A Flagstone Patio Replaces an Old Rotten Deck

A Denver area carpentry client of mine was looking at a replacing an old deck. Years and years of weather and a slack maintenance plan had put this deck into a state of ugliness and decay. Its close proximity to an irrigated flowerbed provided the death sentence. It was time for some deck

Posted 5:29 p.m. Oct 12, 2012 — Updated 5:29 p.m. Oct 12, 2012

We opted to install a flagstone patio as a replacement. Flagstone is a good choice for those that want a lower maintenance option than a hardwood deck.

The First Steps

Before the flagstone project came to life, the decaying mess of the old deck needed to be removed. This work is pretty straightforward. We brought in a 3 yard dumpster and I dove in with my reciprocating saw. Cutting the old wood into manageable dumpster sized pieces is pretty easy. Dragging them around the house to where the dumpster was located was a bit more work. That long path was further put to the test, as the bulk of the patio materials were also hand carried to the back yard. Once the rotten lumber was removed the old (undersized) deck footers were then removed. Here I was glad the previous builder used methods that were wimpy compared to my normal building methods. Some of those footers were only a foot deep or so, well below the 3 feet required by code for proper frost depth.

The Containment Field

In a lot of patios the final grade is designed to match the surrounding yard. In this project the owner plans to do some additional landscaping work that will enhance the grass component of the back yard. Nearby tree roots and erosion left parts of the yard with an irregular soil profile. The future plan is to bring in fill to correct some of these leveling issues. Normally one would dig out soil, then add a crushed stone base to create a flagstone patio. Here I built a landscape timber frame that was then filled with the crushed stone. This served two purposes as it contained the patio area, and eliminated the need to haul away soil etc. The timbers were lap jointed and set with lengths of rebar to provide a strong and long lasting frame.

Crusher Fine Base

Crusher fines are a mix of fine gravel and sand sized particles. This material makes an excellent substrate, as it is firm and strong when compacted, and far less prone to washing out than plain coarse sand. This patio area is in the neighborhood of 200 sq. ft and about 2 ¼ yards were brought in to level the space. This material was man hauled in using a lot of 5 gallon buckets. It would have been nice to use a backhoe but the fence and gate configuration did not allow this type of access. Aside from the great exercise it provided, laying down the gravel in multiple tamped layers provides a sound foundation.

The 4000 Pound Jigsaw Puzzle

Once the base was filled to a level a stone's thickness below the timbers, the puzzle work begins. Here it is best to place the corners and edges and work your way inward. This natural flagstone varied in thickness from 1" or so up to 2" with the bulk of them at about 1 ½". Minor adjustment to the base material was done on an as needed basis. A pry bar and small trowel was used to make these fine adjustments. With the field set with the largest stones smaller ones were then fitted and the whole project fine-tuned with smaller bits. When the entire area was leveled and filled as best as possible some additional crusher fines were added to lock everything in place. Rinsing the stones with the garden hose and sweeping helps lock it all together as well.

With the patio complete the deck stairs can now be planned to provide access from the small deck that is getting replaced.

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