How to Build a Stone Patio

Installing Stone Patio
With so many articles out there on "How to Build a Stone Patio" it will be a wonder if you find this article. But I hope you do, because from my pre-project research for "flagstone patio design", "flag stone patio designs", "landscape patio design", and other searches, I don't think I fully understood the scope of this project. Hopefully this article will help you understand the process of building a stone patio more clearly than what I found from the basic tutorials on the web.


Here is a "close to final" after photo of our stone patio build. The stone is natural, irregular bluestone, which is considered a type of flagstone, that has been "tumbled" with water so that the edges are rounded and have a worn look, much nicer on the feet, than catching a sharp edge. Keep in mind that irregular natural stone will have more tendency to catch your patio chair feet when moving around in your chair, and will be less forgiving for high heels, than using a stone that is cut, smooth, shapes. (Click photos to enlarge them)


Here is the before photo. We had a pea stone pit.

Actually, I always said, "if I ever write an article about how to build a patio, I'm going to start by asking the reader why the hell they want to build a patio themselves?" And then I was going to say, "okay, you want to build a patio, okay, you are an idiot!".

BUT... Now that it's been a few seasons since the building work is behind me, I love the patio. I'm proud of it, and happy that I did the work myself. So if you are a glutton for punishment and you don't mind busting your butt for 10 days, then go for it! You'll be very happen when your done!

Step 1. Measure and Create a Plan for your Patio Design

From your flagstone patio design plan, you will be able to determine the square footage of your patio, and thus will be able to calculate the amount of materials you will need (see foundation diagram below to calculate patio depth). I did this for my patio on the computer using drawing programs, but graph paper will work nicely too. If you want to get fancy you can also try Google Sketchup, which allows you to draw in 3D and offers a free download version for PC and Mac.

Note: During your planning phase, it's very important to have local utility companies check to see that there aren't underground power lines, communication cables, gas lines, and water lines in the area you plan to excavate. Google "before you dig and your state" to see what programs you can call for locating utilities in your area. If you don't, you risk: Death, injury to you or others, disruption of services, and other bad things.

Step 2. How to Determine Sub-slab Patio Foundation Depth and Materials for Your Region
Every book you read, internet article, friend, etc. will tell you something different. Run down to your local landscaping, stone, masonry dealer and ask them if they install patios. If they do, ask them what they recommend for stone patio sub-slab foundation depths and materials. There's no set answer to this, as every region has it's own climate and thus it's own physical abuse the patio must endure. Here in Northern New England it was recommended that I build a 12" gravel foundation (this is a aggregate mix of crushed rock that includes, varied sizes and, "fines", fine rock dust and particles. If you didn't have this mix of material it would not be compatible), with 1.5" of sand on top, with the patio stones on top of that, and then to fill the gaps between stones with stone dust. We have serious winter frost heaving issues here, that's why the foundation is so deep.

Dry Set Flagstone Patio Base Cross Section Diagram

My patio rendering diagram shows a cross section of all materials used in a "dry laid", or "dry set", bluestone patio base (meaning the sub-slab is not concrete or mortar). Other flag stone patio designs are set on concrete slabs, but are not within the scope of this article.

Step 3: How to Estimate Costs for your Stone Patio Design
Now that you've asked the local experts about the sub-slab foundation depth and materials, and you know the square footage of your plan, then you can calculate the materials price list for your patio. To calculate materials: (patio length ft). x (patio width ft.) x (depth of material layer ft.) = cubic feet of that material needed. Stone dealers work in "cubic yards" and want you to order that way. To calculate cubic yards: (cubic feet of material needed) / (27) and then round up to the next cubic yard.

Example
For a 20 feet long by 20 feet wide patio with a 6 inch deep layer of gravel: (20' x 20' x .5' = 200 cubic feet. 200 / 27 = 7.4 cubic yards. Then round up to 8 cubic yards of gravel.

Alternatively you can have your stone dealer do the math from your measurements. Remember too when you order your materials they will measure and load them on their truck uncompacted. So order more, as you will be compacting your materials. I couldn't find any good math on calculating this in, but it seemed to be true in my case, as I ran short on all materials. Ask your stone dealer about this. They may have a good answer.

