Asked on Aug 24, 2014

Cement alternative for flagstone patio joints?

by Toshiba
We dry laid flagstone between our porch and patio. The flagstone was laid on sand and the joints are filled with sand. Looks great and the stone does not move or wobble, however, since the flagstone had to be laid on on a slight slope to the porch, when a heavy rain comes the joint sand washes out towards the patio. We also constantly get weeds in the joints and dont want to use weed killer because the the runoff goes into the yard onto the grass. Polymeric joint sand and gator sand will not because the joints are to big (up to 5in). Ground cover, pebbles, and mulch are not an option. Cement is a last resort. Any ideas are welcome.
Flagstone on slight a lope towards patio with sand joints.
  9 answers
  • Trina Heaster Grove Trina Heaster Grove on Aug 25, 2014
    Did you put land scale fabric under the sand? Did you use polymeric sand between the flagstones? If not, you can plant thyme between the gallstones to keep the weeds down. We put a Gladstone path in a few years ago and took it out because it had so many weeeds
    • Toshiba Toshiba on Aug 25, 2014
      No landscape fabric or polymeric sand used, the joints are too large for polymeric sand.
  • Dorothy Dorothy on Aug 25, 2014
    The only thing I can think of would be planting some kind of very low, very traffic tolerant ground cover or picking up the stones, raking or sweeping out the sand, laying a weed barrier, leveling the area without a slope, resetting the stones and replacing the sand with something (perhaps being level would allow for polymeric sand?) less likely to wash out (maybe small size gravel?). For plantings there are several that come to mind....creeping wooly thyme, a tiny mint (the name of which escapes me at the moment).
  • Darla Darla on Aug 25, 2014
    Crushed shale can pack down very hard. You might try that.
  • Toshiba Toshiba on Aug 25, 2014
    I might try the shale. We cant do any plants because of the heat here in SC, the stones get too hot, and the sprinklers do not cover the flagstone area.
  • Moxie Moxie on Aug 25, 2014
    They make a product called polymeric sand (brick and paver suppliers can usually get) that you use in lieu of regular sets harder after two water soaks.
  • Barb Burnham Barb Burnham on Feb 11, 2015
    Never heard joints too wide for polymeric sand. Verify the information. Howevrt, there is a spray on product you can use on fines (sand to decomposed granite size) that is a sealant adhesive. It forces the granules to stick together as a solid flexible surface. We are having our entire driveway graded, covered with decomposed granite then sprayed. They spray once, 2 was or so later then in one year -done for life. We will be able to drive over it daily (UPS/FEDEX trucks too) and it still look natural to our desert, prevent erosion and carefree. A sand/gravel store would know of it. They did not mention a weed block fiber down first, but I would still ask the question. If that isn't plausible for any number of reasons, I would go with a creeping Thyme that takes foot traffic. If it could take the Las Vegas heat, you are fine in S.C. Good luck
  • Valerie Valerie on Apr 10, 2016
    I know that you are not keen on cement, but I just thought I would mention that, when faced with a similar situation, I put dry cement in between pavers, and then added the water on to the dry cement. It was quick and easy, as I had been wary of trying to get cement into the narrow areas.
  • Ell107352835 Ell107352835 on May 26, 2024

    I just used polymeric sand - Gator Dust - on my patio. It looks very similar to your photo. The Gator Dist we used said it would work with joints up to 4-5” I think. There are different versions so look for the one that accomodates wider joints. Ours looks good now - hope it holds up!!

  • Hi Toshiba! You can check out this article all about flagstone. Hope this helps!