forgot the pictures

Describe the construction of the existing patio in greater detail. What is the base? How thick is the base and how thick the "slabs"? What kind of pavers are you talking about using ... normal thickness or thin? On sand or mortared? We can't see much of the patio; is it in good shape ... smooth and pitched correctly to drain?

It may be that if the existing pavers have shifted over time, the new overlay may not be equally supported, and may crack?
That is the only possibility I can imagine may be the reason for their first doubts.
Test it - get a good, straight edged plank, and lay it across the patio - all directions and angles.
If you or a helper can see daylight between existing patio and the straight edged plank, then future cracking is a definite possibility. H T H

We don't know much about the construction of the existing patio.
it's probably 20 years old and in good shape, pitched correctly.
From what we can see, it seems like it's done on a compact sand base with base rocks
The slabs are about 3 inch thick
In discussion with contractors, they suggest mortar with flagstone or slate tile
and sand with regular pavers. What should we go with?

btw, the idea of paving over was suggested by the first company we talked to long time ago. they said "it's in good shape". their overall quote was way too high so we didn't go back to discuss further.

uploading more photos, hope it helps clarify

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Since the existing patio is on a granular base (as opposed to solid concrete) I would absolutely, positively NOT consider any mortared work on top of it. The reason is that the earth is a flexible surface. Though it moves so slowly you can't see it, it is doing it nevertheless. If you were to mortar flagstone or thin brick on top of it, this work would effectively be only as thick as the mortar that glued it on ... 1/2" maybe (?) It wouldn't be thick enough to support itself as the earth underneath shifts. If you're going to mortar something on top, you need a 4" solid concrete, driveway-like base (3 1/2" actual) that will not flex at all.

But you could go over it with regular thickness pavers on sand IF you insulate the two layers with an inch of sand. (This is predicated on knowing that the existing base is of SOLID compacted material. Since it's been there a good while, its present shape is a good indicator of how solid the base is.) I would go so far as to say that if the present patio was perfect condition -- smooth, of perfect grade, and all slab joints perfectly matched -- you could go over it without the sand insulation. But it's not likely that it's that perfect. If you go over it, one thing you'll need to pre-plan carefully is the finish grade. It looks like your grade might end up being too high. I don't know what all the holes at the foundation are for, but they're probably not wanting to be blocked. If you need a lower grade, sell all those slabs on craigslist (someone would probably love to have them ... they look like step treads, BTW) and build directly onto your already existing base.

It's funny, I'm not normally conservative and risk averse but apparently I am when it comes to construction. 1" of bedding sand isn't going to insulate the paver surface from any movement of the base because the bedding layer isn't there to hide the sins of the base layer, even in a standard ICPI-spec installation. Any differential movement of those slabs will telegraph up and be visible in the paver patio.

Could it be done and no problems manifest themselves? Sure, but the only scenario in which I would feel comfortable doing this would be if it were my patio and I was scrambling to get it together for a family reunion, because in the event there's a problem I can easily get guys in to pull up the pavers and remove the sand, No way would I want to pay for this.

Yard's dead on with the masonry. Doing pavers over this is probably bad. Doing masonry over this is 100% guaranteed to be bad.

Marcinde, I'm not disagreeing with you that any movement of the base will become evident at the surface of new work, but the OP is saying the base is stable and has been there for 20 years. Pictures show it looking pretty good actually. Seeing more of the existing patio -- and that it is in good shape --makes me wonder WHY the OP wants to cover it up with something else...?? It looks now that it could be made quite nice. What's wrong with it that we can't see? MNA, why are you wanting to cover up this patio?

As a DIY project I'd say the odds are in the OP's favor, so go for it. Worst case scenario you're removing a re-laying some pavers and slopping around some bedding sand. But if you're hiring a professional contractor to do the job, how much is it REALLY adding to the cost of the job to demo the existing and put in a proper base? My go-to masonry contractor and his boys would have that demo'd and excavated in a day and be laying pavers by the end of day 2.

We are in the process of getting bids for a new stamped concrete area and refurbishing an original concrete patio and sidewalk. The sidewalk has a couple large wooden strips in it, and the contractor who bid last night was shaking his head.

He said he can get rid of the wood, fill the concrete and do some kind of fiberglass fix over it, OR he can just rip out the concrete, put in a new sidewalk, and use outside tile to spiff up the patio. Tile? Like the tile in the house over the slab? Yep!

So I am all excited, and mention I'm going to post this suggestion for you! He said, "whoa!" Be sure you tell them to seek a contractor who has done this before and knows how to do it. Not all concrete contractors are equal!

So I'm suggesting you consider an option of outdoor tile, instead of pavers, but warning you to find a knowledgeable and experienced contractor who can show examples of his work, and who can get rid of the wood, replace with concrete and use that fiberglass type filler to smooth the surface between your cement sections.

There are so many new products out there, and it helps to get many bids because not every contractor knows about all the newest improvements in their industry.

Good luck! Show pictures of your completed project!

Here is a link that might be useful: Some inspiration for you

This post was edited by desertdance on Tue, Feb 25, 14 at 10:12