[precision1]

Please let me start out by saying I have been reading this forum ever since I found it 8 months ago. I am very impressed with the collection of proffesional knowledge found here!!! Hardscaping is kind of a hobby of mine so reading this forum is something I look forward too. I have much experience with concrete, and have completed one fair size brick paver job. My questions are regarding a sidewalk/patio that is in progress at my home.

I am installing flagstone over a poured concrete base. The pour is 4-5" thick
4'000 PSI concrete with a grid of 1/2" rebar 16" OC. It is poured over 4-5" of 3/4" stone with fabric under the stone. I am located in southeastern Pa. Our winters see plenty of freezing, but not the super frigid cold of alot of the northern states experience.

My first question is will sandstone flags hold up in our climate? I have spoke with a local supplier and they tell me they no longer sell them as they do not hold up well. I do not know if this is true or if they were just feeding me a line. My other option is to use Pa. flagstone, but I really like the color of sandstone. I will be setting these in mortar.

My other question is regarding the joints. I am planning on doing alot of cutting as I want to keep the joint width to a minimum. I like the look of the "broken ice" pattern that I found here on this forum. This leads me to my next question. Since I am setting these flags in mortar, do I have to grout the joints with mortar or can I just sweep in Polymeric sand? Does the grout/mortar joint seal this application better than the Polymeric? I would prefer to use the sand as I really do not want the joints to stand out. Thanks in advance for all your help!