Calculating Bluestone Thickness for Porch Installation

A homebuilder needs to know how much height to leave for bluestone installation over concrete porch slabs. Bluestone varies in thickness; term refers to color/type (typically Pennsylvania bluestone), not dimensions.

Minimum Height Allowance

• Stone thickness: 3/4" minimum for exterior slabs
• Thickness variation: +1/4" for uneven pieces
• Mortar bed: 1/2" minimum
• Total: 1.5" absolute minimum

Adjustments for Stone Size

• Large flagstones (2-3 ft): 1-1.5" thick → allow 2-2.25" total
• Small pieces (<12"): 1/2" thick → allow 1.25" total

Critical Details

• Slope: 1/8" to 1/4" per foot for drainage
• Sand base: 6" concrete sand (not masonry sand)
• Back-butter uneven pieces to achieve level surface
• Source stone first to confirm actual thicknesses available locally

Communicate these requirements to the general contractor before concrete pours.