I originally posted in General Discussion with no luck — hope it makes more sense to post in this forum.
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
Replies
Fortunately, you have a concrete slab. This is good. Hopefully you have a slab 4" thick. At least 3 1/2". Any less, and the slab may crack, causing cracks in the mortar joints.
It is unclear to me whether you have a setting bed, or simply 3/4" mortar joints. If you don't have a setting bed, you need one. The bed should be 3/4" thick. If you have a setting bed, but it's to thin, you might have to start over.
If you do have a setting bed, perhaps you didn't wait long enough before filling in the joints. You should have waited two days for the mortar to set. If you didn't, you may also have to start over.
The problem may also lye in the mortar mix. Whether it does or not, you might try a different mortar mix. For the bed (if you decide you need to lay one) try a mixture of 25% portland cement, 75% course sand. Make sure it's not too dry. It should be just moist enough for the stones to float into place.
Wait a couple days for the bed to set. Then fill the joints with a mixture of 25% portland cement, 75% medium sand.
If most all the stones are well set in a 3/4" setting bed, and your setting them on top a slab approximately 4" thick, you might simply try re-grouting with the afore mentioned mixture for filling in the joints. Make sure you do so on a clean surface, completely free of dirt.
Edited 11/18/2005 6:43 pm ET by JourneymanCarpenterT
Thanks for the helpful responses.I aplogize that in my long-winded original post I left out critical information. The patio/walk I am describing was built 30+ years ago by someone else and probably partially regrouted (again by someone else) over the years.I am trying to renovate the orignal work and need to decide whether regrout/repoint alone will do the trick?After reviewing the very helpful recommened site, I can fill in the details you requested:1. Crazy stone set on 4" concrete bed and (at least) 3/4" setting bed. As best as I can tell, both the concrete and setting bed are in good condition. (see below for a clarification)2. Grout joints failed -- generally gone (filled with dirt) or turn to dust with cleaning.3. Stones remain perfectly set (i.e. no movement) in the setting bed -- but are NOT adhered to the setting bed. This is only apparent after cleaning out the bad grout and lifting the stones.4. When I lift a perfectly set stone, there is fine debris beneath the stone -- which I assume is a partial failure of the bonding portion of the setting cement. As you know, once any of that debris moves, you cannot reset the stone. And, cleaning the debris creates very small irregularites compounding the problem. (Note that the basic impression of the setting layer is intact -- this is small amount of loose debris).I hope this additional detail helps. In a nutshell, the question is whether I can simply regrout all the joints (after cleaning, etc), not disturb the set but unbonded stones, and hope that a good grouting job holds everything in placeThanks again for you expertise and time.Ken
Yes, you probably can. But you'll have to do it right. Here's a link:
http://www.thisoldhouse.com/toh/print/0,17071,637230,00.html
Edited 11/10/2005 3:21 pm ET by JourneymanCarpenterT
Edited 11/18/2005 6:39 pm ET by JourneymanCarpenterT
Thanks again for the response. Instructions from both web sites are clear and manageable.Only difference: TOH calls for 3 sand/1 cement mix vs. 1/1 mix on UK site. Any thoughts?Finally, per your post, I'll leave the unbonded stones undisturbed and simply regrout. Any technique on how to reset the very small number of stones that have become slightly wobbly? Is there a shortcut to avoid chiseling out and replacing the setting bed>THanks again for the help and your patience.Ken.
I didn't post the site for the UK site. That was posted by storme, but I'm glad that you found it helpful. I would go with the 3:1 ratio. It's the same one I used in my original post.
Finally, regarding the slightly wobbly stones. Flagstone really isn't my specialty, and unfortunately I don't have any shortcuts for you. I'd just be careful not to damage the bed under the surrounding stones.
There's not much more I can tell you. You might be able to find more information at Over the Fence. You'll see a link at the top of the screen.
Best wishes.
Edited 11/18/2005 6:39 pm ET by JourneymanCarpenterT
site with good info:
http://www.pavingexpert.com/crazypav.htm
at the bottom of this page are links to jointing and pointing as well