What type of cement should i use for flagstone

Mix up a soupy mixture of 1 part Portland cement and 1 part sand. Using a grout bag, fill in the space between the stones slightly above the stones. Be careful not to get grout on surface of the stone. When you have used up one full grout bag, use a slicker or narrow trowel to press the cement between the stones. Scrape off any excess cement and sponge the stones clean. Move on to the next area. Once you have finished grouting all of the stones and as soon as the cement is hard enough, wash down the area by using a stiff brush or even a wire brush and plenty of water.

However, the closer you fit irregularly shaped stones, the more cutting and fitting you will have to do. If the sun is hot, keep the concrete slab damp with a spray mist. So it will not draw the moisture out of the cement to fast. If you can shade the area you are working, it would be better.

We do not recommend this process to someone who is not familiar with working with cement. Use expansion joints when pouring next to house or other existing concrete. Rockville - Frederick - Flagstone on Concrete Base. Construction First, lay out the area of the patio. It will not. Hello Devin, Your info is great on here but I have a unique situation. About 15 yrs ago, we put a paver and brick patio over a flagstone patio.

The flagstone was a mess and the patio was too low. They filled the joints with what I think they said was portland cement and coarse sand that had shell bits in it.

I am not sure about that but I need to repair some sections. I have no idea what to use. I am in South FL and I was thinking of stone dust but will that hold with the base of another patio? I am at a total loss. The fill was a light gray color that has lightened over the years. I liked that it had texture to it. Any suggestions would be greatly appreciated. If you want to set up a phone consultation, then email me photos, before and after if possible. My answer will likely be clean out the old joint material and replace with stone dust.

Since this is a paver patio though…. In Florida, 4 inches of road base will be plenty. Lay out your flagstones on top of your foundation and then level each stone individual in More info And a bit more. Decomposed granite for leveler, and joints. As far as the border goes, you can just glue your pavers down with liquid nails. Good point. Stone dust has many names and is available just about anywhere in the us.

Devine has saved me from the same fate! The road base turned out to be only ONE inch and the sand was inches. That is, after I had them take out the sand—but of course, there is still much sand remaining. I am trying to do this myself. I would hire Devine is a second if he were several states closer. Devine you have been a godsend! Your system of using stone dust for the joint filler is the best method, is there any way to get a different color established with using it to match different shaded flagstone.

You mean a way to get the stone dust to a particular color—in order to get it to match the tone of your flagstone? Anywhere local you recommend? Buy it by the yard. I have a field stone walkway on a slope that is laid on a base of stone dust and using stone dust between joints. Problem I have is that the stone dust between joints washes out after a rain and I have to add more stone dust several times a year. I want to use polymetric sand to seal the joints and make them more waterproof.

Do you recommend? A the joints may be too wide. I prefer to keep my flagstone joints pink-width. Thumb-width is good too.

I tell my customers that usually we can expect that a flagstone patio or walkway could use a joint top up once or twice a year. You want your joints recessed a bit anyway. In my experience, the joints often need less and less topping off as the years go by.

The stone dusts settles over the years, locks in tighter. Ambient dust gets in there and helps bind it up a bit. Moss may up residence. Should be 20 minutes of sweeping and hosing per year…. Yes, whenever I do jobs in New York this is what I buy. Hi Devin, Thank you for this post about using rock screenings to fill the gaps. We had a flagstone patio professionally done for us this past summer. He used the local roadbase — gravel and soil to level the grade and lay the flagstone, and then went over it with a compactor.

The problem is that we have mud, dust, and loose gravel everywhere. Some of the gaps between stone are more than an inch wide. How would you approach filling the gaps with screenings. A sweeping and topping off? Or some other method? Thank you for your expertise. Sorry to hear your difficulties. I just take a shop broom and brush the screenings across the flagstones, back and forth until the gaps between the stones are filled to the top.

Do this for the whole patio, Gathering the extra screenings into a pile then into a bucket and out of the way.

Then soak the whole patio with a hose on shower setting or similar….. I just had 2 areas of my patio done professionally in flag stone He used sand as a base, the joints were filled with pea rock.

The problem is that the pea rock is coming out of the joints. How wide are the joints, is it pattern-cut flagstone or irregular flagstone and is your region warm enough that sand is actually a proper foundation? All these questions are more can be solved with a photo and a location. If the joints are tight, stone dust might be the way to go.

Or moss, clover, irish moss, or some other ground cover. But pea gravel. Pshhh, nope. And on sand? Not in my hardiness zone. When I call around in my area and ask if they have stone dust or screenings, they say they have Is that the same thing? They also mention manufactured sand apparently very fine limestone. I have as my base and am looking for something for my joints.

