project with a patio on top. You cut into the slope or build out from it, hold the change in grade with a retaining wall, drain behind that wall so water pressure never builds against it, and only then start on the paver base. Add narrow winding streets that limit truck size, plus the City of Los Angeles grading permit that grading in the hillside grading area needs, and the same patio becomes a much bigger job. It is also, more often than not, the best outdoor space on the property once it is done.

How to read two quotes that are far apart

When one bid comes in far under another, the difference is almost never the pavers. Paver material is much the same from one bid to the next. The difference is base depth, how the base is built for your soil, whether compaction happens in lifts or all at once, and whether drainage got priced at all. Ask each bidder three questions: how deep is the excavation, what goes between the clay and the aggregate, and where does the water go. A crew that answers those clearly is a crew that has looked at your lot.

Also check what happens to your old slab. Many of the ranch houses here still have their original back patio, and demolishing and hauling it away is real work. If that is not on the page, it is coming later.

What the crew actually does on these lots

On a flat clay lot the crew digs out the soft material, puts fabric down between the native soil and the new aggregate where the plan asks for it, builds the base in compacted lifts, and sets a steady fall away from the house. If there is nowhere for that water to run, a channel drain or a dry well goes in the quote before anyone signs, not after the first rain. On the big Walnut Acres parcels, where the old walnut orchard land now comes in one to two acre pieces, there is usually a natural low point to work toward and plenty of room to stage material, which keeps the labor efficient even on large areas.

On a hillside lot the crew walks the grade with you first and says plainly whether the project needs a wall, an engineer, and a permit before there is any talk about pavers at all. If your property sits inside the Very High Fire Hazard Severity Zone that covers much of the area south of the boulevard, a good installer will also point out where a noncombustible paved surface near the structure does double duty as defensible space.

A number is only half the value question. How long these surfaces hold on clay is the other half.

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