How to Remove an Old Chimney Above the Roofline and Roof Over the Opening
Only for a chimney that is truly out of service. Permits, venting and hazardous materials come before any demolition.
- Professional
- 1 to 3 days
- Updated
The short answer
To remove an unused chimney and roof over it, first confirm that no appliance vents through it, check permit requirements and test for hazardous materials. Take the masonry down below the roof deck, frame the opening with headers and trimmers sized to the rafters, sheath it, lay ice and water shield and underlayment, and shingle over. A chimney still in use must never be removed or capped.
Old chimneys are often left standing long after the fireplace or furnace that used them is gone. They leak, they need repointing and flashing, and they sit on the roof as a maintenance job for no benefit. Taking the part above the roofline down and roofing over the opening removes the source of the leak for good.
Before anything is touched, there are questions that matter more than the roofing. Is the chimney still in use? A chimney still serving a furnace, water heater, wood stove or fireplace must never be removed or capped. Gas and solid-fuel appliances vent through their chimneys, and blocking or removing the vent can cause carbon monoxide to enter the house. Permits, appliance venting and hazardous materials are all involved. This guide covers the roof side once those are cleared. For leaks on a chimney you are keeping, see how to diagnose and fix a leaking chimney.
Tools
- Masonry demolition tools
- Safety glasses, hearing protection and a respirator for silica dust
- Framing square and saw
- Tape measure
- Chalk line
- Roofing hammer or nailer
- Shop vacuum
- Debris chute or lowering rope system
Materials
- Dimensional lumber matching the rafter size for headers and trimmers
- Joist hangers and framing nails
- Plywood sheathing matching the roof deck thickness
- Ice and water shield
- Underlayment
- Shingles to match the roof
- Roofing nails, 1-1/4 inch
Safety first
- Work tied off. Demolition at the ridge side, on a roof with debris underfoot, is a fall hazard. WorkSafeBC requires fall protection at 3 metres (about 10 feet) and wherever a fall could cause serious injury.
- Older chimneys can contain asbestos in flue liners, cement and insulation, and lead paint on nearby materials. WorkSafeBC requires hazardous materials to be identified before workers demolish or renovate, and it treats buildings from before 1990 as likely to contain asbestos. Do not disturb suspect material before it has been tested.
- Brick and mortar dust contains silica. Use dust control and a respirator, and keep people clear of the drop zone below.
Step by Step
Step 1: Confirm the chimney is out of service
Trace every appliance vent in the house. A masonry chimney often serves more than one floor, and a flue can serve a gas water heater in the basement even when the fireplace upstairs is long disused. If any appliance vents into it, or you are not sure, stop. Have a licensed gas fitter or a WETT certified technician confirm, and arrange alternative venting before removal. Never cap or block a flue in use.
Watch out: Removing or capping a chimney that still vents an appliance can fill the home with carbon monoxide.
Step 2: Check permits and regulations
Most municipalities in BC require a building permit for removing a chimney, particularly where framing is altered or the chimney passes through the structure. If gas appliances are involved, FortisBC and a licensed gas fitter are part of the job. Strata and heritage properties may have further rules. Ask your local building department what is needed before starting.
Step 3: Test for hazardous materials
Houses built before the 1990s may contain asbestos in flue cement, transite pipe and some insulation products, and lead in old paint on trim and flashing. WorkSafeBC requires hazardous materials to be identified by a qualified person before workers demolish or renovate, and even if you are doing the work yourself, the test is the only way to know. Do not disturb suspect material until a lab has tested it. Dust and debris from a chimney are also silica hazards.
Step 4: Take the chimney down from the top, in controlled sections
Work from the top down, course by course, and never undermine the masonry from the bottom. Drop no loose brick on the roof. Use a debris chute or lowering system into a bin, and keep the area below clear. Take the masonry down to below the roof deck, usually to the attic floor or a convenient point, so that the framing can be closed above it.
Remove the old flashing at the same time, down to bare deck. See how to tear off a shingle roof.
Step 5: Check the structure around the opening
Chimneys in old houses sometimes have rafters or joists cut to go around them, and some are built into the structure. Check the framing under the roof, and if any structural member was cut, have the repair assessed by an engineer or the building department. If the chimney continues down through the house, removing only the part above the roof leaves the rest in place, and that also needs a plan. Do not remove any masonry that supports floors or roof framing without advice.
Step 6: Frame the opening
If rafters were cut for the chimney, restore them with doubled headers and trimmers, using lumber the same depth as the rafters and joist hangers or approved connections. Span the gap with framing so the deck can be continuous. Where the old chimney opening was sized to maintain a code clearance from masonry, the framing no longer needs it, but follow the local building department's requirements and inspection.
