Flagstone patio--mortared vs. gravel/sand?????

colbyj(No. CA)July 19, 2003

We need some advice on laying a flagstone patio...

We originally planned to lay the patio on a gravel and sand bed with the joints filled with sand. However, the guy doing the landscape design said we need to mortar the patio if we plan to use it for entertainment purposes, such as having a table and chairs on it. He states that if we do not mortar it we will chip the edges of our flagstones and it will eventually need to be redone.

We are located in the northern California foothills, where the weather varies from mild winters to hot summers, with occasional freezes in the winter months.

Any recommendations would be greatly appreciated.

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He's wrong, unless by "eventually" he means in a couple of hundred years. If it is laid in a properly prepared sand bed, and it's thick enough (1.5 to 2 inches thick is the standard for patio stones that are not going onto cement slabs), and it's average quality sandstone ... it will last as long or longer than mortared. I've been running fully loaded hand trucks across my sandstone atrium and even ran over one with the truck and nothing happened. I've seen loose-laid sandstone slab patios around here dating from the 1920s. You have to top up the gravel between the stones occasionally, that's all.

Worst case is you have an earthquake and have to lift and relay a few stones in the sand to flatten them. With flagstone mortared to a concrete slab you would have to replace the slab and the rocks if it cracked.

If he proposed laying it on a sand bed and then mortaring between the joints, or laying it in a thick but unreinforced mortar bed on a sand base, RUN! There will be enough shifting that the mortar will crumble in a couple of years. It either has to be free to move (stone on sand) or solidly held down by mortaring it onto a reinforced, cured concrete slab. The sandstone has to be soaked at least overnight in water before mortaring or it makes a crapo weak installation.

Here is a link that might be useful: Sandstone slab on dirt

    Bookmark   July 19, 2003 at 9:43AM
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I lay flagstone in sand, and I prefer that look; but frost will eventually heave them up here and there, sometimes bringing them right up and placing them ontop the ground. Maybe the first year or two a table and chairs will sit nicely, but I always have a small pile of small stones on hand to level them.
Lazygardens is right, tho, about proper prep work and the thickness of the stone. It will help. Mortar,I think, is not a good idea, either.

    Bookmark   July 19, 2003 at 11:10PM
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Schoolhouse -
You are in Ohio ... the ground freezes solid there, and heaving is a fact of life.

Original poster and I are in areas where the ground doesn't freeze, or maybe the frost line is an inch down. If it's laid well, and it's thick enough, it's going to stay put.

    Bookmark   July 20, 2003 at 7:32AM
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colbyj(No. CA)

thanks for the very informative response and confirming my intuition that a sand-based flagstone patio should last a long time. I would like to tackle this project myself, and think laying it in sand would be much easier, plus I prefer that look. I just hope our landscape designer, who claims 30 years experience, is more knowledgeable in other areas than he is re: the flagstone patio.

    Bookmark   July 21, 2003 at 12:26AM
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Colby -
The large slabs are a bit harder to work with, but more likely to stay put than the cheaper bits and pieces.

I'm doing all the stone moving myself ... with a hand truck and crowbars. If I had one helper I would be done by now.

    Bookmark   July 21, 2003 at 8:42AM
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landscapers aren't always masons- and neither's any assurance that they know more than one way of doing things.

*falling to my knees* please, please, please don't imprision the rocks! if you're going to flag an area, do it on the sand bed, explain to your gardener that you're trying for a particular feeling in the seating area, and sometimes having to shim a table leg is a small price to pay for something that is such a pleasure to see : )

    Bookmark   July 21, 2003 at 1:57PM
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colbyj(No. CA)

chinacat--you may rise. have no fear, we now have our minds firmly set to do the patio in sand. the rocks will be free! :)

lazygardens--thanks for the additional tip. we like the looks of the big flagstone anyway, especially for the patio. it's too bad you are not closer, because I would donate my labor in exchange for knowledge and experience.

this weekend, we begin shopping for the flagstone. oh, what fun!

    Bookmark   July 22, 2003 at 12:55PM
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Elaine_LINY((I call it z6))

My patio is made of flagstones set into my rather compacted and sandy soil, which I screeded and tamped in places as needed. I'm so happy I didn't pour a concrete foundation, because who knows whether the next person that lives here is going to want it?

I dusted some sand/mortar mix from a bag, into the cracks nearest the door, which I knew I wasn't going to want to plant; wet, it makes a kind of fake mortar joint. It doesn't hold long but it discourages the weeds for a season or two, and it's easy to do. Easy to undo, just let it crumble.