You must be from the South. Yes, same thing. You get much wider than 2 inches or so, and you tend to get into problems. Hi Devin, great information!

What size gravel do you recommend to use underneath the flagstone as foundation? Some places will call it crusher run, or paver base…. The foundation will be crushed stone and screenings. Any thought on my solution? If using membrane at all. Fact is, you could probably get away with gluing directly to the pt lumber. But lumber can shrink and swell, even pt lumber, over years.

Have you dealt with gophers? Can you recommend best patio choice and method of installation for unstable land and gophers? But I do communicate with people across the usa and have heard of using chicken wire as an underlayment and as a perimeter. Like an underground fence.

Of course peppermint oil, hot sauce, loose tobacco and etc are all things that will help keep the gophers away. Maybe use the peppermint for a month or so to get them away from the area—then build, using the wire underlayment.

I like your recommendations of using screenings over base rock with the screenings also used in the joints. I hate plastic bender board but a lot of the pros use it.

Will that work to retain the path and patio? Any suggestions? Also, would you use a weed cloth in between the gravel and the leveling screenings? Weed cloth is used underneath flagstone, usually not to prevent weeds it does NOT prevent weeds anyway but to stabilize the soil in places that have a freeze thaw, like in Pennsylvania—not santa cruz.

In short; just use larger and thicker stones at the edge of your patio or walkway. Any stone at the edge ought to be at least one square foot in surface area. Smaller stones can be used in the center of the patio or walkway, but larger ones for the borders. A river rock edge could also be used.

You can also use smaller pieces of flagstone, laid on edge like a a curb stone and buried over halfway into the ground, as an edging. But again, use big enough stones on the border, and no edging will be required. Follow the above link for more detail on this issue. Properly laid flagstone does not need any edging. It takes a bit of skill…. Attention universe: I would like to travel.

There seems to be a lack of flagstone pros in this world. Give me a place to stay for the duration of the project and I can travel to your location—might not cost as much as you think.

Oh—sorry to hear that. I do travel for work, and I do offer professional assistance for DIY hardscape projects, so me paying you a visit is possible. Thanks for sharing all of your expertise, Devine. I completely forgot to use the weed barrier on my project.

Will this present a major problem? I sometimes use filter fabric between the soil and gravel—this does nothing at all to prevent weeds, and is considered unnecessary and inessential. The filter fabric can possibly help minimize future maintenance and can help to stabilize soils which are prone to movement or excessive dampness.

Thank you, this answered my question about using weed barrier. Hi Devin, do you recommend using weed cloth between the stone dust and base rock? If no weed cloth will the stone dust filter down into the base rock layer over time? What do you mean by base rock? I have never once laid landscape fabric between the gravel foundation and the stone dust bedding.

I well compact my sub grade, well compact my gravel base, and I do not worry about transmigration of soils. My older flagstone patios that had a layer of fabric beneath the gravel, are in great condition, still.

My newer jobs, from the past 5 years or so that usually forgo the fabric, are also in great condition. Fabric: usually, not so critical. Or surface run-off. Or if the area with have vehicular traffic. Or if there are trees nearby that have aggressive roots—anytime that I wish to give the gravel foundation more stability than is normally called for. The base rock must be a CA term for crushed rock and stone dust mixture and it compacts quite well.

I have a flag stone area in my back Yard. The weeds keep coming up through the sand. I have used different sand and would like to know what to do. There was never a fabric cloth used by the professionals.

I have taken the sand out of the seems and have all the weeds removed. What can I do next to ake my area look great again. Re-fill in the cracks between your flagstone with stone dust and if weeds ever grow there again, just pour boiling water on them to kill them. Weed fabric underneath your flagstone will not help really anyway. Any weeds that can live in sand and that have roots that will penetrate beneath the sand and the gravel, will already have a few inches of root buried and will live in spite of the fabric….

Stone dust is a better material for your flagstone joints than sand, and boiling water will handle weeds. Good luck with your flagstone! Devin, you have some really good information here! I have been in our home about a year Triangle area, NC , and thought I was being smart and saving money in the Fall when I had a lot of yard leveling done — they had machinery so I had them dig out our sq ft patio area.

Has been a nightmare to keep it dry, and been largely having to pump water out whenever it rains. Also, being told that gravel base vs concrete pad will eventually get sink holes beneath it as water drains through it.

Is that right? Dig it out with a steeper slant and remove anything that may be obstructing the downhill flow of surface water.

