Arched Fireplace Insert: Complete Guide for Homeowners

A curved brick or stone opening is one of the most charming features an older home can have, and also one of the trickiest to upgrade. Most fireplace inserts are rectangular boxes, so homeowners with arched openings often assume they are stuck choosing between a drafty open hearth and tearing out the masonry. They are not. An arched fireplace insert, or a standard insert paired with an arched surround panel, lets you keep the curved look while getting dramatically more heat and less draft. The key is measuring carefully and understanding how the insert and faceplate work together.

This guide explains how inserts fit arched openings, how to measure, which fuel types work, what the chimney liner requirement means, and what the project costs.

What an Arched Fireplace Insert Actually Is

A fireplace insert is a closed-combustion firebox that slides into an existing masonry or, in some cases, factory-built fireplace. It seals the opening with glass doors, draws combustion air in a controlled way, and pushes heat into the room instead of losing most of it up the chimney. Traditional open masonry fireplaces are notoriously inefficient; much of the heated room air gets pulled up the flue along with the smoke.

With an arched opening, the insert box itself is almost always rectangular. What makes it an arched fireplace insert is the surround, the metal faceplate that covers the gap between the insert and the masonry. Manufacturers offer arched surrounds shaped to follow the curve of the opening, and some offer arched door fronts or arch-top trim kits for specific models. Custom fabricators can also cut surrounds to match an unusual curve.

There are three common arch profiles you will see:

• Full round (semicircle): the top of the opening is a half circle, common in European-style and Mediterranean homes.
• Segmental or eyebrow arch: a shallow curve across the top, found in many mid-century and Craftsman brick fireplaces.
• Tudor or pointed arch: a curve that rises to a slight point, typical of Tudor Revival and Gothic-influenced houses.

How to Measure an Arched Fireplace Opening

Measuring is the step that determines whether your arched fireplace insert fits cleanly or leaves visible gaps. Take these measurements with a steel tape and record them in inches:

1. Front width at the bottom of the opening, where the hearth meets the side walls.
2. Front height at the sides, from the hearth floor to where the curve begins (the “springline”).
3. Peak height, from the hearth floor to the highest point of the arch.
4. Rear width at the back wall of the firebox.
5. Depth, from the front face to the back wall, measured at both the bottom and near the top, since many fireboxes slope forward.
6. Rear height at the back wall.
7. Damper and smoke shelf location, since the liner must pass through this area.

To capture the curve itself, tape a large sheet of kraft paper or cardboard over the opening and trace the arch with a pencil. Cut the template out and check it against the opening. Surround fabricators and dealers often ask for this template, or for photos with a tape measure visible, to confirm the curve.

The critical dimension for fit is usually the height at the sides, below the springline. The rectangular insert body must slide in under the lowest point of the curve, and the arched surround then covers the space above it.

Choosing a Fuel Type

Arched surrounds are available for gas, wood, pellet, and electric inserts, though selection varies by manufacturer. Each fuel has distinct pros and cons.

Gas inserts

Gas inserts are the most popular choice for arched fireplaces in homes where ambiance and convenience matter most. Most modern models are direct-vent, pulling combustion air from outside and exhausting through a pair of flexible liners (or a coaxial liner) run up the existing chimney. Many offer arched front options because traditional-style homes are a big part of their market.

Wood inserts

Wood inserts suit homeowners who want serious heat and have access to firewood. Look for current EPA certification, which means cleaner burning and less creosote. A wood insert generally has a larger, heavier body than a gas unit, so the height under the springline becomes even more important.

Electric inserts

Electric inserts slide in and plug into a nearby outlet or a dedicated circuit. They typically produce about 5,000 BTU of supplemental heat on a standard 120-volt circuit. For a purely decorative upgrade in a fireplace you no longer want to burn in, an electric unit with an arched trim can be the simplest option.

The Chimney Liner Requirement

An insert does not simply vent into the old masonry flue. Gas and wood inserts need a properly sized liner running from the insert’s flue collar to the top of the chimney. NFPA 211 and most manufacturers require a full-length liner for wood inserts, and direct-vent gas inserts require their own listed vent system.

• Why it matters: An old flue sized for an open fireplace is too large for an insert. The smaller exhaust stream cools as it rises through the oversized flue, drafts poorly, and deposits creosote or condensation.
• Typical materials: stainless steel flexible or rigid liners, sized to the insert’s outlet, often 6 inches for many wood inserts.
• Insulation: insulated liner wraps or poured insulation may be required, depending on the chimney’s condition and the liner listing.
• Termination: a top plate and rain cap seal the chimney top. The chimney itself should meet height requirements such as the 3-2-10 rule.

Arched openings add a challenge: the curved masonry and damper area can be tight. Installers sometimes need to remove the old damper plate or modify the smoke shelf to fit the liner through, which is a job for a qualified technician.

Installation and Safety

An arched fireplace insert installation generally follows these steps:

1. Chimney inspection: a Level 2 inspection, often including a camera scan, is commonly recommended whenever you change the appliance connected to a chimney.
2. Cleaning and repairs: sweeping the flue, repairing cracked mortar, and addressing any crown or flashing issues.
3. Liner installation: running the liner, attaching it to the insert, and sealing the top.
4. Gas or electrical connection: for gas units, a gas line and shutoff valve; for some units, an outlet for the blower.
5. Setting the insert and leveling it on the hearth.
6. Attaching the arched surround and checking that it seals against the masonry.
7. Testing draft, ignition, and carbon monoxide levels.

When to call a licensed professional: Gas line work, venting, and chimney liner installation should be handled by licensed and certified professionals, such as an NFI-certified hearth technician and a CSIA-certified chimney sweep. Permits are typically required. If your fireplace is in a pre-1978 home and you plan to scrape or sand painted brick or trim around the arch, assume lead paint may be present and use lead-safe work practices. Cutting or grinding brick and mortar releases crystalline silica dust, so masonry modifications should be done by pros with proper dust control. Install carbon monoxide alarms on every level of the home.

What an Arched Fireplace Insert Costs

Prices vary with fuel type, brand, and how much work the chimney needs.

• Electric insert with arched trim: about $400 to $2,000.
• Gas insert: about $2,500 to $5,500 for the unit, with total installed costs often $4,000 to $8,000.
• Wood insert: about $2,000 to $5,000 for the unit, with installed costs commonly $3,500 to $7,500.
• Arched surround: $200 to $900 for a manufacturer’s surround, more for custom fabrication.
• Stainless liner: roughly $1,000 to $3,000 installed, depending on chimney height and whether insulation is needed.
• Chimney repairs: highly variable, from a few hundred dollars for tuckpointing to several thousand for a crown rebuild.

Federal tax credits have at times applied to qualifying high-efficiency biomass (wood or pellet) appliances. Rules and amounts change, so confirm current eligibility with a tax professional before counting on a credit.

Styling the Arched Opening

The surround is the most visible part of the project, so choose a finish that fits the room. Matte black is the most common and pairs well with painted or natural brick. Brushed nickel, bronze, and pewter finishes suit traditional and transitional rooms. For Tudor or Spanish-style homes, a hammered or aged-iron finish can complement the architecture.

Think about the hearth and surrounding floor as well. A tile or stone hearth extension in front of the insert looks neat and protects nearby flooring from embers on wood-burning models. Where hardwood or LVP meets the hearth, a clean transition piece keeps the arch as the focal point. If the brick is dated, a limewash or mortar wash can refresh it without covering the arch’s character.

Frequently Asked Questions