What is UNDER flagstones on concrete? How do you keep the tops level? (Pictures)

[Chuck Banshee]

This weekend I will finally start cutting & cementing the flagstone on the walkway (see four photos below for detail) and three questions arose:

Q1: What is UNDER these flagstones on cement (are they glued?) Q2: If you glue them, how do you keep the tops evenly flat? Q3: Since the step width varies by 3 inches, can it take a 3" overhang?

Here is a picture of the concrete base that I plan on putting flagstone. Notice the base starts at 18 inches but eventually narrows to 15". Can a 3" overhang (maximum) be supported with just the packed soil below?

Here is a picture of that same base, only further away to give you a better idea of the problem set: Here is a picture of the enigma. What is UNDER these existing flagstones? Are they simply GLUED on? (There seems to be NOTHING under them!) Here is another picture of the existing flagstones in the water feature. They appear to have NOTHING under them. Can that be? The reason these three question matter is: a) I need to lay the flagstone on the concrete and I don't know if I glue them on or if I just grout the spaces between each stone. b) If I glue them on, I don't know how to keep the tops flat since each stone is slightly different in thickness. c) Even though the base starts at 18" wide, it narrows to 15" wide but I would want the stone to stay the same width.

Any advice is always appreciated!

[Chuck Banshee]

Here is a view further out showing the entire construction zone:

The problem I'm having trouble figuring out how to solve is how to put flagstone along the foundation where the front side is in dirt (with water pipes unexpectedly popping out when I dug the path) - and the other side having a 15" to 18" concrete ledge to put the flagstones upon.

How would you suggest I lay the flagstones so that one can walk along the side of the foundation?

[dadiOH]

Glued? No. One sets them in mortar.

Mortar bed thick enough to let you level the top surfaces. Ever watch a block layer? Toss out mortar bed, set block, tap block to level with neighboring block, scrape off ooze out.

If your stones vary considerably in thickness, dry lay them first so you can see how much mortar you need under the thinnest. The mortar needs to be stiff enough to support them; you can cheat a bit if need be by using a couple of pebbles or whatever.

Not unsupported.

Maybe. Best to just even up the slab...dig out, add concrete. If the patch area is very long, add some dowels...drill horizontally into existing slab, insert dowels cut from rebar, pour your patch. _______________________

Regarding "How would you suggest I lay the flagstones so that one can walk along the side of the foundation?"...

You really only have two options: raise the walkway or lower the pipes. ______________________

People *do* set flags/bricks/pavers directly on the ground. People do lots of things and then wonder why what they did disintegrates. If you want a decent job, you must...

1. Remove the sod/plants/soil to a depth sufficient to accomodate 3" of compacted bed material + 1" of bedding sand + the thickness of the pavers.
2. Add bedding material. Around here, they use crushed concrete. Works well, good mix of fines and larger pieces. To get 3" compacted of that, one needs about 4 1/2". The material used varies depending on where you are. The bedding material is dumped in then raked out to flatten and provide desired slope for drainage.
3. Compact

1. Lay sand, rake and even up. The purpose of the sand is to provide a base into which irregular surfaces can settle. If what you are laying has even surfaces, you don't really need the sand *IF* the coarser bedding material has a decent surface.

2. Lay the stone

1. Compact again (to settle stone into sand)

2. Do the joints. _____________________

You might want to consider having at least the prep work done by pros. We did 1700 sq.ft. of brick in our courtyard a couple of years ago. The 3-4 man crew of Brazilians did all the prep, layed the bricks and sanded in the joints in two days. A fair amount of cutting too. The cost, exclusive of bricks but including all other materials, worked out to be $2.50 sq.ft. A bargain.

[trader4]

Some general comments:

1 - From the pic of where the walkway is I don't understand all the fuss in the other thread about protecting the PVC pipes against the wall. Looks like a perfect spot for some flowers, shrubs with mulch covering the pipes.

2 - As to what is holding the existing flagstones, you have what appears to be some of the material that oozed out around the edge in one pic. Chip a piece off and look at it. Normally you'd expect it to be in thinset or similar, but it could be some kind of adhesive.

3 - For the new walkway you don't need any of that. You need a stabilized base, which usually means removing any soft earth that is there, replacing it with base material which could be crushed rock or gravel. Then you put about an inch of sand or stone dust and use that to bed the flagstone. I'd put down metal edging first along the sides to give it a clean seperation from the grass.

