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Installing a Flue Through a Pitched Roof
Published on 6 August 2026
Written by Dries Nijs4 min read
Written by Dries Nijs4 min readInstalling a flue through a pitched roof without leaks
You install a flue through a pitched roof using a certified roof flashing, a lead flashing or storm collar, and a termination high enough above the ridge. The flashing keeps the roof tiles watertight, while the ridge rule determines the termination height.
The further from the ridge, the higher the termination must rise above the roof surface.
You install a flue through a pitched roof using a certified roof flashing matched to the roof pitch, supplemented with a lead flashing or universal tile flashing, a storm collar, and a termination that rises high enough above the ridge. The flashing creates a watertight seal among the roof tiles around the double-wall stainless steel flue. The termination height follows the ridge rule, depending on the distance to the ridge. This keeps the penetration leak-free and the draft stable.
Termination close to the ridge or far from the ridge
As a rule of thumb, the further the penetration is from the ridge, the higher the termination must rise above the roof surface.
Correct termination height
We match the termination to your roof pitch and distance to the ridge. This ensures a stable draft and less smoke nuisance.
Advice when in doubt
With a difficult pitch or tile type, we think along with you. You receive honest advice on whether to do it yourself or have it installed.
How to install a flue through a pitched roof step by step
Determine the passage location as close to the ridge as possible, as this reduces the required height and improves the draft.
Choose a roof flashing that matches your roof pitch and tile type, or use a universal flashing with a lead skirt.
Remove the tiles at the passage location and make a neat opening in the roof boarding and underlayment.
Slide the double-wall stainless steel flue through the opening, maintaining the prescribed clearance from combustible parts at all times.
Place the roof flashing or lead skirt watertight over the surrounding tiles and finish the connection neatly.
Install the storm collar around the flue, which seals the passage against driving rain and meltwater.
Continue building the double-wall flue above the roof to the correct discharge height and secure it with brackets.
Finish with a suitable rain cap and then check the draft and the tightness of the passage.
Checklist for a leak-free roof passage
Roof flashing is certified and matched to the correct roof pitch
Lead skirt or storm collar fits tightly and watertight around the flue
Discharge height corresponds with the distance to the ridge
Prescribed clearance to wooden roof parts and insulation is respected
Flue above the roof is double-walled and secured with brackets
Underlayment is neatly folded back to prevent condensation and ingress
Waterproofing, clearance to the roof surface and insulation
The waterproofing around the tiles is the most sensitive point when installing a flue through a tiled roof. A roof flashing or lead skirt drains rainwater over the tiles, while the storm collar seals the final gap around the flue. If you work with a universal tile flashing, you must bend the lead tightly around the surrounding tiles.
Preferably choose a roof flashing that exactly matches your tile type, such as an interlocking clay tile or a concrete roof tile. A tile that does not quite fit forces you to do cut-and-paste work that leaks more easily. A universal tile flashing is a good alternative for less common tile types.
Above the roof, you continue building with a double-wall system so the flue gases remain warm and the draft stays optimal. A double-wall flue cools down less quickly, resulting in less condensation and soot buildup. Inside the roof, maintain the specified clearance to wooden parts and insulation. You can read more about this in our guide on the clearance to combustible materials for stove pipes.
In the attic, the flue often passes through the insulation and the underlayment. Use a ventilated firestop or insulation passage there, so the heat from the flue does not come into contact with breathable foil or mineral wool. This keeps the passage safe and dry.
The draft depends on the total height and the number of bends. The straighter and higher the flue above the roof, the better the flue gas extraction. Therefore, stay as close to the ridge as possible and limit the number of bends in the vertical section.
If you want to understand which parts make up a roof passage first, take a look at how exactly a roof passage for a flue works. An incorrect discharge height or poor sealing are among the classic issues, as you can see in our post about common mistakes with flues.
Regulations in Belgium and the Netherlands
The exact requirements for the discharge and roof passage differ per region and municipality in Belgium, and per municipality in the Netherlands. In Belgium, the NBN standards serve as a practical framework, but your municipality, the manufacturer's manual, and your fire insurer help determine what is binding. Always check the regulations before you start.
Also pay attention to the distance to roof windows, dormers, and the property line. A discharge too close to a window can cause smoke nuisance, and some municipalities set extra requirements for this. In addition, the manufacturer often prescribes a minimum clearance to combustible roof parts, which you must strictly observe.
A pitched roof is not always the only route. If you are doubting between the roof and the facade, weigh the pros and cons of a flue through the roof or through the wall. For a different roof situation, our guide on installing a flue through a flat roof will help you with the differences in discharge and sealing. For a complex pitch, a breathable underlayment, or a difficult tile type, it is better to call in a professional.
Are you unsure about the discharge height, the roof pitch, or the right roof flashing for your home? Request a free quote or advice, and we will look at your roof situation together with you.
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Frequently asked questions
For a penetration close to the ridge, the termination typically rises above the ridge. If the penetration is further away, a minimum height above the roof surface often applies, measured within a certain distance. Check the exact requirements with your local municipality and the manual.
For a tiled roof flue, you use a roof flashing matched to your roof pitch and tile type, or a universal tile flashing with lead flashing. A storm collar seals the final gap around the flue against driving rain.
You can install a pitched roof penetration yourself if the pitch is simple and you ensure good sealing, provided you maintain clearances to combustible materials. For a steep pitch, vapor-permeable underlayment, or difficult tile type, it is better to hire a professional.
A roof penetration usually leaks due to poorly connected lead flashing or a missing storm collar. A mismatched roof flashing or a sloppy cutout in the underlayment foil can also let water through. A tight, watertight finish around the tiles prevents this.
