Devine Escapes
hardscape contractor in Blakeslee PA
devin@devineescapes.com

Do you use landscape fabric under stone patios?

Here’s a common question about how to build a stone patio, that I haven’t addressed in any of my DIY articles yet–do you need fabric under your flagstone pavers? Actually, it’s a series of questions:

• should you put fabric underneath your flagstone pavers?
• if so, where do you put it/how do you install the fabric?
• will putting landscape fabric beneath your flagstone stop weeds?
• what type of landscape fabric should you use beneath your flagstones?
• Do you use landscape fabric in gardens or lawns to stop weeds?

Quick answer: no, landscape fabric will not prevent weeds in your stone patio–but there may be other reasons to consider using landscape fabric beneath your stone patio. Usually, you’re fine without it, except for some special cases. Read on! The above bullet points are each answered in turn, below.

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landscape fabric under stone patios– and weeds

landscape fabric will not stop weeds, ever, do not ever use it for that purpose

There’s at least one international concrete paver institute out there, who offers a 2-day certification course and teaches everyone that we should lay a geo-textile fabric underneath our gravel, when installing hardscape paver units. Back when I took such a course they were recommending that contractors use, more specifically a “woven, geotextile fabric” on top of compacted sub-grade/underneath the gravel that is to be compacted.

Now I took that test eighteen years ago, back when concrete pavers ruled the world and hardly anyone even remembered what flagstone, or natural stone of any type, even was. In 2007 I started my own business, Devine Escapes, specializing in natural stone and eschewing all concrete pavers, stamped concrete, fake veneer, and all other faux stone products. Let’s just keep it real, okay? As the years have gone by, the public has likewise had a bit of a backlash against all the faux, fake, ersatz and pseudo hardscape products out there–more and more homeowners have been asking your hardscape contractors for real stone. Like back in the olden times! But with modern sensibility, right….like 10 years after I started leading this charge, now I see people calling it “rustic chic”.

Related content: No plastic in the landscape

I used to call it, “natural materials, built to traditional standards, with an eye for artistic form and fine detail”. (old slogan of mine).

But you see, all these guys who learned how to do concrete pavers, and have only recently begun doing natural stone, they are all just using the same methods as they used for pavers….and applying it to stone. There are similarities to concrete paver installation and flagstone installation–but there’s important differences too.

Related content: how to install dry laid flagstone

should you put landscape fabric under stone patios? In most cases, the answer is “no”

But on those occasions when you will want to use fabric, this is the stuff you want.

I used to use fabric, always, on every single flagstone installation (whereas these days, I use geotextile fabric underneath maybe half of my stone patios) And I used to use fabric and gravel behind my dry stone walls….after learning that pouring gravel behind a dry stone wall and then covering it with fabric might not be the best idea (it’s really not) then I began to question the need for fabric beneath my flagstone as well.

Of course the thing about preventing weeds has already been debunked. Aside from that, there are two structural justifications for using fabric beneath your gravel foundations:

• use landscape fabric/geotextile fabric to stabilize the soil
• prevent transmigration of soils

Stabilize the soil

Okay, so you dig down 7 to 10 inches (depending). Compact the sub-soil, which is usually clay. Lay fabric. Then lay gravel, then tamp that gravel. Then set your flagstones out–first the puzzle, then once all the flagstone’s been puzzled out, you level them up one stone at a time upon a bed of stone dust (screenings, decomposed granite, 8th inch minus, quarry fines–stone dust goes by many names, depending on your location).

The subsoil may shift slightly, over the years, sinking and or heaving. You don’t want that–that’s why you dig down and compact the soil–making sure there’s no roots or other organic matter down there, and then compact the gravel. Both the clay and the gravel can and will move, slightly. So will concrete mind you–just when the concrete moves, it cracks. So stabilizing the soil here means that the weight is spread out. the fabric is all spread out….picture a 100 pound object set atop clay soil. The object might only be 1 foot wide. It may sink, over time on that clay soil, right? Well, what if you lay a  piece of plywood out on that soil, then put your hundred pound statue of liberty reproduction, or garden gnome, or whatever down on top of that plywood. Less likely to sink, right?

That’s what the fabric does. The weight is spread out. In fact, I’ve seen so many patios that did NOT have fabric beneath them, yet 10 years later they still look great. I’ve seen other flagstone patios that DO have fabric beneath them–and seen them need maintenance. Look, I’ve been doing this for some time now and from what I’ve seen so far, I can not state that the addition of fabric will make any real difference as to whether or not the flagstone patio will need maintenance down the road.

Compact the sub soil, pitch everything right, compact your gravel, use enough gravel for the particular site, use appropriate sized flagstones, just overall know what your doing and try your best–and the flagstone will still sit nice and level years and years later. You might need to re-level a couple of stones, slightly over the years. In my experience, that is rare, rare, rare. I’ll check in with clients from years ago and they tell me, “nope! no maintenance needed!”

Where do you put it/how do you install landscape fabric under stone patios?

Between the soil and the gravel.

In addition to (theoretically) spreading out the weight and thereby minimizing the movement of soils, using the fabric also allegedly stops “transmigration of soils”.

Okay, I’m a bit skeptical of the second part. Transmigration of soils is supposed to be little bits of stone dust and gravel sinking down from your gravel bed and into the clay. Nope–I’m not buying it. Soil is compacted, gravel is compacted–any so called (let’s try and say this with a straight face, not a sour incredulous grimace) “transmigration of soils” is going to be so minimal as to be far beneath our notice or concern.

will putting landscape fabric under stone patios stop weeds?

Well, think about it. Your flagstone is what, inch and a half or two inches thick, with stone dust in the joint…..Then you’ve got what, an inch of stone dust underneath your flagstone and then 4 to 6 inches of compacted gravel. Any weed whose root makes it that far down, all the way down to your fabric–any weed like that is going to laugh at your geotextile fabric. Think tap-root. Think dandelion.

