Raised beds with large vertical slate / flagstone slabs - has anyone done this?

Hey everyone!

This coming year we are going to retrofit our backyard to remove all grass and turn it into a series of winding garden paths using stones that are readily available in our area (Bulgaria). They look like this: https://valmargstone.com/en/%D0%BF%D0%BE%D0%BB%D0%B8%D0%B3%D0%BE%D0%BD%D0%B0%D0%BB%D0%BD%D0%B8-%D0%BF%D0%BB%D0%BE%D1%87%D0%B8-%D0%B3%D0%BD%D0%B0%D0%B9%D1%81/%D0%BF%D0%BE%D0%BB%D0%B8%D0%B3%D0%BE%D0%BD%D0%B0%D0%BB%D0%BD%D0%B8-%D0%BF%D0%BB%D0%BE%D1%87%D0%B8-%D0%BA%D0%B0%D0%BC%D1%8A%D0%BA-%D0%B3%D0%BD%D0%B0%D0%B9%D1%81-%D0%B7%D0%B0-%D0%BD%D0%B0%D1%81%D1%82/

For the paths, I plan on simply laying them on a weed-suppressing fabric and adding light soil around them implanted with creeping thyme seeds which will eventually fill in the cracks - similar in a way to the photo in the link where they have moss growing in between. I think that part will work out just fine.

The part that I am less sure of, is using these same stones dug vertically into the ground, and staggered with a back-and-forth overlap, similar to what you see here... but with a much more uniform height: https://www.hgtv.com/profiles/professionals/sun-valley-landscaping/photos

Soil will be raised up in the areas contained within these natural stone slabs. I don't think I'll need to put any mortar to hold them in place, so long as the slabs are flat and have enough of an overlap.

But my question is this: I can't find an example of anyone doing this with these larger slabs in a vertical orientation. That might mean there is something incorrect about the idea, or maybe it's just an expensive option in many areas. They may bend out over time, which could be corrected or fastened with concrete underground (I don't want to do this for a number of reasons).

Anyone have experience doing something like this?

An interesting plan for sure!

I think a big factor is already what you guessed, cost.

I live in the Northeastern United States in 'slate' country. My village sidewalks actually used to be large slabs of slate that I would walk going from my home to school and back every day! A consideration to keep in mind is that slate can become VERY slippery when wet. I've taken a few tumbles in my youth.

When it comes to the vertical orientation, I can't say that I have seen it before but I would imagine it would require balancing how deep you place the rock compared to how stable it is standing on its own. I wonder if just compacting the soil after you installed them would suffice?

Thanks for the response!

Yes, if the stone isn't readily available in your area the cost can be high. There is a supplier that can deliver pallets of the stuff about 25 minutes away, and the cost of natural building materials in Bulgaria is a lot lower than when I lived in Canada.

The idea would be about a 40% submersion, with whatever the pointiest tip inserted the deepest into the ground.

Before we begin this project we'll be running lines for automatic irrigation, I'll just need to remember where those lines are when digging the holes from the slate.

From your first link:


How beautiful! I would call this form of paving 'crazy paving' It used to used a lot in Britain after WW2 (probably using rubble from the war!) I've seen garden walls clad with it in Birmingham UK too. It sounds from the link that the stones are gniess, which I believe to be a form of granite - very pretty.
I do have some experience to contribute - not using angled slabs, but large concrete paving slabs. I made a retaining wall for my garden in Solihull to level the lawn out to the boundary fence to make it easier to mow - actually planted a mixed hedge in the infill area. It worked perfectly for fifteen years or so before we moved up here. Since the slabs were regular rectangles in shape it wasn't so complicated getting a wall, and I just butted them up together. I may have some photos somewhere, I'll see if I can find them.

I personally would never use plastic weed membrane barrier again, having had problems removing it from around my trees. I guess it depends on whether trees are likely to seed themselves in your pathway.

Nancy Reading wrote:
I personally would never use plastic weed membrane barrier again, having had problems removing it from around my trees. I guess it depends on whether trees are likely to seed themselves in your pathway.

This is the stuff we've used before in our greenhouse and it works really well for us: https://www.amazon.de/Professional-Water-Permeable-Tear-Resistant-Environmentally-Resistance/dp/B0B9P219MY/ - tear resistant but water permeable.