And let it sit for weeks, if you can. Probably, the soil will simply need to be excavated further, until you hit stable soil. The subsoil, the earth beneath your foundation should be stable and well compacted.

Wet clay is doughy and no amount of tamping will help. Trying to lay gravel on top of damp, doughy clay just does not work. To lay a gravel foundation on top of wet clay, you will have to dig down. About as far as it takes. Might be a foot down. When the soil is starting to get more solid, less spongey, you can then lightly tamp it.

Or let it sit in the sun to dry for a few hours, and then tamp. Lightly is key, with damp clay soil. Tamping it too hard will just make the situation worse. Now take the dryer soil from your excavation and add gravel to it and mix it up a bit. Lay four inches of gravelly soil, then lightly tamp.

Your actual gravel foundation should be thicker than usual. By the time you get to the top couple of lifts you should be feeling stable. Step there. The stability test is what it is all about. The whole thing you are trying to avoid is a spongey foundation. What you are looking for is for it to simply feel nice and sturdy underfoot.

Numbers are approximate, you have to do it by feel. As for your last question, well, for my opinion on the matter of gravel foundation versus concrete foundation, I direct you to this post:. Seriously, sink holes? You should also beware of quick sand and icebergs. Have heart then, for a well built dry stone patio will serve you for decades in good stead.

Hey Devine, first of all thanks for all the informative posts! I live in Southern New Mexico where unlike PA we may not have the extreme cold although we do get below the freezing mark , but do get extremely dry heat which has the adverse effect on concrete in which it will expand slightly. So I am about to lay some flagstone in my front yard which is largely xeriscape, but have a couple of concerns that I was hoping you could help ease.

I have seen instances where the stone dust will shift down ending up near the bottom of the slope leaving a mess covering the bottom flagstone and the top flagstone spacing empty. Any way to avoid this? Another issue that concerns me is that in my region we get extremely high winds, which not only carries in a lot of fine sand, but will also move out a lot of the finer materials. Do you believe that this will this cause any cosmetic or functional issues? Lastly due to my xeriscape yard, in order to remove leaves or other debris I must use a blower to remove from the gravel, and am worried I would find myself constantly refilling the stone dust after maintaining my yard, should this even be a concern?

How steep is the slope? Anmd how much rain do you get? Around here, it rains a lot…and I rarely lay flagstone on a very steep slope anyway. The stone dust stays put. You should get a prize for stumping me. Email me your address to claim your prize! Hi Devin, I am in pgh pa. Wondering what depth of gravel do we need under the flagstone? We ate planning about sq foot walkway.

And it may save our marriage. Approximately 4 inches of gravel beneath the flagstone. If you wish to have me over to help with the project, then you should send me an email and we can discuss the matter. We would like to install a flagstone patio and was wondering if we could do that right over the sand, or if we have to remove all of the sand uuuugh and put gravel down first?

The pool was there for approx. We live in upstate NY where winters are pretty brutal. I just want to do it right. Thanks in advance. A lot of it. Ants love sand. Sand with bricks or stone atop it is a big flashing neon invitation to ants who go marching a thousand by a thousand and they all go down to the ground, to excavate your patio!

You have your flagstone sitting right on sand and then they will undermine you, and within a few years you will have flagstone with big voids under them, and it will be a big big big problem.

Best of luck! If my advice is at all helpful to you, then please share some of my gallery photos on whatever social media you use. Wanted to put flagstones in so I excavated only to about 5 inches and laid 2 to 3 inches of crushed granite with the intention tamping and putting flagstones on top with something like larger crushed granite to fill the large joints. Before I could get the flagstones on top of the crushed granite base, we received years worth of rain in 2 weeks.

Any options other than rip everything out and dig deeper? Dig down inches deeper then I usually would. Mix it up good. The harder you tamp, the spongier it will become. You just end up vibrating the moisture upwards.

Keep building it up in lifts. First lift or two might be the driest soil you have on hand mixed with gravel. As you go up, lightl;y tamping at each lift,, it should be getting less and less spongy. After a time, come back and re-tamp, lightly, again. If rain comes in the meantime, you may need to tarp the scene. If you dig deep enough and tamp lightly enough, then you will not have to wait, but it will be solid enough when you get to the top. Okay, fine. This patio would butt right against the house and adjoining, existing concrete patio.

Anyway I got mostly through the excavation and my wife asked if I could use the same stone to cover a bit of concrete patio. So, from what I have read, this can be done, but the base layer for the patio must be really well compacted and aligned. Then screed the whole thing and lay stone using glue or mortar to hold the edges on the concrete. So my question really is can this be done? Is it wise? Having not seen the concrete pad, nor the stones you are using, I offer you my best take on the situation.

