Background:
I live in the midwest U.S. and I have a rectangular concrete patio that's about 400 sq ft (see attached picture). The original concrete patio is about 18 years old, and it was extended about 10 years ago. The concrete is in very good shape. I would like to make my patio look something like what is shown in the attached last picture – flagstone with white grouts. I talked to some landscaping companies to see if it is possible for them to install flagstone on top of the concrete and also to extend the patio with flagstone by about 100 sq ft to an area that's currently covered in grass. One company gave me a reasonable quote (~$8.5K) to install Pennsylvania slate slabs on top of the concrete with 1/2" mortar + the 100 sq ft extension. Two of the companies refused to take on the job. They recommended that I either tear out the existing concrete first or that I talk to a mason.
Questions:
- Is it ok to install flagstone / Pennsylvania slate slabs on top of existing concrete without causing issues in the long run? Or is it a much safer option to remove the concrete first before installing the new flagstone?
- The junction between the old and new concrete is not perfectly level with each other (see attached picture). If it is ok to install flagstone on top of concrete, I am thinking about getting an angle grinder to make this junction more level with each other. Is this a recommended path?
- Is this a job that landscaping companies should do or are masons better suited for this job?
by xtonus95x
8 Comments
I mean I won’t stop you
No, that will result in cracked and broken stone. Remove the concrete, add limestone crush, tamp it, place flagstone, use quality 4″ polymerization sand. Do it right.
You can lay flagstone over existing concrete. The issue, and the reason I think you’re getting pushback, is because if we don’t install the concrete we can’t warranty the work. I’ve taken out concrete slabs that are 2 in thick and some that are 8 in thick, and there’s no way to tell what it’s like in the middle of the slab.
The lip of the new slab sticking up is really the issue for me. We would want to pitch the flagstone so it all slopes away from the house. If that slab is sitting a little higher, you’re going to have a heck of a mortar bed to be able to make that happen. Plus, if the new slab wasn’t pinned in to the old slab, you’re pretty much guaranteed to get a big settlement crack there that telegraphs it’s way through to the face of the flagstone.
Ultimately spend your money how you want, but if that concrete is in good shape I’d keep it and spend that money elsewhere.
We painted our patio with a stencil and the result is really nice. Downside is it’s a bit more slick when wet, but it looks awesome. And it was very DIY. I’m guessing there are other applications that would be more professional and give you an aesthetic you’re looking for.
If it were me, I’d spend that $8k on landscaping, other paths around the yard, a pergola, outdoor furniture, a hot tub, or whatever else comes to mind. That flagstone look is really beautiful so I get it tho if you just want to make the space your own.
What is it you don.t like about the concrete? What do you want from the flagstone… a more natural kind of look? If so, look into staining or painting options. Is this home new to you? Do you just have a pile of money you feel like spending?
I like flagstone too but i opted for concrete for my patio. Much less work and money, and less long term maintenance. My quotes were 2-3x the cost of concrete.
White grout will look dirty pretty fast, and will eventually break up and weeds will grow in it.
With concrete in such good shape invest in something else that will enhance your space in the aesthetics and use you like.
The risk is as others have pointed out that the base is not compromised and that expansion/contraction and movement between the newer pad and existing pad would move differently and thus telegraph through to the flagstone layer.
A concrete pad would be a great base for a stone/paver patio if the base is compacted and the concrete was poured correctly without voids and is no longer settling. Those are the risks the hardscaping contractors would not be willing to take on since they did not install the pad themselves.
This is 10000% something I would tackle as Diy however and assume the risks. I myself would have a hard time paying a contractor at that price point knowing that there is a real possibility the flagstone would look worse than my concrete pad if those issues arise. If that first company that gave you a quote of $20 per sq ft will back it up with a warranty of say 3-5 years and you specifically tell them your concerns then go for it.
Else it would be advisable to budget for tearing out the existing pad if having a contractor take this job on.
My opinion which counts the least here is if there is any level of return on investment and this is not your forever home then I would suggest looking elsewhere to spend money tearing up a concrete pad in great shape that serves the same purpose as the flagstone patio. It’s purely aesthetics but provides no additional value add to the property.
Leave well enough alone! I like thw concrete look better.
I hired a hardscaping/landscaping company to put in a paver patio and they demoed the existing concrete for free as long as we were replacing it with something (the pavers) from them. When I was researching quotes all the companies agreed to this actually. Something to keep it mind