[Evan]

You are planning on setting the pavers on the footing for whatever that stepped planting bed with the "water feature" in it ?

You need to know what level you will be setting the pavers at and then either add concrete to the footing so it gets closer to the finished level so you can use bedding mortar to attach the stones, or you can use pack (stonedust) material -- not sand... You would only be creating a situation where water would be likely to collect and pool under the stones at the footing which could do all sorts of terrible things over the passage of time...

Others here have said enough explaining your question about how the other flagstones are attached...

You need to rent a bigger saw, a gasoline powered cut off saw with a diamond blade which uses water to keep the dust down... You have so many cuts coming up and that small little circular saw will not last through all of them even with a diamond blade...

Sorry to say this to you but this project looks like it is adding up to something that is well beyond your skill level given the questions you have been asking about it...

Hire a professional stone mason to do it for you...

~~ Evan

[gfretwell]

I have a tad over 2300 square feet of gold quartzite flagstone around my house, all set over concrete. It started as a small lanai and then a pool deck and a number of additions to that. We used Type S mortar to set them with a bit of latex additive in the mix to make things stick better

The first step is doing the puzzle. You start dry laying the stone just to figure out what the pattern is going to be. This is probably the most time consuming part but it is not time sensitive. We usually played with the stone for a week or so in a given new area before we were happy.

If you are doing steps or some area that is critical on stone size, do that first while you still have a lot of stone to choose from. That usually eliminates having to do much cutting. We never really cut any stone. That quartzite granite is real hard to cut anyway.

Once you are happy with the layout, lay down a thick mud bed of the type S mortar and set the stone. Over the years we have developed a couple of different techniques for doing this but the best way seems to be to lay them and wipe the tops clean at the same time. You really start to get an eye for getting them level. At first we used a 4' 2x4 as a guide. Like another poster said, be sure the final level is high enough to accommodate the thickest stone.

Start in the far corner and work out to where you want to stop. Once the stone is set, any glaze of mortar on the stone will come off with a pressure cleaner. It does get a lot better with time. They will always look dirty when you first do it but the mortar glaze goes away.

Don't mind the snake

[DanG]

Chuck, you have more loam to remove. Get a healthy load of "red select" or whatever compactible select fill is normally available in your area. Set up an edge form on the outboard edge of the proposed walk. It will work to grade to a chalk line at the foundation, but it will be easier to set a grade screed there also. Install, grade, and compact the fill. You have no requirement to follow the paint line that is established on your foundation, the walk can follow the layout of the top cap of the foundation wall which will allow you to go over the pipes with the fill, raise the control box to the stone grade, and have your stone walkway. If you ever need to work on the pipes, everything is fairly easy to remove.

[Chuck Banshee]

You're right!

It took me almost the entire day (Saturday) to do this step!

It's bad enough that I mostly have small well broken pieces to deal with.

Luckily, both the steel diamond saw and the brown-material masonry saw easily cut the flagstone (although the diamond saw seems to cut twice as fast). Both dust up terribly!

Here is a picture of the stones very roughly laid out (without any cutting).

The puzzle is driving me CRAZY! (being ocd)

In addition ... I'm not sure if you cut the last edge (the outside) edge last or if I cut all the edges before setting them in concrete.

Either way, my plan is to cut them to fit today.

[Chuck Banshee]

For half the walkway, there is already a concrete (rough surface) foundation. That's the half I'm doing first (because it's easier).

Here is a picture of the step up I tried as the very first effort.

It took 1 bag of mortar (50#) and one gallon of water. No sand. No rocks.

In hindsight, it wasn't enough to raise the level the required two inches ... so I have to start over again today.

I did cut the rocks to fit almost seamlessly. The cutting is the easy part. The hard part is figuring out how to glue it all together.

[Chuck Banshee]

I think I used the wrong stuff.

What I used was pure mortar (no rock, no sand).

The entire bag barely brought this small spot up to the level of a single two-by-four set flat on the ground!

[Evan]

No you have to realize that when you are laying a mortar bed to raise something up you have to let it set and it does take quite a bit of material to fill what you think looks like a small volume of space...

When you have a flat, leveled area that is close in elevation to where you want your finished flagstone whatever to be at you would then use a shallow bedding coat of mortar to lay the stones in... If you set the pavers on the wet 2" of mortar they would sink unevenly into the wet mortar depending on how heavy they were and the mortar bed would take forever to cure...

