Chimney Liner Alloy: 316Ti vs 304 Stainless — Which You Need
Stainless chimney liners come in more than one grade. What separates 304 from 316Ti stainless is which fuels each can survive, and choosing the wrong alloy is a hidden failure that stays hidden until the liner corrodes. Matching the alloy to your fuel is the whole decision, and here is how to make it.
Reline a chimney and the decision that matters most disappears behind the finished work: which stainless alloy went up the flue. Quotes will show one of two numbers, 304 or 316Ti, and the two are not interchangeable; each survives different fuels and different exhaust chemistries, and putting the cheaper alloy where the harsher-duty one belongs is a failure that hides until the liner corrodes from the inside. Specifying the right alloy once carries a small premium against the cost of relining twice, which is exactly why it matters who specs the job.
01304 stainless — the wood-burning standard
Start with 304 stainless steel, a strong, corrosion-resistant alloy and the appropriate, code-recognized choice for many wood-burning appliances. Exhaust from a clean wood fire is comparatively benign, and a correctly sized, correctly installed 304 liner stands up to it across a long service life. On a straightforward wood-burning reline that will stay wood-burning, 304 is often precisely the right specification; charging you for a harsher-duty alloy you do not need is no more honest than under-speccing the one you do.
There is a limit, though. The resistance 304 offers runs out against the acidic, condensing exhaust of certain other fuels, so the alloy that is perfect in a wood flue can pit and fail in a high-efficiency gas or oil flue. The fuel, not the budget, has to drive the choice.
02316Ti — the all-fuel, harsher-duty alloy
316Ti is a titanium-stabilized 316 stainless, and the chemistry earns its keep. Molybdenum in 316 sharply improves resistance to the chloride and acid attack found in tougher exhaust streams, while the titanium stabilization protects the weld-affected zones from a specific corrosion failure under heat. What you get in practice is an alloy rated for all fuels, wood, gas, oil, and pellet, and the right call wherever the exhaust runs acidic or condensing, or wherever the fuel might change down the road.
Nothing makes the case for 316Ti like high-efficiency gas and oil appliances. They pull so much heat from the exhaust that the flue gases cool and condense inside the liner, and that condensate is acidic enough to attack a lesser alloy. Coastal and high-chloride environments point the same direction. When in doubt, or when a single liner must stay future-proof against a later fuel conversion, 316Ti is the alloy that never has to be revisited.
03Why the wrong alloy is a hidden, expensive mistake
Because a liner corrodes from the inside, where no one ever looks, an under-specced alloy gives no warning. It simply fails years ahead of schedule, surfacing as a breach at the next camera inspection or, worse, as a venting problem that puts combustion gases where they should never be. Once the symptom appears, the only remedy is relining all over again, and the bargain quote that shaved a few hundred dollars off the alloy quietly becomes the most expensive liner you will ever buy.
Budget relines tend to hide a second shortcut here: the so-called slammer, a non-connected liner dropped into an oversized flue where it vents into a void, condenses, and underperforms no matter what alloy it is made of. What a premium reline delivers is the full specification: a full-length liner of the correct alloy, sized correctly to the appliance, insulated where code and performance require it, carrying a continuous positive connection from the appliance collar to the cap, and documentation that proves every one of those points. Since the alloy disappears behind the masonry and cannot be inspected later, it is the detail you most need specified honestly before the work begins.
The fuel decides the metal. For many wood-burning systems, 304 stainless is the right, cost-appropriate liner; 316Ti is the all-fuel, harsher-duty alloy that stands up to the acidic, condensing exhaust of high-efficiency gas and oil, and the safe call whenever the fuel might change down the road. Because a wrong alloy stays invisible until it corrodes, ask for a quote that names the alloy, sizes the liner to the appliance, and documents the install. Specified honestly once, a stainless reline can serve the remaining life of the home.
Every recommendation in this guide starts from one place: a graded, photographed inspection. Book a chimney inspection and pair it with a chimney liner — one standard, one paper trail, every job.