But one mistake I made was to go ahead and use even the most acute-angled flagstones -- I wanted to minimize the cutting and I was proud of being able to do the jigsaw puzzle. These acute angles don't look right, even though they fit to the next rock pretty well. I don't think a "professional" would leave the sharp corners. I discovered that when the rocks shift, these points are always on the lifted side giving something nasty to trip over. Rounded contours don't give the same trip edge when the rocks shift.

Now all I need are some of these "sled" type chairs somebody mentioned so the chair legs don't catch on the cracks!

    Bookmark   August 10, 2003 at 3:30PM
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colbyj(No. CA)

Sled-type chairs--what a great idea! Thanks for the post, Elaine. We haven't yet gotten going on our patio, so I will keep in mind your tip on the sharp corners when it comes time to put together our "jigsaw puzzle."

    Bookmark   August 11, 2003 at 10:50AM
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I left the corners, although I did whack off any super sharp edges with a mallet. I adjusted the dirt under the stones to make sure that adjacent stones were at the same level. If you do the rounded install it takes a LOT more cutting and a lot more stone.

shot before gravel swept into cracks.

    Bookmark   August 11, 2003 at 3:07PM
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colbyj(No. CA)

lazygardens--when are we going to see a picture of the finished product? looking forward to it!

by the way, i read your website--i'm not totally clear on what you used for a base. i see what looks like a thin layer of dirt, but it looks like there is concrete under there?

    Bookmark   August 11, 2003 at 3:47PM
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I recently got a flagstone patio and sand was used. I think mortar is the best choice. If you live any where it rains your sand tends to wash down. You can't use a table or chairs. The surface is too uneven. I am going to redo my flagstone patio with mortar. I think more of a sandy mortar is what I will try. Maybe lightly dye the sandy mortar. I think a concrete looking will take away from the beauty of the flagstone.

    Bookmark   January 20, 2004 at 12:17AM
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There are two reasons that I know of for sand based patios, unless they want to grow plants in the joint spaces, or if they need the drainage.
If you are doing a patio with wide spaces in between (which I call meji) and don't plant to grid your stone so that the meji are small and refined (not that refined is allays better) then setting with large stones such as lazy gardens shows, then sand will be about the same cost as cement. If however don't want any frost heave or subsidence, then cement will actually be less expensive. You won't need as thick a stone (stone sells by the pound not the sq. ft)and the subsurface prep (if properly done) is less.
If you don't want to garden in between the stones you should also use cement. If you want to have green in between the stones (without gardening) use a slight depression in the grouting and include irrigation overspray onto the stones and grow moss... the looks is really great.
so I wouldn't say that you contractor is "Wrong" ... but given that you do want to do a lot of entertaining the only way to really guarantee that there will be no subsidence (as when you so entertain and have stones that are more than a .25 inch difference in height you will be liable for a hazard) even with the significantly difference in subsurface preparation is to use a cement base.
p.s. passion flower... you can use concrete color to (dye) your mortar... black powder is easily found in most hardware stores while the other colors can be found in at concrete plants (where cement truck come from). But when mixing test to see how much to use, it will look much lighter in mixing dry than it does once wet and then dried.
- Asha

    Bookmark   January 20, 2004 at 11:07AM
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"I am going to redo my flagstone patio with mortar."

To do this, you have ot take the flagstone OUT and lay it on a concrete slab. Just mortaring the joints will not work - they break and crack and crumble.

    Bookmark   January 20, 2004 at 7:09PM
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To do this, you have ot take the flagstone OUT and lay it on a concrete slab. Just mortaring the joints will not work - they break and crack and crumble

cracking and crumbling is not always a bad thing. If you grow moss there it actually helps... though of course a weed may find it's way to the ground and need to be weeded. You'd need the slab if you want to insure againse subsidence etc. but if it is only to resist the washout of sand that isn't necessary.j What would be easier than a mortar joint would be .25 inch minus gravel... that will hold in the rains and if it is basalt it will naturally be rather grey in appearance. These days people are learning the advantages of even laying stone in .25 -, (one quarter inche with the fine grains, the minus)minus rather than sand. All sand does not compact well - some sand is rather round while other sand is sharp... most sand in the US seems to be roundish and so it resists compatction. Another material for setting stone can be recycled ground concrete, ground to .25 minus.

    Bookmark   January 21, 2004 at 10:12AM
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mustangsally52(zn10 sfl)

can i just lay my flagstones in my very sandy soil and use gravel in between and then plant moss or low growing grass between the stones. I'm in south florida where I don't have the issue of frost.

