Before you convert a wood fireplace to gas, get the chimney inspected. That is the one step homeowners skip most often and the one that matters most. A gas log set or gas insert is only as safe as the flue it vents through, and in the Seattle area that flue is usually a masonry chimney built decades before the appliance. NFPA 211 recommends a Level 2 inspection, which includes a camera scan of the full flue, any time a fireplace changes fuel type. Wood to gas is exactly that change.
The reason is simple. Gas exhaust is cooler and wetter than wood smoke. A flue that handled a wood fire for fifty years may have cracked tiles, washed-out mortar joints, a failed crown, or a damper that cannot be made to stay open, and none of that stops a wood fire from burning. It does matter for gas, where condensation, drafting, and an open vent path are the whole game. Here is what we look at on a chimney inspection before a conversion, and what the findings usually mean for the project.
First, which kind of conversion?
"Converting to gas" covers three different projects, and the chimney requirements differ.
Vented gas logs
A gas log set sits in the existing firebox and vents up the existing chimney with the damper fixed open. It looks the most like a wood fire and is the cheapest to install. It is also the option that leans hardest on the condition of the old flue, because it uses the full masonry chimney as its vent, and because the damper stays open year-round, the chimney is always open to rain and animals from above and always pulling warm house air out the top.
Direct-vent gas insert
A sealed insert slides into the firebox and vents through a flexible liner run up the old chimney, usually with a second pipe or coaxial liner bringing combustion air in. This is the most common conversion we see in Seattle homes. The old flue becomes a chase for the new liner rather than the vent itself, which is better for efficiency and for the masonry, but the liner still has to fit through the flue, which means the flue has to be clear, straight enough, and free of collapsed tile.
Vent-free gas logs
Some products are designed to burn without venting. Whether they are allowed, and whether you want one in a tightly built Puget Sound house, is a conversation to have with your installer and your local building department. We do not install gas appliances; our job is the chimney and firebox they sit in.
What we check before a conversion
The flue liner, top to bottom
A Level 2 inspection puts a camera down the entire flue. We are looking for cracked or shifted clay tiles, missing mortar between tiles, offsets, and any spot where the liner has collapsed or is missing altogether. Older Tacoma and Shoreline homes in particular, where the housing stock has a median build year of 1967 and 1969 respectively, often have unlined or partly lined chimneys. An unlined flue can still serve as a chase for an insert liner, but it is not a safe vent for open gas logs.
The smoke chamber and damper
The smoke chamber is the funnel above the firebox. Corbelled brick with open joints here is a common find. For a vented log set the damper must be permanently fixed open; a damper that is rusted, warped, or missing a plate may need repair or replacement before a conversion.
The firebox
Gas logs and inserts put heat into the same firebox the wood fire used. Cracked firebrick, crumbling refractory mortar, and gaps behind the back wall all need attention first. Our fireplace crack repair starts at $299, and fixing it before the insert goes in is far easier than pulling the insert later.
The top of the chimney
This is where Seattle weather does its damage. Sea-Tac averages 40.34 inches of rain a year, with about 73% of it falling from October through March, and winter lows hover just above freezing so wet masonry freezes and thaws repeatedly. We check the crown for cracks, the cap for rust or absence, and the top courses of brick for spalling. A conversion is the right time to fix a bad crown (crown rebuild starting at $299) and to fit a proper cap, because once a gas insert liner is in place, the cap is what keeps rain off the liner termination.
Flashing and the chase
If water is already getting in at the roofline, a new gas appliance will not fix it and may hide it. We check the step and counter flashing. On factory-built fireplaces in framed chases, which are the majority in post-1985 homes across Renton, Redmond, Bothell, and Gig Harbor, we check the chase cover for rust and the chase framing for rot. A rusted cover is a $299 starting-price chase cover replacement; a rotted chase is a bigger job.
