Posts Tagged ‘flagstone’
The corollary to the East Coast Connecticut Blue, is our West Coast Arizona flagstone. It’s sort of the ubiquitous, default flagstone of Bay Area gardens, but I’m always happy to use it. It’s easy to work with, and I like the color range, with each of the colors having a slightly different feel. Oak is the hardest; Buckskin and Peach are the nicest to work with; Sedona Red is the lowest quality, the one to avoid.
Peach is probably my favorite, though in the Bay Area it tends to gray over time if it doesn’t get a lot of sunlight and air circulation or if you don’t put a sealer on it. I showed the photo of this patio once before, but here are a couple of more photos. The plants have really filled in around it.
The Pacific Wax Myrtles are eight feet tall now, three years after planting as five gallons. I think they’re going to lose the race with the workers constructing the McMansion next door, but they should provide a good screen fairly soon.
Last month I went back and built a second patio with the leftover stone and another new pallet of stone. The cinder blocks are new veggie and flower beds that the clients are building. I think the block will eventually get mortared and stucco’ed.
Sedona Red is by the far the softest, weakest, crumbliest of the Arizona flagstones. My parents house was the only place I’ve ever used it, and I hope to never use it again. Fortunately, the patio is mostly to be seen and is rarely walked on, so there haven’t been problems with cracking. This is a photo of it in its first year; I had some nice photos of it this spring with a ton of crocuses blooming, but those photos were lost when our laptop got stolen. If the crocuses do their thing again next spring, I’ll swap this photo out for a better one.
You don’t really want sandstone to be this striated; it’s often a sign of how weekly bonded the layers are. With other Arizona sandstones, the striations are not nearly as distinct.
The topic for this month’s design workshop at Gardening Gone Wild is dealing with slopes. The description mentions “tips for building steps and paths to make slopes easier to navigate,” so I thought I’d cite the source I learned from, the forest service Trail Construction and Maintenance Notebook, which is online and in the public domain (Who owns this government document? We do!). The text might have a few elements geared towards public trails rather than residential gardens, but the diagrams are good and the principles are solid.
‘Build stairways from the bottom up, at a break in the grade. The most common mistake is to start part way up a grade. If you do so, the trail will wash out below the stairs. The bottom stair should be constructed on a solid, excavated footing. If it is constructed on top of exposed rock, it should be well pinned to the footing. Each successive stair is placed atop [or against] the previous stair. Dry masonry rock stairs usually rely on the contact with the stair below and with the footing to provide stability.
‘Hikers, especially backpackers, generally don’t like steps and will walk alongside them if there is any opportunity. The steps need to be comfortable to climb or they won’t be used. This means keeping the rise a reasonable 6 to 8 in (150 to 200 mm) and the run long enough to hold a hiker’s entire foot rather than just their toe. It’s helpful to armor the sides of steps with rocks to encourage users to stay on the steps.’
‘The most important area of the step is usually in the run. This is where most traffic steps as it climbs. If the step is composed of something like a board on edge with fill behind it, then the traffic will step onto the landing. Almost all foot traffic descending the step will walk off the edge of the step. The top of the step (and landing) should be stable and provide secure footing. The edge of the step should be solid and durable. The face of each step should not contain a batter that creates a “face run” of over 2 in (50 mm) from top to bottom. This is particularly important as the rise of the step increases.
‘Steps with landings are a bit harder to secure in place because the stairs do not overlap. Each step can either be placed in an excavated footing and the material below the rise removed to form the landing of the next lower step. This is usually the most stable arrangement. Or the step can be secured on the surface and fill used to form a landing behind it. The material used to provide the rise does double duty as a retaining structure when the landing consists of tamped fill. These steps must be seated well to prevent them from being dislodged by traffic. For stock use, landings should be long enough to hold all four of the animal’s feet.’
‘In more primitive settings, you don’t need a uniform flight of steps as long as the route is obvious and there is solid tread at each stepping point. In the Sierra, a cross between cobblestones and stairs, locally called riprap, is commonly used for this purpose.
‘If the stairway climbs straight up the hill, each step should be slightly crowned to drain water to the edges or slightly sloped to one side. When the trail traverses a slope, each step and landing should be slightly outsloped. Water should not be allowed to descend long lengths of a set of steps or to collect on or behind a step on the landing. A drain dip where the trail approaches the top of the steps is a good idea.