    Bookmark   January 23, 2004 at 9:41AM
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depends, if you laid a stone flat on the beach, you probably wouldn'ty expect it to be very flat the next morning... when laying in sand of any type you need stones that are thicker and more broad to resist shifting when you step on them.
Also if they are thick enough and placed close together (.5 to .25 inches)the grout joint will help resist movement.

    Bookmark   January 23, 2004 at 11:13AM
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I'm wondering if those who are installing their dry lay flagstone patios for the first time realize what the sand bed is actually needed for ?
( obviously excluding Asha and LaLazyG. )

It's a setting bed. Used to assist the mason/ installer in plumbing and leveling out unevenly guaged stone.

Beach sand is not acceptable for this application because is has rounded edges. It can be used in a pinch if your setting bed is very thin - like 1/4 to 1/2" inch and preferably with a tad bit of a binder sifted in to keep the particles from shifting.

Always spec and use 'sharp' sand. It compacts well up to a 5 or 6 inch thickness , anything more than that and it has enough mass for a downward load to sift the particles .

For the best results the setting bed (sharp sand ) should be spread ontop of a non organically humic based ( because of decomposition = sinking ) of hard packed class II aggregate which is a combination of fines ( stone dust ) and sharp angled small rocks ( you can spec various sizes but the most common is 3/4" )

Your setting bed will eventually wash out if it is not contained on the outer perimeter.
This is why masons do one of several means to 'lock' in their setting beds ; A) install a perimeter footing, much like a curb ,
B) install a raised border of sorts - usually stone but sometimes wood or metal or plastic has been used.
C) mortar the outer perimeter flagstone joints as well as omit any escape joints between the sub base / sand and flagstone by damming it up.

The sand will evenually erode and filter down thru the subbase ( the highly compacted class II layer ) for this reason some masons install a filtration layer that allows water to percolate down but fine particles cannot.
This erosion seepage problem is caused by several factors and depending on your climatic location wll occur faster in some areas of the country than others - places with frost heaves , locations that receives very heavy fast hard down pours, flooding, excessive downward and sideward pressure from furniture/ people/ pets over a period of time , Inadequate sloping and or planned drainage exiting, ect....

The surface area of your flagstone patio is only as good as the effort that you put into your subbase.

    Bookmark   January 23, 2004 at 1:41PM
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colbyj(No. CA)

Is fill sand ok? This is what the stone yard recommended.


    Bookmark   January 23, 2004 at 1:47PM
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Fill sand is a generic term . Fill sand in Arizona will be different from fill sand in New England.
Depending on where this fill sand was dredged from ( Arroyos , creek beds are common dredging areas as is some beach areas and low lying areas within the quarry itself. )

Ask the supplier if it is Sharp or Coarse sand vs. rounded or beach sand.

    Bookmark   January 23, 2004 at 4:48PM
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colbyj(No. CA)

Thanks, Michelle. I confirmed with the stone yard that it is a coarse sand, so I should be ok. Flagstone comes tomorrow, so the adventure begins....

    Bookmark   January 23, 2004 at 4:56PM
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Mich -
Thanks. Yes, if I had a less casual attitude towards my atrium I would have added a layer of sand. It makes levelling the rocks a lot easier. Butthere is vrey little difference between my hard-packed dirt and a well-tamped sand bed.

Mustangsally -
"can i just lay my flagstones in my very sandy soil and use gravel in between and then plant moss or low growing grass between the stones."

Certainly ... the whole purpose of a cement slab and mortar is to minimize heaving in freezing climates. You will have to level the area and make sure it's well-packed. YOu might need ot use more sand under some of them to make the tops level.

    Bookmark   January 24, 2004 at 11:00AM
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BradSwanson(Zone 3, MN)

Live in Zone 3, north central Minnesota. Am going to construct a flagstone patio. Only have about 4 inches of top soil. Below that is pure sand, no clay, loam,black dirt of any kind. This sand goes down for at least 15 feet, maybe as far as 50 feet. Do I need to have any sort of gravel base or can I just pack the existing sand and lay the flagstone on it?

    Bookmark   February 27, 2004 at 5:57PM
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Brad -
I'd scrape off the topsoil, pack the sand well, and lay the stones on the sand. You might have to bring some sand in to level it or raise the level fo the patio, but it sounds like you have excellent drainage.

