Question
Hello. We have an approximately 30 year old 22X16 concrete slab patio which has several cracks running from a drilled hole for an umbrella stand (which was not put in by us) the length of the slab. Each section of the slab is therefore unlevel due to the soil erosion under the slab by 1-2 inches. My husband thinks that we can mudjack the whole thing and then use it as a base for a new flagstone patio. Is this possible? If not, once we broke up and disposed of the concrete, if we wanted to install some raised vegetable beds, would we need to remove the probable 3-4 in of substrate base for adequate soil for the beds? Thanks so much and any ideas are very welcome!

Answer
First, I'm not personally experienced with Mudjacking but from what I understand about the process, assuming there are not significant underlying problems like water running below the patio, then it might work well.

As for the second part of your question. Without knowing the composition of the soil below the existing patio it is impossible to advise you. In many cases patios are not poured on any kind of prepared soil or sub-base. However sometimes they are. If you find gravel, specially if it is compacted you should remove it. If it is loose gravel and there is not more than a few inches it may be ok, assuming you are coming back with a foot or more of good garden soil over top.

Best of luck.


Sean J Murphy, LA,ISA, LEED AP
Please check out my blogs and articles on landscape topics like this on my websites.
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