QUESTIONGrout for Flagstone - What type of grout should I use for the flagstone on my driveway?
ANSWERANSWER - For grout in flagstone with varying thick and width joints you need to have a grout with a greater ratio of sand to cement. If you want a specific color and more consistency there are grout manufacturers who make a Saltillo type grout for wide joints over ½” wide.
If you make your own grout then use a 1:3 mix that is one part portland cement to 3 parts fine-graded sand (ASTM C144-02) and then damp cure. You can also find this pre-blended mix at building material suppliers.