I’m used to working with wood, not stone — so pardon my ignorance and the length of this post.
I want to fix up our old patio and walkway which is clearly in need of TLC. The situation:
1. Original patio made of large, irregular 1-3″ flagstones set on a concrete base with approximately 3/4″ concrete mortar joints located in N Georgia (occasional freeze).
2. Current problem is with the mortar joints, in general, rather than the stones themselves. More than half the grout joints have either completely failed (missing or replaced by dirt) or are in the process of failing (come apart with air hose or light touch). The stones, with the exception of several small fillers, are perfectly set, level and stable. However, while the stones sit perfectly, some of them are actually unbonded with the concrete below — and will lift if raised (as I clean out the grout joints).
3. Original solution: I envisioned this as a large regrouting job — but am concerned I may be missing the boat regarding the unbonded stones.
For regrouting, I am cleaning all the joints with compressed air and a bit of persuasion from a screwdriver to clean out old mortar, dirt, etc. It’s not hard to clean the joints down to the solid concrete base — in general without disturbing the stones. I plan to use a 50/50 cement/sand mixture (bag applied) to regrout.
4. Question about stone setting: Assuming my regrouting approach is correct, what should I do about unbonded stones? I tried removing and resetting one of the obviously loose stones, and could not obtain the original level, stable set. Under the loose stone was dirt and bits of deteriorated mortar, which shifted after resetting and killed the fit. Cleaning out the loose stuff only made things worse. So,
a. With obviously loose stones, do I need to reset them — and if so how? Is new grout enough to hold them in place?
b. With unbonded, but well set stones — do I just grout and leave them alone?
5. Finally, the question I’m afraid to ask: Is this really not a manageable regrouting project, but rather a massive rebuilding and resetting of the entire patio and walkway?
I appreciate you taking the time to read all this. I look forward to any responses.
Ken