    Bookmark   February 28, 2004 at 9:06PM
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My wife and I built a flagstone patio a couple of years ago and it has held up well, using no mortar. Our climate in NC is fairly mild but we usually get 1-2 snows per winter and plenty of freezing nights. We have fairly heavy clay soil and dug it out so the space was level. Then I built a 2"x4" frame to contain the sand and leveled that as well. We bought bags of sand at Home Depot, but in retrospect I should have just bought a load in my pickup truck. It took a lot more sand than I realized and I ended up having to buy about 20 bags.

We used some flat limestone called Tennessee field stone for our patio. I had originally bought it to make some dry stack walls, but many of the pieces were so big and flat that we decided to use them for the patio and a path. After filling the wooden framework and leveling the sand, we set each piece of stone with a level. It is time consuming but fun -- sort of like a freeform jig saw puzzle. After laying all of the pieces, we spread more sand over the top and swept it off. The sand I used had a yellowish-orangish color that did not go well with the grey-brown rock, but it quickly discolored with dirt and such and now looks great.

Heavy rain sometimes washes some of the sand out between rocks, but all you do is add more sand and sweep it off. One of the real unexpected pleasures of the patio is that moss from the rocks has gradually started growing in the sand between the rocks. After 2 years, moss has filled in about 1/3 of the spaces. This fall we pinched little pieces from the mossy spots and planted them all around the patio. Hopefully it will fill in the rest of the way this year.

We have not had any trouble using furniture on our patio. We have 2 Adirondack chairs and a small table as well as lots of container plants. The size of the patio is about 8x16 feet. We have a small pond at one end. The patio gets a lot of use because it is just outside our back door and we have to cross it to reach the back yard or the pond. We also sit out there a lot.

My best is advice, if you are considering making a flagstone patio, is:
-- Use a level religiously for the base layer and laying the rocks.
-- Make sure you have a frame to contain the sand or it will seep out.
-- Have a base layer of sand at least 2" deep. Flagstone rocks vary in thickness and you need the sand to adjust heights to get them all level.
-- Take your time laying the rocks and fitting them together. If a stone "rocks" or totters, dig out or fill in sand underneath until you get it perfectly stableized. Use the level to make sure each rock is flat and no higher or lower than adjoining rocks.

I will try to post a photo later.

    Bookmark   March 9, 2004 at 8:28AM
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I'm installing a flagstone patio using redstone from one of the many quarries down the street. From the other messages it looks like my installation is different. For starters I'm using pea gravel not sand for the majority of my 4" base. And I'm cutting each piece to fit as close as I can make it.
I choose this method because I didn't like the way this redstone looked with mortar (colored or not), I didn't like gaps between the pavers creating an uneven walk, the sand between the pavers was messy and got into the house, and I wanted to be able to walk in bare feet on the pavers so that meant I did not want to use cruser stone (the breeze) as a filler.
When I bought this house the front side walks used small (1.5'x1.5') pieces of red pavers that looked to be as old as this house, 30yr. I noticed that the erosion occured not on the edges but that the pieces split creating two or more stones the same 2 dim size but thinner.

All of my "I don't like reasons" above came from these side walks, which I eventually removed and are currently re-doing. I use a lot of this older stone for small retaining walls for steps and cut in pieces between larger paver stone 2'x3'. So when friends ask what am using between the pavers I answer nothing.
My daughter was walking across the side walk in bare feet yesterday and descovered how great it felt, that made my day.

So far it been a real trip working with this red sandstone, I find that I can pretty much cut any shape I want assuming I keep note of fractures in existing piece and breadth of the cut, (can't get to narrow). I score every side and then get to work with my chisel and hammer, 20-30 hits, flip and repeat, flip repeat, etc. I find that you have to judge the force of the hammer carefully, getting fustrated and wacking gets costs time and money and it's been a lot of each.

    Bookmark   March 9, 2004 at 10:19PM
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I have two doggies, one loves to dig her slender long legs into the spaces between my sand-based flagstones and make piles. I'm hoping she grows out of this (she's 1 yr) but in the mean time I have tried growing moss, and recently, putting down large pebbles (1/4" - 1"). I love the look of the pebbles and I can only see one solution: put some type of permanent product down and imbed the small stones.
So, my question for the forum is:
1) What product can I use to "pour" in between the flagstones that I can imbed the pebbles in that will "stick"
2) Or, any other suggestions????

Thanks for entertaining my problem. It's a big one to me.

Warmest Regards to the group,


    Bookmark   April 5, 2004 at 10:27PM
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In 03 we had flagstone sidewalks put in.The one is breaking away already.Here in north with season changes is what did it.Theyre mortared.