Step 7: Sheathe the opening and tie it into the deck
Cut the plywood so its edges fall on framing and stagger seams with the existing deck where possible. Nail at the same spacing as the rest of the roof. The patch should be flush with the surrounding deck. See how to replace roof sheathing.
Step 8: Waterproof and shingle over the patch
Apply membrane across the patch and its edges, lapping onto the existing deck. Then lay underlayment and shingle courses, weaving the new shingles into the existing courses so no seam runs straight up the roof. See how to tie in new shingles and how to install ice and water shield.
Step 9: Deal with the chimney below the roof
If the masonry remains below the roof, it should be capped and sealed at the top in the attic, and any openings at the ceiling or fireplace closed properly, with the local building department's guidance. Removing it fully is a larger demolition job with its own structural and permit considerations.
A Chimney in Use Must Not Be Removed or Capped
This cannot be stressed enough. A chimney that vents a furnace, boiler, water heater, wood stove or fireplace is part of a safety system. Taking it away or capping it, even partly, can back combustion gases and carbon monoxide into the house. If you are not certain nothing vents into it, have a licensed gas fitter or WETT certified technician check before any demolition.
Why Remove It at All
An unused chimney is a maintenance item that still leaks: the flashing, crown, cap and masonry all need attention. Removing the chimney above the roofline eliminates that leak path, frees the roof for a simpler layout and removes a heavy, sometimes leaning, mass above the living space. The trade-off is the cost and the permits, and a chimney may matter for resale or heritage value, so confirm before you start.
Common Mistakes
- Removing or capping a chimney still in use. Combustion gases and carbon monoxide can back up into the house.
- Skipping the permit. Unpermitted structural work causes problems at resale and with insurance.
- Skipping the hazardous materials test. Asbestos and lead in an old chimney assembly are serious hazards when disturbed.
- Undermining masonry from the bottom. Demolish from the top down, in controlled sections.
- Cutting structural members without advice. Some chimneys carry framing.
- Patching the deck without proper framing. Plywood edges that fall between framing members sag and crack.
- Shingling the patch as a square. Tie it in with staggered courses, so there is no straight seam up the roof.
When to Call a Professional
Chimney removal combines masonry demolition, structural framing, roofing, hazardous materials and, often, gas or solid-fuel appliance venting. Use a contractor for the demolition and roofing, a licensed gas fitter or WETT technician for the venting, and an engineer if the chimney is part of the structure. Always arrange the permit first.
If the chimney still serves any appliance, the answer is not to remove it, but to repair or reflash it. See how to reflash a chimney during a reroof.
Fraser Roofing does free roof inspections across the Fraser Valley, from Hope to Abbotsford. See our Roof Repair service or the towns we cover.
How to Remove an Old Chimney and Roof Over It: Questions
Can you remove a chimney and roof over it?
Yes, if the chimney is no longer in use. The masonry above the roofline is taken down to below the deck, the opening is framed with headers and trimmers, sheathed, covered with ice and water shield and underlayment, and shingled to match the rest of the roof. A chimney that still vents any appliance must never be removed or capped.
Do you need a permit to remove a chimney in BC?
Most municipalities require a building permit for removing a chimney, particularly when framing is altered, and gas appliance venting involves a licensed gas fitter. Rules vary by city and district, so ask your local building department before you start. Strata and heritage properties can have additional requirements.
Is it safe to remove an old chimney myself?
It is usually a job for contractors. Old chimneys can contain asbestos in flue cement or insulation, produce silica dust, and may carry structural load. Demolition at the ridge also carries fall risk. A hazardous materials survey, a permit and confirmation that no appliance vents into the chimney should all come before any demolition.
What happens to the chimney below the roof after removal?
If only the part above the roofline is removed, the rest stays in the house and should be capped and sealed at the top in the attic, with openings at the ceiling or fireplace closed properly as the building department directs. Removing the whole chimney is a larger structural job and needs its own plan and permit.
Will removing a chimney stop a roof leak?
It removes the chimney as a leak source, since there is no more flashing, crown or masonry to fail. The roofed-over opening must be framed, sheathed, waterproofed and shingled properly to be watertight. If the leak actually came from elsewhere on the roof, removing the chimney will not fix it, so confirm the source first.
Related Guides
All Chimneys guides|The full How-To Library
This guide is general education. Always follow the product manufacturer's installation instructions, the BC Building Code and WorkSafeBC requirements, which take priority over anything written here.
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