Your mileage may vary is what I mean to say. If the stones are cut stones, to uniform thickness, then they can probably just be laid flat on top of the concrete pad. Glue the outer ones and dry lay the inner may work…but if the inner stones have a wobble, even a minor one, you may just want to glue all the flagstones down.

Any exterior masonry adhesive will work. Make sure the patio and the stones are both fairly clean. EVEN BETTER solution, if the cut stones are large enough, and you have enough patience and ability, then you can possibly just lay the larger stones on the outside edge of the patio and lay them dry.

Lay them all dry. A mix of small medium and larger stones on the inner part of the patio, larger stones, ones that are too big to pop up under foot, go along the outer edge. No glue, no edging, no cement. I prefer 1. But, if they are saw cut and the foundation is screeded nice and perfect, then the stone can be made stable underfoot.

Just make sure foundation or bedding material is perfectly smooth, and gently mallet each stone into the bedding material.

Stones less that 1 square foot in surface area will be prone to not sitting stable. Polymer sand between irregular flagstones was a new concept for our installer about seven years ago in Prince Edward County Ontario Canada peninsula in the eastern end of Lake Ontario when we put in our patio.

We now have a mess of weeds and polymer sand left in the joints. We are in the country and weeds are a major problem. From reading your articles I am guessing I will have to remove the polymer sand filler and refill with screenings. My question is how deep should the area be between flagstone before adding the screening.

Short of redoing the entire patio which is a last resort, can we rescue the flagstone joints with screenings after removing the remaining sand? Still, a half inch screenings depth between your flagstones will work better than a half inch bed of poly sand, any day. Poly sand will require a greater depth—and will be more of a headache when it fails. So just clean out your polymeric sand from between the flagstones as planned, and sweep in screenings and hose down, let it air dry, then top off with more screenings and hose down again.

It might be fine, but it might not really succeed so well. Like I said, an inch deep is better, so you may want to spend some time to manually pull out some of the gravel on the higher spots.

Knees pads wear knee pads. Hire a local kid to spend a couple hours doing this simple, tedious task—or just gt into it yourself. Can I add small rocks of my own selection to my polymer-modified sand in between my flagstones? I do not recommend this. First of all, polymeric sand is prone to failing—as described in the above article, and many of the replies. Hose down, the add more stone dust to replace that which has settled. This method is a bit trickier and may need more maintenance, then the simple stone dust method.

Still, it is much better than using polymeric sand for your flagstone joints. We live in the northeast and had to tear out the old warped and cracked cemented flagstone patio before starting it over. I used the methods you described and just finished leveling all of the stones and have the grit used for leveling swept between the joints. I was going to cement a small barrier wall to keep the screenings from washing away under the stones on this side but was wondering what method you use to finish a slightly raised edge like this?

And the flagstones that come out to the edge, the stones on the edge, are thick—and set very stable. These flagstones at the edge of the patio, the stones touch at the joint. You know what I mean? The joint gets real tight, at the edge. Grit CAN still wash away.

And will. In my experience, the grit at the edge needed to be topped off a couple of times, but then stabilized. The owner had not topped them off because…it really caused no problem at all. Grit was swept in around and on top of the gravel, but a few chucks of gravel were in there too, to kind of slow down the washing away of grit.

My way is simple, patient stone placement. Some maintenance will be needed. If you go with cement…. Down the road however, the cement maintenance may end up being more of a headache, then dry stone maintenance. Hey, you chose to go DIY, so it will be a learning experience, way way or another! Hi Devin, This site is awesome! The patio was professionally built many years ago with a little interlock retaining wall around it, weed cloth, and limestone underneath.

I spoke to a very, very experienced mason friend of mine about this and he said it might work and it might not. In addition to that, one other big question I have is this: I saw another guy on a video who dealt with a a major crack in a concrete slab by using metal lathe to bind the concrete together before putting flagstone on top.

If so, could I do it just along the seams or would i put it on the whole square feet? Due to the intense volume of blog comments, calls, emails and texts that I have been receiving, I can walk you through any flagstone or patio repair or installation challenges that you may be facing.

I have an existing concrete cap that is sq feet. Using large Pennsylvania Fieldstone that I bought here in Atlanta area.

