Guide · Flues
316 or 904 chimney liner: which grade do you actually need?
Choose 316 grade for a stove burning dry wood a few evenings a week; choose 904 grade if the stove runs daily, is your main heat source, or burns smokeless fuel regularly. The 904 costs more up front and lasts significantly longer in hard use, so the honest answer is how hard your stove will work.
Updated 11 July 2026
What the numbers mean
Both are grades of stainless steel used in flexible chimney liners. The difference is corrosion resistance: burning wood and especially smokeless fuels produces acidic condensates inside the flue, and 904 grade steel resists that attack far better than 316. Same job, different armour.
Neither is a budget trick; both are legitimate liners we fit routinely. The specification question is simply how much acid, heat and time your liner will face.
When 316 is the right call
For the classic Yorkshire pattern, a stove lit on winter evenings and weekends, burning properly dry wood, 316 is a sound choice that serves for many years. It is the grade most occasional-use stoves are lined with, and money saved here is not corner-cutting.
The condition is the fuel discipline: dry wood, sensible use, annual sweeping. A 316 liner treated to wet logs and rare sweeps ages fast, whatever the brochure said.
When 904 earns its cost
Three situations point to 904: a stove that runs daily through winter, a stove that is the primary heat source, and regular smokeless fuel use, whose condensates are the most acidic thing a flue meets. Rural homes off the gas grid around our patch often tick all three, which is why we specify 904 so often out toward the dales, moors and Wolds.
The arithmetic is simple: the price difference between the grades is small against the cost of relining twice. Hard-working flues buy the armour once.
How we specify yours
On the survey we ask how the stove will actually live: evenings or all day, treat or heating, wood only or smokeless reserve, and what the local fuel supply looks like. The answer sets the grade, the diameter comes from the stove, and both are written into the quote so you can see exactly what you are buying.
Common questions
Is a 904 liner always better than 316?
It is always tougher, not always necessary. For an evenings-and-weekends stove burning dry wood, 316 serves well for years and the extra spend is better put toward the stove or the hearth. We specify the grade to the use, not to the invoice.
How long does each liner grade last?
Honest answer: it depends more on use than grade. Well-treated 316 in occasional use gives many years of service; 904 in the same conditions lasts longer still, and in hard daily use the gap widens significantly. Dry wood and annual sweeping extend either.
Can I upgrade from 316 to 904 later?
Only by relining, which is why the grade decision is worth getting right first time. If there is any real chance the stove becomes your main heat, specify 904 at the start.
Does burning smokeless fuel really damage liners?
Its condensates are more acidic than wood smoke, so it works the liner harder, which is precisely what 904 grade exists for. A multi-fuel stove using smokeless fuel regularly should sit on a 904 liner.
What diameter liner does my stove need?
Whatever its manufacturer specifies, most commonly 125mm or 150mm on the stoves we fit. Undersizing a flue to save money ruins the draw and is one of the classic faults we are asked to put right.
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