Clearances and combustibles
In the attic and around the chimney we look for framing or insulation in contact with the flue, and for evidence of past heat damage. Gas inserts and their liners have clearance requirements of their own.
What the findings usually mean
- Clean flue, sound crown and cap: you are ready for either a log set or an insert. Keep the inspection report for your installer.
- Cracked or missing liner tiles: open gas logs are off the table until the flue is relined. A direct-vent insert with its own liner is often the practical path, provided the flue is clear enough to pull the liner through.
- Collapsed tile or heavy debris in the flue: the flue needs a chimney cleaning to clear it, and possibly repair, before any liner can be installed.
- Failed crown, cap, or cover: fix these first. They are inexpensive relative to the conversion and they protect the new equipment.
- Firebox damage: repair before the appliance goes in.
- Animal nest: remove it before anything else. Never light a fire to drive animals out, and be aware that chimney swifts are protected under the Migratory Bird Treaty Act.
A few Seattle-specific notes
The fireplace you are converting is probably older than you think. Seattle's median home was built in 1976 and about half of the city's homes date from before the late 1980s, so a large share of wood fireplaces here are in 1920s to 1960s masonry chimneys that have been through a lot of wet winters. In Seattle, Tacoma, Edmonds, Lakewood, and Shoreline, expect masonry; in the newer subdivisions of Auburn, Redmond, and Gig Harbor, expect a factory-built fireplace in a framed chase, which is a different conversion conversation because the existing unit is a listed appliance and the insert must be compatible with it.
Moss is also a factor. Western Washington moss spreads fastest from October through April on shaded, slow-drying surfaces, and it holds water against the brick. A chimney that has a green cap of moss on the crown is telling you the crown is staying wet.
What we do and do not do
We inspect and repair the chimney, flue, crown, cap, chase, flashing, and firebox, and we clear blockages and nests. We do not run gas lines, install gas appliances, or work on valves, pilots, or regulators. Your gas installer handles the appliance; we make sure the chimney it vents through is sound. If you ever smell gas, leave the house and call your gas utility or 911 from outside. Do not try to find or fix the source yourself.
What to do next
Book a Level 2 inspection before you sign with an installer, not after. You will get a camera view of the flue, a clear list of anything that needs repair, and a free quote for that work. If you already have a quote from another chimney company, we will give you a free second-opinion quote and match their price with a 10 to 25% discount. Same-day service is often available in King, Pierce, and Snohomish counties, and we reach Gig Harbor by the Tacoma Narrows Bridge. Call 206-453-2045. If you are not happy with the work, we are not done.
Questions homeowners ask
Do I need a chimney inspection before converting a wood fireplace to gas?
Yes. NFPA 211 recommends a Level 2 inspection, including a camera scan of the full flue, whenever a fireplace changes fuel type. It confirms the liner, smoke chamber, firebox, crown, and cap are sound before a gas appliance depends on them.
Can I put gas logs in an unlined chimney?
Open vented gas logs use the masonry flue as their vent, so an unlined or badly damaged flue is not a safe match. A direct-vent insert with its own liner run up the chimney is usually the practical option in that case, as long as the flue is clear enough to pull the liner through.
What is the difference between gas logs and a gas insert?
Vented gas logs sit in the open firebox and vent up the existing chimney with the damper fixed open. A direct-vent insert is a sealed unit with its own liner that uses the old chimney as a chase. Inserts are more efficient and easier on old masonry; logs look more like a wood fire.
Does Seattle Chimney Repair Services install gas fireplaces?
No. We inspect and repair the chimney, flue, firebox, crown, cap, chase, and flashing that the gas appliance depends on. A gas installer handles the appliance and gas line. We do not work on gas valves, pilots, or lines.
What repairs are common before a gas conversion in Seattle?
Crown rebuilds (starting at $299), cap or chase cover replacement (chase cover starting at $299), firebox crack repair (starting at $299), flue cleaning to clear debris, and removing animal nests. Fixing these first protects the new appliance.
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