Even if the root can’t bust through the fabric, it still is embedded in 8 inches or so of gravel. It’s in there already!

So the answer is a resounding NO, landscape fabric will not stop weeds in your patio, walkway, flagstone nor pavers.

Okay, but why not put the fabric on top of the gravel, underneath your stone dust?

Okay, first off, you just can’t put the fabric right under the stone–the stone will rip it. So maybe underneath the stone dust?

Problem there is that first you have to puzzle out your flagstones–so you’d have to lay out your gravel, compact that, then lay out fabric–then puzzle out all them stones–right on top of the fabric. You’ll rip it all up.

Even if you could put the fabric inbetween the gravel and stone dust–your weed roots would still have to make it past an inch and a half of stone dust filled flagstone joint, plus through an inch or so of stone dust leveling bed–so that weed would be a) able to live on stone dust, with no actual topsoil or clay soil in sight or b) won’t mind busting through that fabric.

Bonus: how to cut flagstone using just a hammer:

landscape fabric under stone patios–what type of fabric should you use?

Filter fabric. Non-woven geotextile filter fabric. Just call your local hardscape supplier and ask for “the felt stuff”. It looks and feels like felt–and it allows water to pass through. Some woven fabrics, plastic landscape fabrics won’t let water pass through very easily, some fabrics sold as weed fabric will do the same. Go with felt–IF you choose to use fabric.

landscape fabric and spongey clay soil

So here’s one use for fabric–say you go to build a hardscape, you dig down, then you go to tamp–and the clay soil does not tamp properly, becomes spongy feeling. Step down, and it’s  like walking on a water bed. You don’t want to build on that kind of base. But  it’s time to lay gravel and get it down, right?

In that circumstance, the more you tamp, the more water from below gets brought up. It just gets spongier. So you can wait for the sun to dry it out–might take days. Hopefully it doesn’t rain while you’re waiting! Or dig down deeper and just use more gravel? Might work…if you go a lot deeper and use a lot more gravel.

Here’s how you do it:

using landscape fabric to stabilize spongy subsoil

1. Dig down a bit deeper. If you were going to have 6 inches of gravel, make it more like 10.
2.  LIGHTLY compact the subsoil, using a hand tamper not a plate compactor and certainly not a jumping jack. If soil is sticky clay, add just a bit of gravel to that soil before tamping–now your tamper won’t get covered in heavy clay. That’s another pro tip for you and you are welcome.
3. Lay out your non-woven geotextile felt-type fabric.
4. Spread out a few inches of gravel.
5. Lightly hand-tamp.
6. Put down another layer of fabric, lightly tamp again. At each lift, the camp acted base should become less and less spongey.
7. Another few inches of gravel, then fabric, then tamp–repeating until you bring it up to the right height. Now step there again and guess what? It feels solid underfoot–no more waterbed effect.
8. How much does the fabric actually help? I’m not sure! Maybe it’s more about the few-inch-lifts of gravel and the light tamping. I DO know however that this technique holds up, over years. Having encountered spongey subsoil on many many properties, AMD then used this technique to deal with the situation–visiting the same properties ten years later and they have held up quite well.

Essential tools needed for flagstone installation:

• https://amzn.to/3AxXV4i wood handled brick hammer. Happens to cost less than steel….but I prefer wood, less jarring on the elbow.
• https://amzn.to/3tXYMsR Dead blow mallet.
• https://amzn.to/3ksajx9 Angle grinder. Same one I use.
• https://amzn.to/2VYb8Ey Blades.
• https://amzn.to/3hU8hoa Brick chisel.
• https://amzn.to/3ktol1G Grabo. Not cheap, but it will save your finger tips from having to pry up heavy stones. Worth it, if you plan on laying more than 200 square feet (or so) of flagstone.
• A couple of 5 gallon buckets (for stone dust, when leveling stones)….shovel, wheel barrow…..4′ level
• https://amzn.to/3hWi0tR Pick maddock. Best way to dig. Break up soil with this, then use shovel.
• https://amzn.to/3lFjfPi Knee pads–essential.

So when should you use landscape fabric under stone patios? When should you not use it?

Well if in doubt use it, it can’t hurt, right? It does cost money and all things we produce do have an environmental impact AND professional opinion states that most flagstone patios will be fine without the fabric–and at most, my usage of such fabric has maybe saved a few of my clients a small, small amount of maintenance. So maybe I didn’t have to return to re-level 2 stones on a thousand square foot patio. Heck, that fabric costs about the same as the bill for such a small bit of maintenance would cost. They’re both nominal expenses.

1. If you know the soil is stable–if the soil has not been disturbed in 10 years, it’s probably stable. If an old patio sat there for years…..probably stable. No need for fabric.
2. If the area is prone to flooding…might not be stable. Use fabric. If the house was just built a few years ago, that soil might not be stable, again– you might want to use fabric.

What we can reasonably assume, from the spongy soil example above, is that the fabric actually CAN stabilize soils which are prone to movement. As such, if you’re working on recently disturbed soils, from new construction, or in a place that may flood–then you pribably want to dig deeper, use more gravel, and/or use a bit of filter fabric.

On the eco-tip

True, both the gravel production and fabric production do involve some environmental impact. Then again….if you build a poor flagstone patio and it needs to be re-built–that will have even more negative impact. Let’s take our time and build beautiful structures that last and last.

related articles:

• DIY consultation services (one on one time with a professional hardscape contractor)
• polymeric sand between flagstone pavers? (spoiler–it’s a bad idea)
• vacuum lifter for lifting stone slabs
• how to build dry stone walls (nope, they do not need fabric behind them either)