    Bookmark   April 8, 2004 at 8:24AM
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I recently built a flagstone patio as well. I am in NC, for the base I used crushed quarry fines and sand on a slightly sloping area of my yard. At first I used the sand to fill in the joints between the flagstone. This did not work out well, with any heavy rain or high winds the loose sand in the joints would wash away or right on top of the patio itself, making it very uncomfortable to walk in with barefeet. I just recently started "redoing" the joints between the stones, I am clearing about 3-5 inches deep between each stone and brushing in quikcrete mortar. This so far seems to be doing the trick, it makes the patio much stronger/sturdier and I can now even walk on it without any shoes on. I like the flagstone look in the more natural sense, the patio is an extension off of a deck built mostly for looks, not for entertaining purposes. So I also like the "rough" lay of stone, not a perfectly level surface. Makes it appear to be much more natural. I have had several friends use sand as the joint filler as well only to be greatly disappointed. The mortar I feel is going to work well and will require less "fill in". I assume every year or 2 I will need to repair some cracks, but I think that is better than having to sweep in more sand after any heavy downpour.

    Bookmark   May 23, 2004 at 4:51PM
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I used decomposed granite, and that stuff after a couple rains, gets super hard, almost like concrete. Pretty amazing stuff.

I like the natural rough look too, that is how we did ours.

    Bookmark   May 24, 2004 at 11:12AM
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How do I make a pattern? I want the patio I build this weekend to fall where it may as the shapes take form. I don't know if I should start digging in the middle and work my way outward...I have a pallet full of flagstone, kinda medium to small pieces ranging from 1/2 and inch to 3 inches, 4 inches thick at the most. I plan to use left over sandbox sand. I also plan to plant some Irish moss between the cracks when done. I don't want my patio to be square, rectangle, orval..you get the idea....any advice? I am a first-timer at building one.

    Bookmark   June 3, 2004 at 10:20PM
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I bought the green steel edging from Home Depot. It comes in 10 ft lengths, I think its 4" high. We built a shape out of that stuff. Its very flexible.

Definitely make a shape first. You need some sort of edging, especially with sand.

    Bookmark   June 25, 2004 at 8:50AM
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zeuspaul(9b SoCal)

Don't start in the middle. Work the edges first to develop good lines (edges) and then fill in between.

    Bookmark   June 28, 2004 at 11:25PM
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Summer of 2003, we hired a contractor to build us a flagstone patio. The contractor used stone pavers as a retaining wall due to my yard being sloped. A sand base was used to lay the flagstones. Mortar was used in between the stones. Now, one year later, the mortar is breaking apart from the flagstones and crumbling. The flagstones on the end of the patio are completely loose and I fear someone will get hurt. Surprisingly, we have not lost very much sand. I do not want the expense involved to pour a cement foundation in which to lay the flagstones. Can I do anything else??? Thanks for any advice!!!

    Bookmark   July 8, 2004 at 3:47PM
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OUbrandy -
Call the contractor and let them know they have a job to fix.

It's possible to build a flagstone patio on a slope, but the retaining wall has to be well-built and the base has to be thoroughly compacted (layer by layer, with a machine).

    Bookmark   July 9, 2004 at 11:16PM
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Thank you, Lazygardens!!! I am very frustrated because the contractor is finding all sorts of reasons to put me off and not come back to my home. Unfortunately, I am meeting with an attorney this week, an option I didn't want to have to pursue.

    Bookmark   July 13, 2004 at 11:46AM
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calisto(z9 CA)

Three years ago, I created a 500 sq.ft. arizona sandstone front courtyard surrounded by a planted screen and beds. I hand leveled my patio area and laid a weedblock barrier and covered it with a four inch deep bed of fine grade sand - the one recommended by the supplier of stone. Use the supplier's sand, not playground or sandbox sand, it won't hold it's shape and form a firm bed to support the stones. Three years later the sand is firm, the stones beautiful but something just wasn't right. I use benefin (sold as AMAZE)in the spaces between the stones - I have never had any weeds. I have lived with it on sand and have hated it. Dirt is tracked into the house and I'm forever cleaning.

Recently I poured a six inch by six inch valley of mortar surround around the entire perimeter of the patio then mortared between all the stones with an already colored mortar. Now each stone has a reason for being. It's easier to wash off, it's easier to walk on, easier to set a table & chairs on - the whole thing is far more functional now.