Add to that price, landscaping fabric, which should go between the sub soil and your foundation, and landscaping fabric staples to hold the fabric up on the sides before the hole is filled.

And...
You'll need to rent a vibratory plate compactor, and perhaps a small walk behind Bobcat or a standard Bobcat, or if your not into running heavy equipment, high someone to excavate for you. If you are only building a small patio, or if the foundation doesn't need to be too deep, have at it, with a shovel. I could never have completed our patio without the rental of the walk behind Bobcat (needed to move in tight spaces), to first excavate the gravel and soil, and secondly to bring gravel back into the hole. We ending up renting the Bobcat for I believe 4 days, at $140 a day. The plate compactor will run you about $65 per day. We needed the compactor for 4 days as well... The scope of your project will dictate machine needs.

And...
You'll also need to calculate in tool purchases. Photos and caption are coming.

Stone Patio Sticker Shock
You might have it at this point. I did, and asked my materials supplier what it might cost to have them build it. They said, "figure your material cost, then double it, then add yet another half".

Step 4: Ordering and Delivery of Stone Patio Materials
Keep in mind that stone dealers charge not only for materials, but also for delivery. The closer you are to them, the cheaper the delivery price, so find someone local. The gravel will be one truck, the sand other and the stone dust another, as they can't mix them in the dump truck. The stones themselves will come on a flatbed truck, on pallets, and will be placed on your site by a fancy forklift.

If you are not sure on exactly how much material you need, err on the side of more, rather than less. If you have a place to keep the extra materials, you'll find they come in handy for other projects later. I also use the extra stone dust I had to replenish it between stones as needed. If you end up with lots of extra, you can place a sign at the end of your driveway offering "free materials". Much worse is having work stop because you didn't order enough gravel. I did that.

You'll also need to determine where you want the materials dumped. They'll be coming with dump trucks, so they'll need access. You'll want the materials near the patio build site as well.

Step 5. How to Stake-out the Patio Perimeter

You'll need 2" x 2" stakes with pointy ends (cut them on 2 sides to form a point, if you only cut them on one side, they will move off center when you drive them) that you can drive deep enough into the ground that they'll be truly solid, as they will take a beating during the build. Determine your corner points, and then use a sledge hammer to drive the stakes into the ground about 10" beyond your corner points. You put the stakes farther out (if you have room) so that you can dig and work near the stakes without disturbing them. You'll have to fill that area with foundation gravel, so don't go too far out.

Tie "Mason's String" (neon colored string, that doesn't stretch or sag), tightly between the stakes. Use a "Line Level" hung on the strings to determine level and also to determine slope of the patio for drainage (1/4" per foot). The line level will have that pitch marked on it.

Dig out the foundation area to the depth you need (foundation, plus sand, plus rock thickness). Do not disturb the sub soil surface below. If you do, you'll need to compact that down too. If you don't, that looser soil will later settle and your patio will sink in those spots.

(Note: Decide what you are going to do with the excavated soil. You'll have quite a pile of soil to deal this. I was lucky enough to have access to the woods where I made pile should I need it later. You might consider using it to raise areas of your property. Keep in mind only the top portion will be good grass growing topsoil, and it will be hard to keep seperated, so consider it fill, that you later cover with a layer of good growing top soil.)

With a black permanent marker, mark the levels for the "top of the stones", "top of the sand", top of the gravel" on each stake. You will later use the mason's string at those marks to determine material height for each layer.

Step 6. Put Down Landscaping Fabric

After moving your strings down to see that your hole is deep enough, move the strings back up, or remove them and add landscaping fabric. I'd go up the sides too (you can use special landscaping fabric staples to hold it in place on the side, which really helps on windy days). The fabric keeps sub-soil from migrating up into your foundation, and keeps the foundation gravel from migrating down. Cut the fabric to go around the stakes as necessary.

Step 7. Add Intermediate Stakes and Then Gravel

Depending on the size and design of your stone patio, you may need to add more stakes. Mark these stakes from the mason strings already in place with a black marker, then add mason string across the middle of your patio layout in both directions.

Start bringing in your compatible gravel in 2"-3" layers. Spread it around with a metal rake (not the leaf rake type) and use a plate compactor (rental) to compact the gravel. You should make multiple passes in various directions back and forth, round and round, to really get the gravel compacted. If you skimp, your patio will sink in spots later.

