The Brew Cabin

Hi. I hope you can help...your website is the best resource I have found regarding flagstone. I have a contractor scheduled to do landscaping, including creating a patio from Tennessee Blue flagstone. This flagstone is about one inch thick ( ) and cut in a random pattern. It will be laid over a combination of an existing cracked cement patio. bare ground where prior flagstone was removed and a concrete sidewalk. The original bid included a concrete base for the flagstone because we asked for concrete...my husband heard that it was the most durable base. However, on the eve of laying the stone, the contractor said that we should use a "crusher run" stone as a base with a mortar top layer instead of concrete. I am suspicious that this change in plan is due to his financial difficulty (we gave him the agreed-upon sum for supplies and he asked for another substantial sum because he spent the supply money on warehouse rent). My husband and I spoke with several other contractors, and the consensus is that the two bases are basically equivalent, although a few prefer concrete, believing it to be more durable. Money is not an object, as the original quote was for concrete, and level of difficult won't be a factor because the experienced contractor will be doing the work. Another factor is that our house is situated on the side of a small mountain and have significant drainage problems. Should we go with the concrete or the crushed stone/mortar as a base for flagstone? Thank you for your help.

Hi,

I'm not familiar with this Tennessee Blue flagstone stuff, but I assume it's pretty similar to our Yorkstone riven paving.

At only an inch thick (25mm), it really does need to be laid on a cement bound bedding, and if concrete is what is normally specified in your area, and concrete is what you agreed, then concrete is what you should get.

Laying on a mortar bed, on top of a crushed stone sub-base is fine as long as the ground beneath (the sub-grade) is suitable, but that's for UK conditions. I believe frost heave is a significant risk in some parts of the USA and therefore I'd be a little more cautious about it's use under those conditions.

If, as you hint, there are significant drainage problems with the sub-grade, then concrete is the safest option to follow. All-in-all, you should get what was oroiginally agreed, and I just hope you have all this in writing!

PS - I know this may sound daft to you, but is this Tennessee Blue Flagstone really blue in colour? Do you have any pictures?