And yes, the stones are very beautiful and available in a number of colours. we bought some smaller dark grey ones to clad our fireplace stovepipe, and medium-sized beige ones for the floor of our outdoor kitchen:



(It's the garden space in behind the kitchen that is about to get transformed)

Oh, how wonderful! The paving idea is stunning, and your that outdoor kitchen is superb! If the vertical slabs for the edging are buried 40% into the ground and well compacted I imagine they should be stable, unless you're on very loose sandy soil that won't compact.

I intend to set an outdoor kitchen up at my house in Bulgaria, too, though it won't be nearly as lovely. I want to do crazy paving paths, and will try the old lino from the floors -- proper old-fashioned lino on hessian backing, not vinyl flooring -- as weed control mat beneath the paving. It will crack and biodegrade over time but hopefully by then the paths will be well enough established that it won't be an issue.

If only I'd discovered this place 20 years ago. So many plans, so slow getting anything done! I'll need to live to 120 to do all I want there!

I have used curvy terra-cotta roofing tiles  with some success. After a few years, they worked their way lower into the soil. Pretty idea!

Lee Valley tools in Canada sells connectors for prefab concrete pavers. I have never used them: I just build compost hills, but I am posting the link in case this is helpful. They do sell online, but I expect other places in the states do as well:

https://www.leevalley.com/en-ca/shop/garden/planting/pots-planters-and-baskets/beds/47455-raised-bed-kit

I would agree with Jane about burying them at least 40% and tamp firmly. They will move with the changing seasons

It depends on whether you plan to have grass or creepers that you need to keep out of the beds. Overlapped stone will not prevent grass or creepers from infiltrating. Probably fine with mortar our a non biodegradable liner though. It'll look great.

Don Komarechka wrote:
But my question is this: I can't find an example of anyone doing this with these larger slabs in a vertical orientation. That might mean there is something incorrect about the idea, or maybe it's just an expensive option in many areas. They may bend out over time, which could be corrected or fastened with concrete underground (I don't want to do this for a number of reasons).

Such slabs will definitely lean out, starting when the bed is filled and continuing until they're flat on the ground. It's due to the simple physics of having unbalanced force. It might look nice at first, but your hard work will be in vain unless you drive in so many posts that it won't look the same.

Peter White wrote:It depends on whether you plan to have grass or creepers that you need to keep out of the beds. Overlapped stone will not prevent grass or creepers from infiltrating. Probably fine with mortar our a non biodegradable liner though. It'll look great.

No plan for grass, but between the pathway stones will be planted creeping thyme.

The stones have been ordered, by the way! Delivery tomorrow. They were an extra large and relatively thin grey variant, thick enough for strength but easier to handle. I will do a test garden bed at the front of the house while still planning the irrigation for the back.

If you are placing the large slaps vertical, start with sloping them in about five (5) degrees inwards.  That way, you will have a fulcrum effect.  With the effect of gravity, the blocks will tend to push out from the bottom.  and compress the back fill outside of the  bed.

Peter White wrote:It depends on whether you plan to have grass or creepers that you need to keep out of the beds. Overlapped stone will not prevent grass or creepers from infiltrating. Probably fine with mortar our a non biodegradable liner though. It'll look great.

I have 96 of these, in various arrangements, any that have a crack or two, even in just the length of your hand, eventually will have your bed material working its way out.  So I would use some of the "material mentioned" to line the inside of your possible pavers.  I bet they will look great.

I will say, I have to water near twice as much as if this was all in the ground.  But that being said, raised beds or containers are super enjoyable. And after 10 years or so, I would never go back.  Nothing better than working in the garden after a 2" rain, (same day) and not get muddy feet.

By the way, Peter, in my opinion is very correct, it might take a few years, but things outside of the bed, will want to get inside your beds. The cracks really help the things get it.

Best of success.

Paul Fookes wrote:If you are placing the large slaps vertical, start with sloping them in about five (5) degrees inwards.  That way, you will have a fulcrum effect.  With the effect of gravity, the blocks will tend to push out from the bottom.  and compress the back fill outside of the  bed.

Excellent advise, thanks very much!

Scott Weinberg wrote:By the way, Peter, in my opinion is very correct, it might take a few years, but things outside of the bed, will want to get inside your beds. The cracks really help the things get it.

Best of success.