Have a partner mist water from a hose before and during compacting. This helps with dust, keeps the compactor moving forward, and helps with the compacting process. Too much water and you'll get mud, and a stuck compactor. If you try to compact more than 2-3" of gravel at a time, the compactor will not be able to do a good job. It's very time consuming to compact each layer, but absolutely necessary. Move your strings up as you add more layers of gravel to check for fill height. You should also check for level with a long 2x4, or a couple of 2x4 screwed together. You can place a long bubble level on top of your 2x4. It's a good idea to let it rain a few times before you set your stone. This really helps to let the base settle, removing any air pockets. Or you can soak the base down a few times with a hose, just avoid a direct stream to the base. The official term for this technique is hydrocompaction.


In my case I was working in a confined space. I removed a few fence sections for access.


Here you can see stakes in place and excavation in progress. The area to the right will become a garden. You may have to use more stakes and strings than my diagram shows depending on the complexity of your job. Here you can see I have a few lines running, and a few stakes in the middle to check how far I've excavated.


We rented this walk behind Bobcat that was essential for this project. I had thought at one time to dig it out by hand, and later laughed as I realized that would not have been possible. The Bobcat was also a great help in getting gravel into the hole. I think we rented the Bobcat for 4 days at about $140? a day? I'd never run one, and made some mistakes in the first hour, but by the end, I was showing off my skills. They are fun, but make no mistake, these are very powerful machines and you must keep your wits about you. It would be easy to back up over yourself.


After adding 5 or so layers of gravel and moving the strings up each time to check for level, we took a break and laid a few stones out to dream about how the finished patio might look.


I believe this is the sand layer. I'm checking for level with a few 2x4s put together to for a long straight edge. You can use a level on top of the 2x4s too.


In the background you can see the delivery of two and a half pallets of tumbled irregular bluestone. Around this stage we took off a few weeks, which was a good thing, as it rained a few times which really helps to settle the base and remove any remaining air pockets that didn't get compacted.

Here you can also see the plumping (white hooped pipe) and electrical that I ran under the patio while it was open. My plan was to have an outdoor kitchen in that area. I used Pex Tubing for the cold only water supply, which runs through my basement sill and taps into my domestic cold water pipes.


When I first jumped into this project, I didn't realize some of the bumps in the road I would encounter. After figuring out a reasonable slope for runoff, it turned out that the patio side by the fence/driveway would have to be much lower than before, when gavel was there. I had to build a cement retaining wall to hold up the now much higher driveway.

I don't have photos of it, but on the other side of the patio, the same problem came, but in opposite. I had to add an extra step to our stone stairs leading to the back yard, as the correct level and slope made the patio stones about a step higher than our existing top step.

Also note the left side of the photo, which is the driveway, as you start to layout stones, you will want to get stones off the pallets, so that you can see what sizes and shapes you have to work with. The stones and dirt was everywhere. It seemed we had way too many stones, and it also seemed the driveway would never be the same again. Both turned out to be wrong. We ended up short on stones, and the driveway cleaned up just fine, after lots of shoveling, sweeping and hosing.

Step 8: Laying Out the Natural Stones

What a joy it is to be done with the foundation and on to the fun part... puzzling in the irregular natural stones. Rats@! It's not really fun at all. I thought this would go quickly and we'd see the natural stone patio take shape before our eyes... Not true. This is may be the hardest part of the whole patio project. Imagine getting a large pile of rocks, each one weighing "a lot", and you are too complete a puzzle with a 1/4" space between puzzle pieces... only the puzzle manufacturer took no interest in giving you pieces that actually fit together! Holey Moley! I started on a section, than would get to a road block, then start another section, and have to take it all up, repeat.

I didn't know if I should start from the center or from the edges. I choose the edges, as that's what you do with puzzles. Wrong! This didn't work well I didn't like that all the pieces on the sides were square. I was creating a border I never intended. So I took those all up and did a few Googlings that relieved nothing on "how to place irregular natural stones in a patio". I then started in the middle and things got a bit better, but not much.