‘In all steps, the key is to use the largest material possible and to seat it as deeply as possible. Rocks should be massive and rectangular. On steps that traverse a slope, it helps to seat the upper end of the step material in footings excavated into the slope.’
Best practice for building a stairway these days, if the rocks are big enough, is to butt them against each other instead of on top of each other. That way it is possible to repair one of the steps without redoing the whole staircase.
It doesn’t say in the notebook, but I was taught to kick test every step. If the stone moves when you kick it, it isn’t solid enough. A bit of a shock, sometimes, to see someone kick the structure you just labored on, but the step is definitely going to get kicked when people use it, so you might as well find out if it is going to last. You want to feel confident that your stairs are safe. It’s scary enough the first time you see a mule train crank through a set of steps that you’ve built even when you know the steps are solid. There aren’t mules in residential backyards, but the foot of a 150 lb. person can easily impact with 300 lbs. of force, so the basic principle is the same. Steps should be strong.
Steps also need to be regular. The test is to walk up and down the stairway without looking down at your feet. If the rise and run are even, you shouldn’t trip or stumble.
In the front country I usually don’t get to work with stones that are “massive and rectangular,” but I still kick test every step and walk the staircase with my eyes closed. This set of steps, built with a local sandstone called Old Town Wall, was a lot of work, getting the risers to all match and the stones all interlocked enough to stay in place. I was working for a designer who is a serious dry stone purist, so mortar was out of the question. I think the steps and cheekwall took me longer than the entire rest of the wall.
When it’s up to me — though I’m a dry stacker at heart — I usually build steps with mortar, usually by stacking flagstone with a recessed mortar joint. I don’t think that method holds up in areas with heavy freezes and probably not if the steps are going to be used by mules, but it does well in Bay Area yards. A before photo of these steps and another mule photo are below. (more…)
Here’s another hellstrip walkway, from our own hellstrip in front of our house. It has a piece of Champagne in it, but otherwise is not much like the other. I’ve been adding to it for a while, building it with leftover stones from various jobs. There are seven different types of stone, though two of them, the Cabernet and the Sonora Gold, are so small they mostly just pad the total; the box for the water main should almost count as number eight. The Connecticut Lilac in the lower right was the first. It’s 3″ thick and really heavy, so I didn’t want to have to load it up to haul to another site. The most recent stones are in the upper left, Three Rivers, from a recent path installation. The only stone type I rejected was Sedona Red, a brick colored stone that looked awful; otherwise, if it was flat and the client didn’t want the leftover pieces, I stuck a few in the hellstrip. One of our ideas in starting this blog was to accumulate examples of different kinds of stone and stonework, but I’m not sure what this is an example of, other than what can happen when a stoneworker decides to make a crazy quilt. The list of stone types:Three Rivers Connecticut Lilac Arizona Peach Arizona Red Champagne Cabernet Sonora Gold
One of our clients calls Three Rivers flagstone “purple zebra,” which is a pretty accurate description. It always catches our clients’ eyes when they visit the stoneyard, though they often balk at the price, as it became really expensive a few years ago and is probably the most expensive flagstone commonly available in the Bay Area. It’s from one of the largest flagstone quarries in the United States, located up in the Sawtooth Mountains in Idaho. The quarry wanted to expand and the Bush administration, in their inimitable way, told them to go right ahead and not worry about doing an environmental impact study. An environmental group, the Western Watersheds Project, which owned a wildlife preserve adjacent to the quarry, then sued, and a judge agreed with the environmentalists that yes, U.S. law does require environmental impact studies, and temporarily shut down work at the quarry. Everyone settled out of court and the price then went up a couple of hundred dollars to around $750/ton.
I’ve seen the stone described as a type of quartz-sandstone and as argillite. Answers.com defines argillite as “an intermediate between shale and slate, that does not possess true slaty cleavage,” which sounds about right, except that I would add that Three Rivers is really hard and heavy. (Can I say that I prefer my stone with a bit more cleavage? It’s true. Cleavage is the tendency of stone to break cleanly.) The swirls of color in Three Rivers come from irregular mineral layers which look cool but make the stone inclined to break irregularly. The patio in the photo, for instance, has rougher, wider joints than I would do with a cleaner-breaking stone like a sandstone. To get tight joints with Three Rivers, you pretty much have to cut everything with a saw. We usually only use Three Rivers for stepping stones, paths, and small patios; it can look too busy when used for larger areas.
Quarriesandbeyond.org has links to info about the Three Rivers quarry on their list of quarries in Idaho.