I have no doubt that there will be unwanted elements getting into the beds, probably within months of building them from airborne seeds. We live in a rural village and there are abandoned properties all around us that are no doubt full of weeds and invasive plants. We've come to accept this and fully understand that reactionary weed-plucking will be a part of the process moving forward. Thanks for your other comments as well - we grow a number of trees in pots and are considering peppers this year, such that we can overwinter them inside for a second year and greater productivity on more mature plants.

Delivery received!

Wow, looks excellent for your project.

Beautiful stone
I have done what you are planning on a small scale. As long as you follow previous advice on burial and back-sloping you should be fine. Any grass will definitely migrate through the overlaps, but at least it will give a weak point for pulling roots. I tend to add bulky rocks buried at ground level outside of the vertical slabs to give a bit more resistance to tilting, and also to make it easier to mow grass at the edge as there are few tufts coming up right next to the slab where they are hard to cut.

Update: First bed.





This concept will work. The process was a bit tricky as I wanted to displace as little earth as possible, but the narrow tools and the edge-cutting tools were not robust enough and started to bend. During this process I discovered the company "Root Slayer" which makes a weeding tool 10cm across with the ability to force it into the ground with my feet. Extremely resilient and effective, once the grass is cut - the cutter I have is not good enough, but one from Root Slayer is on order to cut out the rest of the trenches. Stone seems stable. Will look much better when the whole yard is done. A lot of work still to do.

We had to cut down a cherry tree that didn't survive last year's dry heat, so some of the wood from that is buried in the bed under the soil. Some beds will be shallower based on the stone size, but I think there will be enough to complete this project. More to come as this project progresses.

Ohh how neat, thank you for the update!

I was wondering a few days ago how this was going. It is one of those things that is done slow and steady but the finished product is something that is envy inducing.

Update! Getting there. It's really coming together nicely, but a heck of a lot of work:

That's looking great Don. You can really see it coming together.

I'm wondering whether the reflective nature of the stones give opportunities for some really hot microclimates? That could be a good or a bad thing depending on your climate. I'm not sure how hot/cold your weather gets, but something to consider perhaps.

Nancy Reading wrote:That's looking great Don. You can really see it coming together.

I'm wondering whether the reflective nature of the stones give opportunities for some really hot microclimates? That could be a good or a bad thing depending on your climate. I'm not sure how hot/cold your weather gets, but something to consider perhaps.

Thanks! Two more beds and some of the stone have been placed around, and a herb spiral from old bricks is halfway constructed beyond what you see in these photos. Updated photos to come soon.

For the micro-climate, you may be right that the stone will increase the heat absorption. That can be a good thing as many of the plants can survive in higher USDA hardiness zones, though some are sensitive to too much heat; one of the beds is filled with haskap berry bushes, and I have some netting to cover it during the summer months as a bit of reprieve from the heat.

I am surprised how quickly the clay soil drains in the beds (everything around here is clay-ish). With the irrigation system in place, it's easy to add water and good to know that I won't have to deal with rotting roots - though it's important to monitor things. I've just purchased a soil moisture sensor that will make that task easier.

What a creative idea! They look fantastic, artsy, and functional! You could always add in a dry stack seat using the same technique Tim did in his dry stack moon gate. Or, maybe a bench?

Tina Wolf wrote:What a creative idea! They look fantastic, artsy, and functional! You could always add in a dry stack seat using the same technique Tim did in his dry stack moon gate. Or, maybe a bench?

Thanks! Here's the updated progress. Nearly there. A few rainy days have slowed me down.



I have one giant piece of stone I'd like to make into a table, I know that much. Will see what's left over from this load of stone. The yard I bought it from has some super thick stuff that would work better for benches - might need to pay them another visit.

And, if we are able to buy one of the neighbouring abandoned properties, we fully intend to install a moongate as the accessway.

Stunning! Such a beautiful space!

OMG!   Thank you so much for your post.  That is what I'm planning to do (on a MUCH smaller scale) for a raised iris bed.  I had no idea if it would work.  The info and pics were so helpful. I'm using leftover stone that was used to frame my sliding glass doors.

You're welcome!

The project still is not complete as we immediately switched to +30C weather and the final round of plants couldn't be shipped and heavy manual labour moving stones/soil in the heat isn't a fantastic idea either. Will resume in the fall, but I can report that the plants are loving it.

One bit of advice I'd give you is cut the trench as narrowly as possible. Really helps the stones stay vertical against the undisturbed compacted soil around them.