Fireplaces
Stone fireplace surrounds: which stones take the heat.
A fireplace surround is the stone that frames the opening. The hearth is the stone on the floor in front of it. The mantel is the shelf above. We cut all three in our Hartford shop, from honed modern panels around a linear gas unit to carved marble around an old wood-burning firebox. You can see them in our fireplace gallery.
The question we hear first is whether a given stone can stand the heat. For most natural stone the answer is yes. The rules that actually shape the job are about the hearth and the mantel, and they come from the building code and from your fireplace's manual. This piece covers both, stone by stone, and then how a surround gets measured.
Which stones take the heat?
- Granite. Granite is highly resistant to heat and hard to wear down, which makes it a natural hearth stone where logs and tools get set down. Our granite page shows a granite surround and hearth set by our crew.
- Marble. Marble is the classic surround stone, and it is where marble is easiest to live with. A kitchen counter meets lemon juice and wine. A surround mostly meets heat and a duster. Carrara, Calacatta and darker stones like Nero Portoro all work. The marble page lists what is in the racks. If you are weighing marble for the kitchen too, read marble in a working kitchen first.
- Quartzite. Naturally heat tolerant and harder than granite, with veining that reads like marble. It suits a surround that has to match a quartzite kitchen in an open plan.
- Soapstone. The stone most at home next to a fire. Polycor, a North American quarrier, describes soapstone as a stone that conducts and retains heat, and shows a project where it lines the firebox itself in place of firebrick. It is softer than granite, so a dropped log can mark it. Small scratches sand or oil away, as our soapstone page explains.
- Quartz. Engineered quartz is crushed stone bound with resin. Our quartz page already says it does not love direct high heat. Cambria says quartz can be used for a surround, but tells you to check the fireplace manual and your fabricator first, because each fireplace is different. Quartz is a fine choice for the face of many gas units. It is the stone we look at hardest before cutting.
- Porcelain. Large-format porcelain and sintered slabs like Neolith and Dekton are heat resistant, and big thin panels can cover a whole wall around a linear gas fireplace with very few seams. In 2025 New York City's Office of Technical Certification and Research accepted Neolith as a non-combustible surface for exterior wall cladding. Our porcelain page explains why porcelain needs a shop that knows how to cut it.
Heat is rarely what rules a stone out. Weight, finish and what the fireplace maker allows usually decide it.
Which rules apply in Connecticut?
Connecticut builds to the 2022 State Building Code, which adopts the 2021 International Residential Code with state amendments. A 2026 code based on the 2024 edition was due on July 1, 2026. The state has delayed it while the Legislative Regulation Review Committee reviews it. Until it takes effect, the 2022 code governs, and your town's building official has the final word.
The code treats two kinds of fireplace differently.
- A masonry fireplace is built in place of brick or block, usually with a chimney. Section R1001 of the code sets the hearth size and the mantel clearance below.
- A factory-built fireplace or insert, which includes nearly every gas fireplace, must be installed according to its listing (section R1004). In practice that means the manual decides the hearth, the mantel height and what may touch the unit. The hearth must also be easy to tell apart from the floor around it.
How big does the hearth have to be?
For a masonry fireplace, the hearth extension in front of the opening has to reach at least 16 inches out and 8 inches past each side. If the opening is 6 square feet or larger, that grows to 20 inches out and 12 inches past each side.
Here is how that plays out. An opening 36 inches wide and 30 inches tall is 7.5 square feet. That puts it in the larger group. The hearth has to be at least 60 inches wide (36 plus 12 on each side) and 20 inches deep. Many older Connecticut fireplaces have openings that size, so measure before you fall for a slab that is too narrow.
Thickness matters too. A masonry hearth extension has to be at least 2 inches thick. The exception is a firebox raised 8 inches or more above the hearth extension, where 3/8 inch of stone, tile or other approved noncombustible material is allowed. That exception is why a thin stone hearth works in front of a raised firebox and not in front of one at floor level.
How close can a wood mantel sit?
For a masonry fireplace, the code keeps combustible trim and mantels at least 6 inches from the opening. Within 12 inches, anything combustible may stick out no more than 1/8 inch for every inch of distance from the opening.
- At 6 inches from the opening, wood trim can project 3/4 inch.
- At 10 inches, it can project 1 1/4 inches.
- Past 12 inches, this rule no longer limits it.
So a wood mantel shelf that sticks out several inches has to sit more than 12 inches above the opening. Stone does not have this limit, because it is not combustible. That is one reason people pick a full stone mantel when the room has a low ceiling. For a gas fireplace, ignore these numbers and read the manual. Many gas units call for more room above the opening than the masonry rule does.
How is a stone surround measured?
The stone is cut to the finished opening, so templating happens once the fireplace or insert is in place and its trim is known. These are the dimensions that decide the cut:
- The opening. Width and height, measured to the firebox or the unit's trim.
- The legs and the header. The pieces down each side and across the top. A classic surround is three or four pieces. A full wall is cut from as few slabs as the size allows.
- The hearth. Width and depth from the rules above, and whether it is flush with the floor or raised.
- Thickness. Stone comes in 2cm and 3cm. Thicker stone closes the opening down a little and changes how the trim kit on a gas insert meets the face. The Calacatta Viola in our gallery is 2cm, polished and mitered at the corner so the veining turns instead of stopping at a seam.
- The wall and floor behind it. A full-height slab is heavy. Use Natural Stone notes that the floor has to be rated for the stone you choose, which matters more on a second floor or over a basement than on a slab.
Bring the fireplace manual, or the model number, when you come to the yard. It answers half the questions above before anyone measures.
Should you match the kitchen?
In an open plan, a surround cut from the same stone as the island ties the rooms together. A three-piece surround takes far less stone than a kitchen, so ask whether your kitchen slabs leave enough when you tag your kitchen slab. In a separate living room, the fireplace is the one place a bold stone like Nero Portoro or a deep green marble can carry a whole wall.
Our slabs stand outside at 97 Airport Road in Hartford, weekdays 8:30 to 4:30 and Saturday 9 to 1. Come see the stone in daylight, or tell us about the fireplace and we will get back to you within one business day.