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What should I use to fill these flagstones joints? Joint size is between 1-4". Is mortar my best option? Will polymeric sand work with these huge gaps?

  • 2
    Possible duplicate of What mortar should be used for flagstone?
    – Kris
    Jun 2 '19 at 18:09
  • Hello, and welcome to Home Improvement. Those gaps are indeed huge. What's the traffic on this going to be like? What's underneath the flagstones? Jun 2 '19 at 19:45
  • Hi Daniel. Lots of traffic. Its ground underneath.
    – Margol
    Jun 2 '19 at 19:57
  • 1
    Is it flagstone or a concrete poured walkway molding? Mortar will crack and break in gaps that large. The best option may be to use a sand filler. Wet it down, sand fill and sweep, wet that down. Repeat until it is the desired height. You could even add a little Portland cement to the sand, just to help keep it together. Paver sand is what I would use, not play sand.
    – Jeff Cates
    Jun 2 '19 at 22:50
  • Not sure i think its flagstone because the are all diff size
    – Margol
    Jun 3 '19 at 0:46

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