If I placed five pieces, I'd feel great satisfaction, and sit back to admire my work. But if you stop, the patio is not getting done... This is VERY slow and challenging work. The guys at the stone shop told me I should shoot for 1/4" inch between stones. I'm not sure what planet that they came from and I very good at Tetris, but this was mission, almost, impossible.

After a few full days of toiling and trying to keep quality control to a maximum, my wife came out and placed a whole section fairly quickly that didn't meet my spacing standards. But she had a section done, so I left them! After seeing that performance, I too started to cut some corners. Sometimes a stone fits and sometimes it doesn't and sometimes you have to remove 5 perfectly placed stones because you are stuck. You remove them and try something else.

Somehow, in the end they all fit! I know I could have cut the stones, but that would have left straight cuts that would not have looked right.


Here's a shot the new garden space that echos what was on the right side of the steps.


Here I have all the remaining puzzle pieces spread out to look at. You see a space and you think things like, "it's kinda like Nevada, but wider" and then you go in search of that stone... Good luck! I now have huge appreciation for anyone that does stone masonry work. It really is an artform, and I think that is why I couldn't find much on the art of laying irregular stone on the web. It's a Zen thing. You have to be one with the stones.


And can you believe it! All the stones have been used. Somehow I did get a package of stones that all go together. Actually I ran short and had to purchase individual stones for the remaining spots around the edges. Some of these edge stones didn't fit perfectly, so I used a diamond blade in my circular saw to cut the edges. It's very dusty and stone bits fly around, so wear a dust mask and goggles when you cut stone.

After all of the natural stones had been laid, I nestled them in with a few loving blows from a dead blow hammer. Do this with a level in hand to convince any high points to lower. Other places you may need to raise a bit with sand.

After that I added stone dust to the patio and spread it around to go in, and under, the voids between stones with a broom. You should also gentle spray water over the patio to encourage the stone dust to find a compacted home, but be very careful not to apply a stream directly to the gaps, or else the stone dust and sand will start coming up, and it ruins the stone dust only color when sand is mixed in. If you want mosses or other vegetation to grow between the rocks, use topsoil instead of stone dust.

You can also top off the gaps with a final 1/4" layer of Polymeric Sand. It has polymers which when wet, forms hard, similar to grout. I planned on doing this, but Googling reveal difficulty in working with it. Basically some found that if you had any polymeric sand dust on your stones, it would become hard and stick to the stone tops. I've not tried it, but I may try a section. It would be nice to finish off what I have there now, which is stone dust, that tends to spread around on the surface a bit.


As the patio on the driveway side was now much lower. I had to build a step down to the patio from the driveway.


Here's my little helper.






A few more views of the almost finished flagstone stone patio. I have plans to possibly add some semi cement like sand between the stones, but I'm okay with the look for now. More on this later.

So far the patio has been through 2 winters and nothing has budged.


Why Building Our Flagstone Patio Might be More Difficult than Building Your Patio.
1. We had to lay a very deep foundation, as the freezing and thawing of New England is not easy on patios.
2. We choose to use irregular stone for our patio. If you want to make it much easier, choose a square or rectangle cut stone, to avoid the puzzle piecing needed with irregular shapes.
3. We built our patio in a predefined space, which presented unforeseen snafus.
3. Every project has it's unforeseen snafus, and you may have less than we did. But you'll have yours for sure.

Installing Stone Patio Resources
Popular Mechanics: Build Your Own Natural Stone Patio
The Family Handyman: How to Build a Stone and Brick Patio: Plans and Instructions
The Family Handyman: Build a Flagstone and Stone Block Patio
Ask the Builder: Patios 101 (Patio repair, How to Build a Flagstone Patio, Patio Design, etc.)
This Old House: How to Lay a Stone Patio
Ron Hazelton: How to Build a Patio from Concrete Pavers
A-Stone, Inc.: How to Build a Dry Stone Patio

My Standard Disclaimer: This is what I did. This does not mean this is the best way, the right way, to building code, or even safe for your needs. So you are on your own with your project. I make no promises about the information presented here. I'm just a do-it-yourselfer, not a professional at all, sharing my story. So if something goes wrong with your project, you are on your own. Good luck, and have fun!

All content and photos, copyright 2009, Dover Projects
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