Originally, we thought about mortaring in joints between stones. Can I go back and top over the mini chip with screenings? Also, I get even better drainage, as water seeps down the mini chip grout lines. Any advice here? I love Flagstone!!! DIY flagstone consultations. Hi devin, How thick should my base be? GoING to use modified and top off with stone dust to level. I live in PA so you are aware of the climate. Is adding the Portland really necessary? Might create problems. The again, a ratio of one part cement to twelve parts screenings…um, it might be alright.

My feelings are that it will A be too rigid and crack. Or it might semi-solidify in the way that it is intended. IF it actually does that then I certainly foresee problems. My best recommendation is that clients hire me to do maybe a couple hours maintenance once a year—by no means is this nessesary, but I like my work to sparkle. The above quote is from this article. In conclusion, the system that I use, where screenings serve for both under the flagstone as the leveling agent, and for the flagstone joints too, works The cement notion might work alright…idk.

My bet, and I will put money on it, is that the system is much more of a maintenance hassle over the course of years—much like the poly-sand method.

Devin, Enjoy reading all your advice. I do get confused with the different materials. Making a square foot area as a walk way. Live in San Jose California. Some rain , rare freeze. It had weed block and 2 inch river rocks in place. River Rock a little wobbly under foot as a daily path.

I removed river Rock and old weed block. I have foot gray flagstone. Gaps are large inches. Was concerned about placing smaller rocks between flagstone- can get messy.

I could replace the river rocks between flagstone? The current dirt is quite compacted from the heavy river Rock resting on it, is inches of base gravel good? Sorry for the delayed response! My software had misidentified your message as spam, so I ignored it. My mistake! Anyway, You have a lot of questions. You seem to need help, from square one. I could help you with a phone consultation Or I could just direct you to read more of my blog posts.

Hi Devin, I have a question for you about screenings. They tried using Techniseal polymeric sand, but it would not set. In some areas it remained spongy and anything heavy or sharp would break through.

Is that okay?? Because we have irregular shaped stones, some of the joints are quite large. Can you help, give advice, tell me all my worries are for naught, anything? Thank you! Site conditions, how wide the joints actually are, how big the joints are in relation to the flagstones, and other site specific factors would have a bearing on that. Usually, I end up spending a day or so re-fitting the stones and making them look like a skilled flagstone guy did them. If you still need more flagstone or hardscape related advice, you can email me photos and set up a 1 on 1 phone consultation.

Sure wish I had read this 3 years ago before someone convinced me that they could relay my flagstone walk and put material between the stones so it would not be a trip hazard. It was only 1 year and it was falling apart. Sorry to hear of your flagstone troubles! My recommendation is that you fit them flagstones a bit tighter, 2 inches or so will be alright, and then sweep in stone dust.

Flagstone responds much better, to a happy jobsite. The consistency should be like a stiff applesauce, not runny applesauce. If it's hot, windy and sunny, only mix as much as you can use in 30 minutes.

Do not add water to the mortar if it starts to get stiff. Cool weather is your friend but cold weather is indeed your enemy as you attempt to finish this job. If the mortar had its choice of weather conditions, it would undoubtedly tell us to install it on days when the air temperature was in the midsF with overcast skies. A nighttime low temperature of 40F would be ideal. Believe it or not, sunny hot, dry or breezy weather are not great conditions for working with mortar and concrete.

I would not install any flagstone or brick if the air temperature is forecast to drop below 28F for 48 hours after you install them. You can help yourself immensely by preheating the materials you will be working with. If at all possible, keep the sand, cement, and hydrated lime indoors at room temperature and only bring it outdoors to mix it. Use very warm or hot water to mix the mortar. Try to heat the brick or flagstone as well although this may be far more difficult to accomplish. After you lay the flagstone or brick, cover them as soon as possible with waterproof insulating blankets.

These can be rented at tool rental businesses. The mortar actually creates a small amount of heat as it cures and hardens, and if retained within the masonry instead of released to outer space, it helps the mortar get stronger faster. Keep the masonry covered with the blankets for at least 48 hours if possible.

As the air temperature drops so does the temperature of materials stored outdoors and the actual concrete to which the flagstone and brick will be attached.

These cold temps radically affect the chemical reaction of hydration that starts the moment water is added to the powdered cement and hydrated lime. Hydration is the reaction that turns the powdered cement and lime into actual microscopic cement paste crystals that interlock the sand particles together.

To resist the expansion forces of freezing temperatures, a certain amount of crystals need to form. The way to accomplish this is to fool the mortar into thinking it is 55F or higher.

You do just that by preheating all of the ingredients and by storing all of that heat as you do each night when you sleep under blankets or a comforter. Sign up to my newsletter to receive expert advice for your home! Complete the form below and each week you'll get:.