Last Updated on October 20, 2026 by Umar Farooq
Pennsylvania flagstone is a trade name, not a rock type. It usually means sandstone quarried in Pennsylvania and sold as bluestone in blue, "full color" or lilac, in irregular or pattern-cut slabs about 1 to 1 1/2 inches thick. The word tells you roughly where it came from, not how dense it is or how well it will wear. Stone Center prices bluestone at $25 to $35 per square foot and ordinary flagstone at $15 to $25.
I tried to find a standard that defines the term and did not find one. The search results are stone yards and local installers, which is useful for specs and prices. Our bluestone pavers guide covers the rock itself; this page is about ordering it.
What the name actually covers
Look closely at the Stone Center flagstone-vs-bluestone article and you find the answer in a product link rather than the text: the listing for "Full Color Bluestone Irregular" carries the web address slug "PennsylvaniaFCIrregular." So "Pennsylvania flagstone" in a catalog often means Pennsylvania full-color bluestone, laid as irregular flagstone. The article itself never defines Pennsylvania flagstone as a category.
Unilock, a paver manufacturer, says bluestone is quarried in the northeastern US and Canada, mainly Pennsylvania and New York State. One stone yard in New Jersey sells bluestone irregular flagstone in blue, full color and lilac. A Pennsylvania installer describes its stone as grays with tints of blue, green, tan, brown, rust and plum, selected stone by stone.
Treat the color names as sales grades, not geology, and ask to see a pallet, not a photo.
Thickness: 1 inch, 1 1/2 inches or a 6 inch tread
The stone yard I read offers its Pennsylvania bluestone irregular flagstone in 1 inch or 1 1/2 inch thicknesses. The installer I read, Kleinberg near Philadelphia, sets 1 1/2 inch stone for patios on a compacted base and uses 6 inch thick flagstone for step treads.
Our flagstones guide gives the rule of thumb: stone thinner than about 1 1/2 inches belongs on a concrete slab, and thicker stone can go dry on a compacted base. So the 1 inch option is a mortar-set choice, and the 1 1/2 inch is the one for a dry-laid base. Pay attention to this on the order sheet, because it decides your whole construction method.
Irregular or pattern-cut: say which on the order
Irregular flagstone keeps its natural edges and is fitted like a jigsaw. Pattern-cut is sawn into squares and rectangles, which lays faster and gives tighter joints. Stone Center sells both; the installer I read sets each stone individually at grade, which is the slower way.
When you order, write down:
- Stone name and color (blue, full color or lilac)
- Thickness (1 or 1 1/2 inches)
- Irregular or pattern-cut
- Square feet, plus extra for cuts and rejects
- A request to see the pallet before delivery
How local installers actually lay it
Kleinberg's page describes a compacted base of modified and screened stone. (The page has a typo here, so this is my reading.) It also describes a pitch of about 1.5 to 2 percent so the patio looks level but sheds water away from the house.
That lines up with the figures this site uses. ICPI Tech Spec 2 gives a minimum surface slope of 1.5 percent, and the IRC (R401.3) asks for at least 2 percent on hard surfaces within 10 feet of a foundation. Two percent is about 1/4 inch per foot. Check your local code. Our cost of flagstone pavers guide covers what the labor adds.
What it costs next to ordinary flagstone
Stone Center lists flagstone at $15 to $25 per square foot, or about $300 to over $500 per ton, and bluestone at $25 to $35 per square foot, or $450 to $700 per ton. Those are supplier figures from a 2025 article. Pennsylvania flagstone in the full-color range sits on the bluestone side of that line, going by the product listing. Delivery, base stone and labor are extra.
My one strong opinion: do not pay extra for the name. Pay for thickness and a sample. A thin, soft Pennsylvania stone on a thin base is a very expensive way to own a wobble. The pavers, or here the stone, are the finish. The base is the patio.
If you want the look without the price, an irregular concrete paver is the cheaper option. See our irregular pavers guide. For how the stone itself compares with granite, slate and travertine, see natural stone pavers.
Buy the spec, not the state
The word Pennsylvania tells you the stone's origin. The thickness, the water absorption and how it was split tell you whether it will last. Get a sample, ask for the absorption figure, and match thickness to your base before you place the order.
When the pallet arrives and half the stones look nothing like the sample, you have learned why "full color" is a range and not a promise.
FAQ
Is Pennsylvania flagstone the same as bluestone?
Usually, in catalogs. One supplier's "Pennsylvania FC irregular" listing is Full Color Bluestone Irregular. The term is a trade name, not a defined rock type.
How thick should Pennsylvania flagstone be for a patio?
Yards sell it in 1 inch and 1 1/2 inch. One Pennsylvania installer uses 1 1/2 inch for patios on a compacted base and 6 inch treads for steps. Thinner stone is better on a concrete slab.
What colors does Pennsylvania flagstone come in?
One stone yard lists blue, full color and lilac. An installer describes grays with tints of blue, green, tan, brown, rust and plum.
How much does Pennsylvania flagstone cost?
Stone Center's figures are $25 to $35 per square foot for bluestone and $15 to $25 for flagstone, before delivery, base and labor. Ask for local quotes.
Is Pennsylvania flagstone slippery?
Unilock says bluestone can be very slippery when wet, a concern around pools and hot tubs. Our bluestone guide notes both finishes give grip, so test a sample wet before using it near water.