There is no cement slab, no hardibacker board, only the ground that is hard as a rock to begin with. Now it's a patio that I can be on without having to worry about a chair fallng into a crack or someone tripping. The stone is beautiful and now I wish I had mortared years ago.

This is one approach. Thank you for reading.

    Bookmark   July 16, 2004 at 1:11AM
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I am finishing putting a retaining wall about 2.5ft tall and i plan on making a patio with flagstone, but dry laying them with about 2 in of sand beneath it and about 2ft of soil beneath that. I was going to make the flagstone as tight as i could and fill in the cracks with sand...is there any concern with that? Any advice how to level a 20 by 25 ft patio before taking a plate compactor to it? I also live in the chicagoland area with warm and very cold weather. ANY CONCERNS about anything that i describe...thanks for the advice...

    Bookmark   July 3, 2006 at 4:20AM
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I've done two different types of flagstone patios- love both. And being a woman of 5ft and doing it all myself ..a great project I could handle with min difficulty~
The front offsets a pea gravel courtyard, so I used a silver toned flagstone. After leveling, I laid down a weed barrier, then laid out my puzzel piece of the flagstone, butting up the edges close together. To solve the problem of the different depths of the flagstone, I kept a pail and shovel of pea gravel handy to lift up or remove to make the patio all level. When satisfied with the look, I then mixed pea gravel with a light dusting of quick cement and swept in between the flagstone. Then watered down. Later, I removed some of the rock/grout to insert small steppable plants here and there to make the patio blend into the courtyard garden. When I rake up small debris from the garden, I redistribute pea gravel all around, always creating a natural relaxed look to my front courtyard patio.
In back I wanted to do an outdoor kitchen/dining area. I leveled an area next to the deck with gravel,then crushed granite,packing down a hard surface also making sure it was above water level. (Oregon rain can create ponds where not wanted)Afer purchasing island grill and patio set, budget didn't allow for full flagstone patio set in motar, so next layer was a good garden blend, packed down as well. Then I chose a sandy brown color of flagstone, which blended colors from the teak furniture, the fencing, deck and marble topping of the grill unit. Also had some silver stone left over to reflect the stainless steel. So laid that out with large pieces together in the main walking areas and chair placements, non traffic areas wider for plant placement. Swept in more garden soil.Watered down the finished laid stones, making sure settled. Then filled in the cracks with steppable plants that became solid patches. If budget would've allowed, probably would've filled in with motar but loved the effect I ended up with as the patio borders also a Koi pond, so it still keeps in the theme of a relaxed grotto effect. My little paradise..always in progress :) ~ Ani

    Bookmark   July 3, 2006 at 2:09PM
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I am planning to lay a flagstone patio and walkway, so I've been asking everyone who knows anything about flagstone, questions....lots of questions. The general consensus seems to be that the stone needs to be mortared/cemented in order to put furniture, etc. on top. This is an area that is high traffic in/out of the house, so I don't want something messy. I'm planning to put 3" of crushed granite down, then a half inch mortar bed (actually portland cement mixed with mortar sand). If someone else in Texas has done this, I would love to hear your feedback. Thank you so much.

    Bookmark   July 17, 2006 at 4:18PM
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bailey_09(z9 Houston)

Sandy, I've installed at least a dozen flagstone patio's in the Houston area in the past 5 years and they have all been large to very large 1 1/2" - 2"thick stones on crushed granite gravel and sand; 1/2 have been grouted and 1/2 granite gravel fill. All the patio's have had seating and high traffic walk areas and I have not had any problems with movement.

If you are using small stones then you may need to anchor them. However you can do that by dry sprinkling the portland on top of the sand before you set the rock.

Personally, in seating areas I prefer to use very large flagstones.

    Bookmark   July 28, 2006 at 11:59PM
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Can anyone clear this up for me please?

I am going to dry-lay flagstone in my 320 sq ft patio and am confused about establishing the proper base. Living in the Dallas-Ft. Worth area, I am not concerned about freezing, so how far do I need to dig? I have read that I should pack at least a 4" gravel base, then 2" sand, then flagstone. How thick should the flagstone be? 1-1.5"? 2"? If I lay 2" stones, do I need to have as deep a base? Needless to say - the price of my stone may double depending on the answer. I recently was told that a couple of inches of sand as a base (and no gravel) is sufficient with 2" flagstone but I just don't know if this will be durable enough (at least 5-10 yrs). We will edge the patio and put down landscape fabric, too, and at the end fill the joints with decomposed granite.

Thanks in advance to anyone with insight!

