Im planning to redo our patio. It's currently field stone in concrete. And I want to lay flagstone. It's uneven and has cracked at a few places. The concrete base is about 5" thick. It hasn't cracked anymore since we've moved in. I was going to expand the patio but have decided I'll keep it the same size and then add a deck extension. I had a landscape company come out last spring and they said they would keep the base and take out the high spots (some large field stone in it) and then put a base layer to lay the flagstone in. They told me a price and I about passed out. I really dont think they wanted the job. They do huge projects at million dollar homes. I'm hoping I can use the current base like they said after I take out the high spots. What material and depth are recommended to lay the flagstone? Ive seen "paver panels" that are used by some, are they legit? Im in south central PA, so we do get freeze thaw patterns.
I'm no pro here but have done a couple paver/stepping stone jobs. Usually id use 2" of sand over a solid rock/gravel base. That way you can sink the flagstone into it and make the top level. Here's a quick internet search article i found. Preparing the Base for a Flagstone Walkway Since you already have a concreat base that hasn't shifted or moved for awhile it might be fine to build on it for the long term. How much room is between the current patio and any door thresholds? Then figure your flagstone thickness. You probably don't want more than a 2" base of sand. Could probably get away with 1". Just depends how thick some of the stones are vs the high spots in the current patio.
Here we dug out the sod and filled the trench with about 2" of crushed rock. Smooth it out decent and packed it down good. Then about 1" of clean sand. No stones of any kind. Smooth/screed the sand with a 4' level. Then set the pavers and level them. Obviously your project is a little different but the basics are similar.
Thanks Jeffrey Svoboda . I've read several articles and watched tons of videos but haven't seen any where they have used a previous concrete pad as a base. At least not for dry laying pavers/ flagstone. Here a couple pics.
Yea I'm not sure sand would work good as a base for your new stones on top of that pad. Likely would hold water in spots. Plus it looks pretty enclosed in like water can't drain out all sides or at least 3 sides away from the house. I would think about laying your new stone down like tile. Mix up some concrete and glob on the back of the new stone. Lay new stone down on old stone and mush it down. This way will be time consuming to figure out how much concete needs to go between the bottom layer and new top layer. Then once the whole top layer is set, mix of a thin slurry of concrete to pour between all the new flagstone. That way your new patio is sealed up. The key would be to keep it sealed cause any water that makes its way between the two layers can freeze and start breaking up the new layer. This can also happen with a sand base over the existing concrete if the current pad isn't sloped good for drainage. Obviously this is all after you make the current slab as flat as possible. The best thing to do would be to break it all out. Put in a good drain system. Then build up a good base for you patio. All the water/moisture will be carried away so nothing can heave when it freezes. Hopefully that all kinda makes sense.
Make any headway on this project? I’ll agree with Jeffrey. No sand on top. Here in New England we’ve gotten away from using sand altogether unless you ask Home Depot We use stone dust for a topping layer. Doesn’t shift around underneath like sand does. But that’s a different story and I wouldn’t recommend stone dust for your application either. I would knock down any high spots and run concrete/cement over the top to even it out, get your pitches correct. Then decide on what goes on top. Dry laid brick would hide any more cracking and movement that may occur. I suspect it will still occur seeing as it’s happened already. Probably more of a seasonal frost issue than a bad base so it will occur, just less. But because there is a base with poor to zero drainage you’d want some sort of panel to do the actual support even after leveling out with cement. I’ve never worked with the panels. They are a possibility. I know I’ve seen some that are designed to hold brick in a pattern. More expensive of course but easy to use. They didn’t have such things when I was doing residential masonry. Everything was old school or go home LOL if you really want Bluestone they could be hand laid in a cementitious sand mix. Just Portland cement and sand. No lime, no aggregate. Did plenty of those back in the day. That’s real,old school stuff. Wouldn’t need to pour anything first. Just get your finished heights and lay. Need a cement or mortar mixer. Wouldn’t want to mix all that by hand. You may be laying tight near the high spots and have 3” of cement under the lows spots. It’s all good, won’t matter. You make a paste with Portland and water to brush on the bottom of stone before laying.
Project is stuck in neutral. Actually, I dont even know if engine has started. Once I had the high sections knocked down and heights finished, you just lay flagstone with the paste right on top of what's there? No other cement base or panel?
no you need something to level everything out. Just instead of pouring an entire pad all at once and then mortaring on top you lay them in a sand mix (Portland cement and sand) The paste is just the old school way of bonding the stone to the sand mix. Have to call it sand mix. It’s technically not cement and not concrete. Basically the same as mortar but without lime at all. More strength, less cracking, less shrinkage. Many old patios such as yours were built with this method. Basically just toss down 3” of sand mix and lay the stones right in it as you go. No building a concrete pad. Because you already have a pad thickness isn’t an issue. The problem with going with just sand or stone dust and dry laid brick/stone is you have an impermeable barrier at ground level. Water will sit under there and it’ll always be mushy. Sand when soaked has a tendency to migrate towards any low spots just like water. Just a little slower
Ok. It’s still a lot of work. Don’t let me kid ya. One nice thing is you can go at your own pace. You wanna lay one stone a day you can. If the engine ever starts and you’d like a better road map just give a holler.
