Question
I am in the midst of a homebuilding project and while my plans did not specify that the front and side entry porches should have bluestone field, that is what I plan on doing.  The question is:  My GC is responsible for laying the concrete field in those areas, how much room should I leave for the future install of the bluestone by my landscaper?

Answer
Tali"
Bluestone is a common name used to describe a stone type available from a number of sources. It is generally a dense slate type stone with a consistent grayish to gray blue or gray green tone. The term Bluestone does not dictate any one size or thickness. Often, it is referred to as "Pennsylvania Bluestone". It only dictates the type and color of the stone.

You will need to source your stone and then determine what thickness you desire based on your budget and the various types and sizes that are readily available in your area. I personally would not use anything thinner than 3/4" for exterior application on a slab. At a bare minimum you need about 3/4" for stone thickness, plus 1/4 for variations in pieces, and a 1/2 mortar bed. So you need 1.5" minimum. If you plan to use large flag stones say 2 to 3 feet wide and long then the thickness needs to be more like 1 to 1.5" Smaller pieces can be thinner. If you go down to pieces less than 12" in any dimension you could go to 1/2 thick (like times). Don't forget to account for any needed slopes or gradients to drain water off these surfaces. Between 1/8 and 1/4" fall per foot is best for small pedestrian stoops and porches.

Best of Luck,

Sean J Murphy

www.amenityarchitects.com
www.seengineering.com