    Bookmark   August 13, 2006 at 5:28PM
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I live in California and our yard that was not growing grass after 3 attempts of replacing new sod, so we decided to redo the entire backyard. We wanted a clean look and also a larger area for entertaining. So my Husband and I purchased flagstone to cover 1000sqft, it took a 5-6 weekends to finish. These stones weigh a ton it took two strong people to lift one piece sometimes, they were the thicker stone, 2-2.5 inches. We were told it would be better to lay in sand and they would be more stable. We didn't want spend more money to pour concrete, put drains in and then lay the stone on top, so we opted for sand setting.

Now that it is done, I find that maybe we should of done with the mortar instead. We used much much more sand then expected. The surface of the stone always looks dirty because the sand and especially since it's a large area sometimes people get there heels stuck in between them. Our neighbor has a huge ficus tree that drops berries and leaves that would get stuck in between. I find myself always sweeping outside. We don't have problems of them shifting too much, just occasional small pieces do come up. I think sand setting will work better for small areas but not large patio areas, we are going to mix some dilluted morter mix and pour them in between the joints, hopefully it will help the sand stay in place. I don't mind that there will be cracking, I just hate the having to sweep and getting things stuck between the joints. Rosa

    Bookmark   September 14, 2006 at 5:10PM
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I am planning to lay a flagstone patio and want it mortared so to use it for entertaining and have it be a "barefoot" patio. I'm in a zone 5 area-Utah with a fair amount of snow and freezing. Our plan is to lay down chicken wire in the middle of a sand and cement mixture (dry), place the flagstones (varied in sizes) on top, water to set the cement, and finally mortar between the stones. A couple questions: 1) Do you think this dry cement method with the chicken wire will hold up to the freezing and help prevent the mortar from cracking? 2) Any suggestions of getting a professional-looking level mortar without smearing it on the flagstone?

    Bookmark   September 20, 2006 at 12:18AM
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We all of you say mortered do you mean mixing 1 part portland cement with 3 parts sand. Putting it in dry then watering???

    Bookmark   October 8, 2006 at 9:23PM
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Yes, essentially, although we are planning to wet the mortar mix before putting it between the stones to make a stronger bond.

    Bookmark   October 9, 2006 at 11:44PM
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What would happen if you used dry morter in between the flagstone instead of sand? My flagstone is all set out over 4 inch of rock then 2 inches of sand. we put the weed barrier down next then the flagstone. I dont know what to put between them now. I live right on the Oregon coast. No freeze and my soil is pure sand to start with. Ideas.

    Bookmark   October 10, 2006 at 8:15AM
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Hi michelle2yard,
I'm also living in Utah and I'm looking at installing a 10x16 or so flagstone patio next summer. Have you installed yours yet? What did you do?

We already have a concrete patio that we want to build over and extend a little bit. What do you think would be the best way to do the patio and have a natural look? Is it possible to build a raised stone patio over this, about one or two steps high, without having to use a ton of concrete? Thanks!

    Bookmark   November 10, 2006 at 6:26PM
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We just had a flagstone path laid over pea gravel and joints were filled with fines. The fines are coming out of the joints and spreading over the surface of the flagstone making walking barefoot difficult and tracking fines into the house. What can we do to keep the fines in the spaces between the joints?

    Bookmark   April 25, 2008 at 10:01AM
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dougy2040(zone 6)

look on the internet, for polymeric sand or lock joint sand. It will stay in the cracks, but can also be moved around and smoothed again and again. It is not affected by getting wet or freezing. When it gets wet and drys out, it stays firm. Then it can be broken loose again, to sandy powder and moved and swept into the cracks again or repositioned. Next time it is damped, it firms up again.
Probably is available a masonry supply store

    Bookmark   April 30, 2008 at 5:35PM
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I have a question about replacing my old wood deck. I would like to replace it with a raised patio. I know there are some synthetic stone like materials that can be used. The deck is 4-6 feet off the ground. I've contacted some local deck people but they only deal with wood. I think the raised patio with the synthetic stone like material is a new trend and can't find much info.

    Bookmark   May 18, 2008 at 7:58AM
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Can you just set fieldstone in cement when you are pouring it?

