The Patio Project
When my wife and I had our current house built in 1994 we decided that the back yard was way too small to bother trying to do anything with it in terms of landscaping and a lawn. We contracted with a local gentleman to build a flagstone patio instead with xeriscaping around the outside of the patio. This approach seemed to make the best use of the space, required little maintenance and was environmentally friendly since the xeriscaping required very little water. We especially liked the idea that a flagstone patio wouldn't require the regular power washing and staining required of a real wood deck (fake wood products were only just becoming available at that time and we didn't like the appearance of the products available).
Fast forward a few years and the neighbors uphill from us had a severe water leak (contractor's fault). The area of Colorado we live in has what is known as “expansive soil” that expands like an old sponge when it gets wet and expand it did. Besides causing a few within spec problems inside the house, the expansive soil caused the patio to heave up several inches as compared to its original height as compared to the house.
We're still not sure if the expansion we saw was due to our neighbor's water leak but we haven't seen anything like it in the years since. In fact, as the soil has returned to its natural moisture level the soil under the patio has shriveled like a dried out old sponge and the patio has, for the most part, returned to its original level. Unfortunately, this settling has not been uniform and resulted in a rather large crack appearing in the patio with the portion of the patio on the house side of the crack settling a couple of inches more than the side of the patio on the outside of the crack. This is probably due to greater subsidence from the wet/dry cycle in the contractor's backfill close to the house.
This left us with a safety problem since the displacement between the two sides of the patio was a good couple of inches. In addition, the crack was pretty unsightly so I decided to do something about it.
The first step was to rip up the old flagstone patio at least where it had subsided. Luckily, quite a bit of the patio had crumbled so at least some of the going wasn't too difficult. In other areas the patio had subsided but the flagstone still had fairly good structural integrity which meant breaking it up was a lot of work.
Also, since the goal was to be able to reuse the flagstone (pain to dispose of the old and a lot of work and additional expense to bring in new) there was a rather large pile of debris.
After a valiant struggle (that required a fair quantity of beer to keep me going), the area of the patio most affected by the subsidence was cleared. It was also at the point where the remaining patio was in fairly good shape so breaking more of it up 1) didn't make sense and 2) would have been an awful lot of work.
Rather than rebuild the patio as it had been done originally (flagstone over mortar over rock and sand fill) I decided to go with a scheme that would be a little more forgiving to possible future soil movements. My plan was to use the old mortar “underlayment” as a foundation, use sand to level and provide stability, place the recovered flagstones on the sand and then use some sort of loose fill material be tween the flagstones.
The first step was to provide a way to keep the broken mortar, sand and loose fill where I wanted it. This required building a small retaining wall using pressure treated lumber. The design I came up with has the retaining wall “free floating” with the patio material holding it in place against the house's foundation.
The next step was somewhat unexpected but, in hindsight, not all that surprising. The original patio was really a rock retaining wall with the interior area filled and then capped with the flagstone. Given all of the movement of the patio surface, it isn't a surprise that the retaining wall had suffered some structural problems too. This meant I also had to knock down and rebuild the retaining wall where it has also cracked.
The repair portion of the wall shows up as having a different color of mortar (light gray) as compared to the original mortar (dark gray-brown).
Once “the wall” was repaired I got to spend my time “making big rocks into little rocks” (to quote the old hard labor sentence) to clean the old mortar off of the old flagstones. The result of this effort is visible both in the picture of the wall repairs (above) and below. My goal was to break the old flagstone into small rubble with individual stones no more than about 1.5 inch in diameter.
As you can also see by the above picture, the time of year was now late fall of 2007 and I decided the construction season had come to an end. I replaced the flagstones piled around the hole in the above picture to create some semblance of what the patio was supposed to be like and promised my wife that I would pick the project up in the spring. Life threw a monkey wrench into my plans when in early spring of 1008 I found out that my oldest brother, Rob, was extremely ill. Rob died of cancer in May of 2008.
After helping get my brother's estate in order it was back to work on the patio. After clearing the flagstones from the rubble bed, I rented a plate compactor and ran it over the rubble for several hours. The result was almost like I had paved the area.
The next step was to create a bed of sand which would provide a means of both leveling the flagstones and a stable bed. The next picture shows the rebuild after my wife and I hand carried about half a ton of sand from the front of our house to the patio in back.
At this point we were getting close. The next step was to solve the jigsaw puzzel of where to put the flagstones. Luckily, I'm pretty good at spatial problems so the result was pretty good.
Based on the recommendation of the folks at our local landscaping suppy place, we decided to use a product called “Envirostone” to fill in between the flagstones. This is kind of an enhanced form of unwashed gravel that includes a weed killer and an adhesive. We're pretty happy with the result.
In fact, we like it well enough that I'll probably take on doing the next worst looking area of the patio next summer. Luckily, it's only about ten square feet while the above was about one hundred square feet.