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

Hard to tell from the photo, is it the footer for the wall? ______________

It doesn't, necessarily. If hosing and brushing does the job, fine; if not, HCl. What you want is for the old concrete surface to be clean enough for the mortar you will use to lay the stone to bond well to it.

The water is coming from the little fish pond behind the concrete wall. I never noticed the seepage until now. I wonder if my digging disturbed something.

I don't know what a 'footer' is; but it was almost certainly built when the wall was built so it must be what I'd call the 'foundation' for the wall.

You should be able to get some rubber/vinly paint sort of stuff they use on pools. Maybe even a vinyl liner for the pond.

I was thinking of patching it up with 'hydraulic cement' but if painting it with special paint works - that's what I'll do.

Only later. I haven't had a chance to work on it since Monday unfortunately - so there's no progress to report.

The bags of mortar & concrete are getting wet by the day being outside in the dew so I'd better hurry.

If you have a crack big enough to put the cement into, do that first. If they're tiny cracks (likely) then hydraulic cement won't help.

Put a tarp over them or put them in garbage bags.

Status Update:

I've cut all but the final middle keystone.

Tomorrow I put the mortar down.

I have two questions about that - but I'll open a separate thread for each since it's not the original topic of this thread.

Here's a picture as I closed up shop just after the sun set tonight:

UPDATE: It took way longer than I thought it would ... but here is the cut flagstone laid out (except for the one middle stone) ... ready for mortar tomorrow.

Left half:

:)

Chuck, I'm no expert on this but is it safe to build up mortar 2" thick? Is this going to be outside with freezing temps? I was wondering if it's better to use some kind of cement that can be about

I don't know either! (I've never done any of this before.)

I 'assume' mortar is as strong as concrete (which is basically mortar plus aggregate if I understand it correctly). Does the aggregate give strength or does it just give it bulk for cost reasons?

As for freezing, it 'can' get to freezing out here - but rarely does. We get a dusting of snow, for example, once every few years. Generally it drops to freezing about 5 times a year, and always at night only. By morning it's warmed up and melted.

One reason I need depth is the stones vary in thickness, even though I tried (I really tried hard) to keep the thickness variation down to a minimum.

Another reason I 'want' depth is that there is the high spot at the left- most side that is a ledge about two inches above the rest of the step. I don't have to meet the two evenly. I 'could' have a small 1-inch step.

The problem is hard to describe so here's a picture of the small ledge that has two flagstones in it. I was planning on bringing up all 20 flagstones to that same level to eliminate the ledge.

I have no idea how deeply the footer goes into the ground.

For better or worse, I've already set the first two stones to the upper level (which previously existed, at a 90degree right angle to the shelf that I am tiling):

That question brings up a point I had not mentioned prior.

Since I had dug down to the footer (which was 2 inches under the existing lawn), I now have the problem of the lawn being two inches higher than the shelf (if I don't raise the shelf).

Drat.

For better or worse, here's the final result, set in concrete & mortar:

I picked up a small cultivator from Lowes today. I will use that to dig up the lawn because it's currently HIGHER than the level of the sandstone shelf.

Here's the curing process ...

:)