    Bookmark   May 19, 2008 at 4:27PM
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I have a previously built patio of flagstone with pea gravel in the joints (large joints in places, jigsaw pattern). I have decided I don't want the pea gravel anymore, I want a more finished look that is easier to sweep clean and to walk on. I have been thinking about using the polysand, but have read a lot of negative comments from landscapers who used it, saying it has to be absolutely dry and the dust tends to stick onto things and not come off, etc. Now I am having second thoughts. After reading all the above posts, I am wondering about crushed granite and sharp (torpedo sand). I also read good comments about a product called stabilized crushed stone by a Canadian company called Envirobond. I would have to find a distributer about 2 hours away to get that. So you can't just sweep a sand/portland mix in a area the freeze/thaws and expect it not to crack?

    Bookmark   July 5, 2008 at 10:57AM
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Kaydye, I live in your zone too. Short answer to your question is no. I bought my house two years ago.. the owner installed a flagstone patio with the sand/portland mix just before selling. After two winters, the thing is cracking apart, to the point that parts are unstable and a trip hazard. The joints seem wide to me, about 2.5 inches.
I found this thread, doing research about how to replace it with something that will last better. I am probably going to go with the sharp sand and crushed granite. I think the cracks look terrible. My house is also built on a hillside, so between the slope and freeze/thaw cycle, even a cement base for the stones would eventually crack.

    Bookmark   July 8, 2008 at 11:49AM
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Looking for moonchildani, if she's still around ... I'm also in Portland and want to ask a couple questions.

Or, for anyone out there, I didn't put a border around my patio area. Already have it dug out to about 3 inches deep, weed barrier down, quarter-minus over that, then sand. Can I assemble the flagstones, fill in the gaps with sand and then later put a border around to keep the sand from migrating out or washing out during Portland's rainy winter?

The patio's against the house, so it has a slope away frm the foundation and toward the backyard grass. The finished flagstone area shouldn't be higher than the level of the grass itself, will that hold the sand in?

    Bookmark   July 9, 2008 at 10:38PM
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I just built a quartzite patio in Reno, NV. I used the new product, polymeric sand and it worked great! I got the sand in 60 lb bags for $20 a bag from Home Depot. My patio is 9X27.5 and I used 5 bags. It looks like regular sand and sweeps into the joints. You then mist it 3-4 times waiting about 10 minutes between each misting. The water activates a weak polymer glue and locks the sand granules in place. We don't have much problems with frost heaves here, but if a stone moves you can pull up the sand in chunks and step on it or use a shovel to get it back to a granular stage, sweep it back in place and re-mist. Although the polymeric sand sets up pretty hard I don't think it would stand up to a leg from a patio chair, etc., so we plan on getting sled style chairs for the patio. It does do well with walking on it and the sand stays put! So far we are very happy with it. I'll let you know how it goes thru the winter. We get very little rain here but we do get snow.

    Bookmark   September 24, 2008 at 6:44AM
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I have some polymeric sand that I've not tried yet, but I will say that with the stone dust that we used to fill the gaps, it does get a bit messy, as it moves around under use and has a bit of an unfinished look, here's some pictures and my article on how to build a stone patio (link below).--Peter

Here is a link that might be useful: How to Build a Stone Patio

    Bookmark   February 11, 2009 at 7:51PM
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We live in Arizona and laying a flagstone patio...the joints vary in width, some fairly wide and others not so wide. We would like to cement it a color compatible with the stone...what is the best product to use for mortaring the joints?

    Bookmark   June 17, 2010 at 1:52AM
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We bought a house in which a large courtyard patio of irregular stones had been created by cementing the stones over an existing concrete base. Unfortuately, the installer didn't know what he was doing and created a smaller area smack in the middle of the patio, which was below the grade of the rest of the patio by an inch plus or minus. The result is a lake in the middle of the patio every time it rains. I can't afford to tear the whole thing out, but is it feasible to rip up the stones in that middle area and replace them with similar stones (the house has a large pile of unused stones) over a sand/gravel bed?

    Bookmark   March 17, 2011 at 3:37AM
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Tom, I would think you should be able to pull up the stones in the area that is low and raise it with cement or possibly mortar. Might even want to make it 1/2 inch or so higher in the middle and grade it down to the other to make the water run off. Just my .02

    Bookmark   March 23, 2011 at 10:18AM
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I live in Missouri where we have temperatures both hot and cold. I have dug out my base, approximately 4 inches deep. I would like to do grass in between the stones as I prefer the natural look that I hope that would create. The soil is quite compacted below, but I am not sure what to do next. Should I use a few inches of AB3 (stone dust and sharp edged gravel mix) or sand, or both. Also, what do I do about soil for the grass to grow in? Any help would be greatly appreciated.

    Bookmark   July 18, 2011 at 12:33PM
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