My Rolling Stones Gather Moss. And Algae. And Chipmunk Tunnels.

Our flagstone back patio is a mess, a disaster actually. And we’re in quite a quandary about what to do with it, short of a stick of TNT.

There’s moss and algae in the shady corner by the BBQ and where there’s some run off of water from the house.


More problematic is how so many stones have sunk, the ground underneath it fallen in where chipmunks burrow and where over time, the sand has washed away.

You can see here how this stone has nothing underneath it.

The whole patio is a giant trip hazard, so many stones listing and leaning and up and down.



A few years back we lifted up twenty or so stones and filled the ground underneath with a huge delivery of sand we got. It was backbreaking work but the problem now is much worse that much of the patio has resettled.

Here’s the conundrum: As part of the plan to renovate the upstairs, we were going to create a screened in porch off the back of the breakfast room, bring the propane line under the patio to a place for a gas fireplace. We’d clean and refit all the stones, or maybe even change the entire surface to something else, brick, pavers?

Because we opted out of doing the upstairs work last year, if I were to refit/replace the whole stone patio now, it would be money lost when it comes time that we DO finish the upstairs and screen-in part. Capisce?

So, it leaves us with the cheap way out. Get the stones all cleaned (I’ve seen special scrubbers just for flagstone), then have a dump truck of sand delivered and do the least amount of work to make it right for another year.

Pain in the neck. Anyone cleaned their flagstone deck or have someone do it they recommend? The machine I’ve seen is as large as a floor sander, heavy, too heavy for either one of us to use it.


11 thoughts on “My Rolling Stones Gather Moss. And Algae. And Chipmunk Tunnels.

    1. I’ve read that power-washing flagstone is bad all around. I’m sorry you had to learn it the hard way. It’s like the people who learn that power washing a mossy cedar shingle roof is a bad idea.

  1. Do you really need a machine to clean it? Just washing it with a strong cleaning solution might do wonders. Our slate patio looked to have junk on it like yours. (I used TSP, similar to Soilax® – available at hardware or paint stores – with a little bleach thrown in, and a push-broom with stiff bristles for scrubbing on our slate patio. Did the job and didn’t harm adjacent plantings.)

    For a rehab try your landscaper if you haven’t already. He might be able to do it or know someone who will for a reasonable price. Over the years ours has been the go-to-guy for keeping up the patio.

    1. I’ve done some cleaning with a heavy bristled push brush but what happened is that it left areas clean and others not. I need the entire area done and I think that means a piece of equipment. Everything taken off the patio and then new sand etc.

      I adore my landscaping peeps and have used them for 15 years. They would do this job for sure. Alas, their real quality doesn’t come at a reasonable price.

  2. What is wrong with power Washing? I’ve been spraying my porch (covered, mostly slate/bluestone) for five years. Am I ruining it!?😳 I know you can put grooves in with too high pressure….I spray it a few times a year with a flat, medium pressure.

    Somewhat related, I have an itch to extend our porch into a patio out into the sun. It’s all covered porch, so no sunny spots perse. Any ideas how big a project that might be? The porch is about one foot above grade, one downspout from the gutter goes into the spin and would likely have to be relocated to the other side of the pillar. A couple of sprinkler heads, too. Then, it should probably tie in nicely, and the porch does have a border pattern. I’m thinking 12’x12′ or 15’x15′. Hard to describe without pictures, I know. Plus, there is the greenwich P&Z….likely making the whole idea a pipe dream.

    Have a wonderful weekend!

    1. I wondered the same thing re power washing. We’ve had that done with no obvious ill effects except that it didn’t do as much as scrubbing, as above. EOS – I think the STRONG chemical cleaning sol, ie not Mr Clean® etc, is the key.

      Also my peeps have always used stone dust, never sand. They say the SD is more stable, drifts less, lasts longer than sand.

      1. I stand corrected about the sand versus stone dust. It was stone dust we used. I was speaking generically when I should have been specific.

        The biggest problem on our patio is that when we bought the house there was a GIGANTIC three-trunked tree right outside the kitchen. Hanging over the house, making the patio very dark. Our insurance company told us it must come down as it was a hazard to the rooflines etc. Taking out the trunk and boring down to remove any of the stump left the underneath of the patio compromised in places. It sinks quickly and requires far more dust/sand fill. The chipmunks don’t help it. On one part of the patio closer to the peony beds, when we took up some stones to reset, we were flabbergasted at the little town those critters made. It was a village.

    2. Martha: Perhaps I’m wrong about power washing being bad for the flagstones. It’s something I was told long ago, and assumed it to be true. Most of you here think it’s okay and have done it successfully to prove it.

      Re adding on to your patio, it’s never as inexpensive as you wish. Plus, this time of year, I find no contractor or stone mason wants a smallish job. They want to make hay while the sun shines. The P&Z aspect is the most onerous, here too. I wish I could offer you some advice but I can’t.

      1. Thanks. I wonder if the power washing is an issue with the typical patio construction where stone is laid in the ground with a filler/drainage medium beneath. Maybe it erodes the sand/dust fill, where there isn’t grout? Our porch is attached to the house foundation. I’m sure there are chippies and/or mice under there, but no apparent damage.

        Thanks for the input on patio extending. It will likely be cost prohibitive–hubs will give me a bottle of vitamin d or offer to drag my chaise into the grass. But perhaps I can lobby for 3 months vs 2 in florida😀🌴 (he will not want to pay beaucoup $$$ to easily move our outdoor table into the sun on six sunny but cool in the shade spring days per annum)

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