Bluestone treads appear on exterior stairs in New England almost as commonly as granite. They are lighter, easier to handle, and produce a slightly warmer surface than granite. The specification for a stair tread is different from a patio slab or a pool coping — the thickness, the nosing, and the finish are all determined by the specific demands of a surface that is stepped on thousands of times a year at the most vulnerable point of each stone.
Bluestone treads in natural cleft have the slight texture and color variation that read correctly on exterior stairs at traditional New England properties. Thermal finish is an alternative with better slip resistance in wet conditions. The color is the same blue-grey to warm grey as all Pennsylvania bluestone, and it reads as stone in a way that concrete or brick treads do not.
Bluestone stair treads are Pennsylvania or New York bluestone cut to tread dimensions: minimum 1.5 inches thick for exterior use, 2 inches preferred for treads over 4 feet wide. Standard tread depth is 12 to 14 inches. Nosing is eased — a slight rounding at the leading edge — not sharp. The underside is sawn flat for a stable bearing on the riser below.
Bluestone treads are durable in New England conditions but vulnerable at the nosing — the leading edge of the tread that receives the most impact. A sharp arris at the nosing chips. An eased nosing does not. The tread must be fully supported across its width; unsupported spans over 6 inches at the back edge will eventually crack under load.
Bluestone treads are correct on exterior stairs at traditional New England residential properties where the stair connects grade to grade — terrace to garden, upper lawn to lower — and where granite would feel too heavy or too formal. For entry stairs at the front door, granite is the correct specification. Bluestone is the correct material for secondary exterior stairs.
From stone yards. Specify Pennsylvania bluestone, natural cleft face, sawn bottom, 1.5 to 2 inch thickness, eased nosing, to the tread dimensions required. Provide exact width — bluestone treads are cut to order.
Pennsylvania or New York bluestone, natural cleft face, sawn bottom, 1.5-inch minimum thickness (2-inch for widths over 4 feet), eased nosing, for exterior stair treads at traditional New England residential properties. Full bearing across tread width required. Thermal finish acceptable where slip resistance is the priority. Not appropriate for primary entry stairs — specify granite there.
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