Tukwila, WA — King County
Gas Fireplace Insert Installation
Your old wood-burning fireplace can become a clean, efficient gas fireplace without touching your surround or mantle. We install gas fireplace inserts the right way — properly lined, code-compliant, and built to last.
What Is a Gas Fireplace Insert?
A gas fireplace insert is a sealed gas appliance that slides directly into your existing masonry or prefab firebox. Think of it as dropping a high-efficiency gas unit into the shell of your old fireplace — you keep your surround and mantle exactly as they are, but you get all the convenience and warmth of modern gas.
- ✓ Fits your existing firebox — the insert slides into the opening you already have, no major construction required
- ✓ Sealed combustion unit — unlike an open hearth, a gas insert contains combustion gases and pushes warm air efficiently into the room
- ✓ Uses your existing chimney flue with a liner — a flexible stainless steel liner runs up through your existing flue, so your chimney still does its job safely
- ✓ Far more efficient than an open hearth — open wood fireplaces lose most of their heat up the chimney; a gas insert delivers that heat into your living space
Gas Insert vs. Gas Logs — Which Is Right?
Both options convert your wood-burning fireplace to gas, but they work very differently — and the right pick depends on what you're after. Here's the honest comparison.
Gas Insert
- ✓ Sealed unit — combustion is isolated from your living space
- ✓ High efficiency — most heat stays in the room, not the flue
- ✓ Looks like a built-in fireplace with a finished surround trim
- ✓ Requires chimney liner installation
- ✓ The right choice if actual heating output matters
Gas Logs
- ✓ Open hearth — uses your existing damper and flue as-is
- ✓ Lower installation cost and simpler setup
- ✓ Ambiance-focused — realistic flame, classic fireplace look
- ✓ No liner required in most cases
- ✓ Less efficient — more heat escapes through the open flue
We'll tell you honestly which makes more sense for your situation — budget, firebox condition, and how you plan to use the fireplace all factor in.
Is a Gas Insert Right for You?
A gas insert is one of the most practical fireplace upgrades we install. Here are six situations where it's usually the right call:
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You have an old wood-burning fireplace you rarely use — because it's too much work to maintain, and a push-button gas fire is what you actually want.
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You want gas convenience without a remodel — a gas insert fits your existing opening, so you keep your surround, mantle, and hearth exactly as they are.
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You want to keep your existing fireplace surround — the insert trim panel fits flush against your current facing, so the finished look is clean and intentional.
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You're done hauling wood and cleaning ash — gas inserts eliminate creosote buildup, ash cleanup, and the hassle of keeping a wood supply stocked and dry.
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You want real heat output, not just ambiance — inserts are rated for efficient room heating and can meaningfully reduce how hard your HVAC works in the space where the fireplace lives.
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Your old masonry fireplace is drafty — the sealed combustion chamber in a gas insert eliminates the cold air infiltration that open-hearth fireplaces are notorious for when not in use.
Our Gas Insert Installation Process
Every gas insert installation we do follows the same four steps — no shortcuts, no guesswork.
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1
Firebox Assessment
We check your firebox dimensions, masonry condition, and flue to nail down the right insert size and venting approach. Fit matters here — a properly sized insert performs better and looks intentional, not crammed in. If there's anything going on with the masonry or flue that needs attention first, we'll tell you before we recommend anything.
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2
Liner & Prep Work
We run a flexible stainless steel liner down through your existing chimney flue — this is standard on every gas insert install, not an upgrade. We also prep the gas connection and confirm your existing line has enough capacity. If a new line or capacity upgrade is needed, we coordinate that before installation day. No surprises when we show up.
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3
Insert Installation
We set the insert into the firebox opening, connect it to the liner and gas supply, and fit the surround trim flush against your existing facing. We protect your hearth and mantle throughout, and we don't call it done until the trim is seated properly and the unit sits right in the opening — not just close enough.
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4
Testing & Commissioning
We run the insert through a full test — ignition, flame adjustment, blower, controls — and confirm there are no leaks and that the venting is drawing the way it should. Before we leave, we walk you through how everything works: the remote or wall switch, flame height, thermostat features, whatever your model has. You shouldn't need to figure anything out on your own.
Service Area
We install gas fireplace inserts throughout King County, Pierce County, and Snohomish County — including Tukwila, Seattle, Bellevue, Renton, Kent, Federal Way, Auburn, Kirkland, Tacoma, Everett, and the surrounding communities.
Frequently Asked Questions
What is a gas fireplace insert?
It's a sealed gas appliance that fits directly into your existing masonry or prefab fireplace opening. It takes the place of your open hearth with an enclosed, efficient gas unit — real flames, reliable heat, push-button convenience — without touching your surround or mantle. The insert connects to a flexible stainless steel liner that runs up through your existing chimney flue, so the structure stays put and the installation is far less disruptive than building from scratch. Most homeowners are genuinely surprised how clean the job is.
Will a gas insert fit in my existing fireplace?
In most cases, yes. We measure your firebox carefully during the initial assessment and match it to an insert that fits the way it's supposed to. Inserts come in a wide range of sizes — compact prefab openings to big masonry hearths — so there's usually something that works. Every now and then a firebox has unusual dimensions or a structural problem that limits the options, and we'll tell you that plainly before anything is ordered or scheduled.
Do I need to keep my chimney for a gas insert?
Yes — your chimney stays put. A gas insert uses a flexible stainless steel liner run inside your existing flue to carry combustion gases safely to the outside. The liner goes through the chimney, not around it, so your footprint doesn't change and the installation is far less invasive than starting fresh. The liner is sized specifically for gas appliances, so it vents correctly even if your original flue was built for a wood-burning fireplace.
How much does a gas insert installation cost?
It depends on your firebox size, the insert model, liner length, and whether any gas line work is needed. We give you a detailed, upfront estimate before anything starts — you know exactly what you're looking at before we order a thing. Reach out and we'll put together a quote specific to your home.
Is a gas insert more efficient than a regular gas fireplace?
Yes, significantly. Gas inserts are sealed units with high efficiency ratings — many are 70–80% or better, which means most of the heat they produce actually stays in your room. An open-hearth wood fireplace loses well over half its heat straight up the chimney. If you want to actually warm a room instead of just watching a fire, an insert is one of the most efficient ways to do it. And compared to a natural-vent gas fireplace — which exhausts through an open flue — the insert's efficiency advantage is real if heating output matters to you.
How long does a gas insert last?
With proper maintenance, 15–25 years is a realistic lifespan. The parts that wear — thermocouple, igniter, gas valve — are all serviceable components. They get replaced as needed, not the whole unit. The biggest thing that affects how long an insert lasts is whether it gets serviced regularly. Annual tune-ups catch small problems before they turn expensive and keep the unit running efficiently. Most of the inserts we service are in great shape well into their second decade.
Ready to Convert Your Fireplace?
Call or text to schedule a free assessment. We'll come out, measure your firebox, walk you through what fits, and give you a straight upfront estimate.