~~ Evan

[Tony Miklos]

Why would it take longer for the mortar to cure?

[dadiOH]

There is no such thing as mortar without sand. Mortar is cement, sand and some lime. Add aggregate and it becomes concrete.

[krw]

Use a wet saw. The water keeps the dust down considerably. BTW, why are you cutting them at all?

[gfretwell]

We always get the dry fit first. You really want a natural edge showing and cut the parts that will be in the mud. If you do end up with a cut edge, use a brick hammer to chip up the edge a little to get the natural look back. The quartzite granite we use is so hard it just laughs at a diamond blade. You can get through it but it is painfully slow. The fiber blades just smoke and wear away.

[gfretwell]

I would use bagged concrete for that,. Float it pout level and brush it when it is set "finger dent" hard with a corn broom to get a good surface for the mortar to bite.

[Chuck Banshee]

Today I thought I'd finish the job (my first ever with concrete and my first ever with flagstones) - but - alas - I only got six of about 18 flagstones cut. Sigh.

And, while laying them out uncut was certainly a good idea, it turns out that I just couldn't fully process mentally the myriad permutations and combinations inherent in that process. So, for example, three stones I 'thought' would fit perfectly, didn't fit.

So I had to remove them all anyway and start over (many times). Here's a picture of just one permutation of the uncut flagstones:

I also learned that there's a LOT of leaning over with BOTH hands on the heavy stones and you can't get around that (because there is a wall in front of you). The best you can do is put a towel on your head to protect it as you lean against the wall and use both hands on the stone.

Here's a picture of the cut stones.

If anyone knows whether that last (outside) edge cut is supposed to be cut BEFORE or AFTER the flagstones are laid in concrete, it would be helpful if you can let me know (before I make the final call on that).

Thanks for all your help!

- The hardest part is the dry jigsaw-puzzle and the cutting choices

- Given very few usable stones to work with doesn't help the matter

- Tomorrow, I hope, to finish the dry cutting - and then mortar them in!

[Chuck Banshee]

While that's great advice, I don't have a helper to spray a hose on the diamond saw, nor a wet saw apparatus - so - for this (my first concrete & flagstone job) - it's going to have to be done dusty! :)

And, I understand why many are saying NOT to cut the stones, but this picture should show why I must cut all the edges of the stones to match the existing water feature:

BTW, I noticed water seeping out of the concrete of the water feature (see the picture for details).

Is that water leak easily repairable while I'm working on this project?

[Chuck Banshee]

I appreciably stand corrected (I didn't ADD any more sand). :)

BTW, I've learned a bunch of 'little' things:

* * * * * *

[Chuck Banshee]

I appreciably stand corrected (I didn't ADD any more sand). :) I've never mixed cement/mortar before so this is a first for me. Tomorrow I hope to finish the job so I'll go to Home Depot to pick up about ten bags of mortar, concrete, sand, and rock.

BTW, I've learned a bunch of 'little' things so far:

• Flip the ROUGH side down & the GOOD side up on all stones FIRST

• Then SORT the stones by large, medium, & small (I put them on shelves)

• Then SORT AGAIN, this time by square, rectangular, & triangular

• Once they're sorted, lay the stones on the walkway as best you can

• It helps greatly to put a thin board against the wall to give yourself room to judge where to cut the top line (against the wall)

• Where funny shapes arise, it helps to put an entire stone on top of them

• It helps to have something soft (like a towel) to pad your head as you're ALWAYS LEANING OVER with both hands on the stone so your head is the third leg of the tripod (your knees being the other two legs)

• It helps to put a one-inch board between the cuts of the stone to get an idea of the finished fit

• At some points, I just said TO HECK WITH IT and started cutting - at least putting a definite edge on a stone eliminated one variable - things went easier when I did that!

• It takes a TON MORE MORTAR than you think it will!

• Cutting the sandstone is very easy with a 7" circular saw with a diamond blade. The composite blade didn't work as well.

• However, it's nearly impossible to REMOVE the blade! A normal wood saw has teeth you can jam a stick of wood in to immobilize the shaft. How DO you guys immobilize the shaft when using these composite blades?

PS: The mud had a benefit of showing exactly where the bobcat visited my construction site last night!