Here's Why It Happens (And How to Fix It Fast)
Nothing ruins a cozy evening faster than smoke billowing back into your living room. If your fireplace is smoking you out instead of warming you up, you're dealing with downdraft—and it's more common than you think.
Downdraft (or backdraft) happens when air flows DOWN your chimney instead of UP. When this occurs, smoke from your fire gets pushed back into your room rather than safely exiting through the chimney.
Safety Warning: Downdraft isn't just annoying—it's dangerous. Carbon monoxide (CO) can also be pushed back into your home. If you're experiencing severe downdraft, stop using your fireplace immediately and get it inspected!
Identifying WHEN the smoke comes back helps pinpoint the cause. Tick which applies to you:
Likely cause: Cold chimney or need to "prime" the flue. Usually improves after 5-10 minutes.
Likely cause: Wind turbulence at chimney top, nearby tall structures, or missing/wrong cowl.
Likely cause: Not enough air in the room. Modern airtight homes need ventilation for fires.
Likely cause: Structural issue—blocked chimney, wrong height, or damaged flue.
Likely cause: Bird nest, debris buildup, or damper left closed. GET IT INSPECTED before using!
We've diagnosed hundreds of smoking chimneys across Essex and Hertfordshire. Here are the usual suspects—ranked by how often we see them:
Years of soot, creosote, and debris build up inside your chimney, reducing airflow. It's like trying to breathe through a blocked nose—the smoke has nowhere to go but back down.
Professional chimney sweep. A HETAS certified sweep will remove all blockages, soot, and creosote buildup. Takes 1-2 hours, costs £60-90, and solves the problem instantly in most cases.
Prevention: Sweep annually for occasional use, twice yearly for regular use (wood burners).
Modern homes are built airtight for energy efficiency. But fires need LOTS of air! If your room is sealed tight (double glazing, draft excluders, extractor fans running), there's not enough oxygen for combustion. The fire "steals" air from the only place it can—down the chimney.
Quick test: Open a window 1-2 inches when lighting fire. If smoke stops, you need more ventilation.
A cold chimney is full of cold, heavy air that doesn't want to move. When you light a fire underneath cold air, the smoke can't push past it initially. This is why smoke often billows back for the first 5-10 minutes, then clears.
"Prime" the chimney before lighting main fire:
Long-term fix: Insulate external chimneys or install a flue liner to keep chimney warmer.
Building regulations require chimneys to extend at least 1 meter above the roof ridge (highest point). Short chimneys don't create enough draft, and wind can easily push air back down.
Extend chimney height by adding chimney pots or extension sections. Target: 1m above ridge, or 2.3m above flat roof.
Cost: £200-600 depending on access and materials. Requires scaffolding and professional installation. Building regs inspection may be needed.
Strong winds can create turbulence at the chimney top, forcing air back down. This is especially common if you live near hills, tall buildings, or have trees close to your chimney.
Install anti-downdraft chimney cowl. These clever devices prevent wind from blowing down while still allowing smoke to escape. Different types for different problems:
Birds (especially jackdaws) LOVE nesting in chimneys during spring. A single nest can completely block airflow. Fallen bricks, leaves, or even dead birds can also obstruct the flue.
Professional removal ONLY. Under UK law, you CANNOT disturb active nests with eggs or chicks (£5,000 fine + criminal record). Wait until birds fledge (usually August), then have sweep remove nest.
Prevention: Install bird guard/cowl with mesh (£60-100). Must allow access for sweeping.
Many chimneys have a damper (metal plate) that closes the flue when not in use. If you forget to open it fully before lighting a fire, smoke has nowhere to go but back into your room!
Open the damper! Look for a lever, handle, or chain inside the fireplace. Push/pull it all the way open before lighting fire. When open, you should see daylight when looking up the chimney.
Tip: Tape a reminder note near fireplace: "DAMPER OPEN?" to avoid future mistakes.
Modern homes have multiple systems fighting for air: extractor fans, boilers, tumble dryers, bathroom fans. These can create negative pressure that literally sucks air (and smoke) down your chimney.
Don't use extractor fans when fire is burning. If you must use them, open a window to provide makeup air.
Permanent solution: Install passive air vents or mechanical ventilation with heat recovery (MVHR). This is complex—consult a HETAS engineer for assessment (£150-300).
Try these simple fixes before calling a professional:
Call a HETAS certified sweep if:
HETAS certification means the sweep has:
Book chimney sweep once yearly (twice for wood burners). This prevents 90% of downdraft issues before they start.
Install mesh cowl to prevent nests. One-time cost (£80-120) saves you £100+ annual bird nest removal.
Ensure room has adequate airflow. Crack window when using fire, or install permanent air vent near fireplace.
Wet wood creates more smoke and creosote. Use kiln-dried or seasoned wood (moisture below 20%).
Better to have small hot fire than large smoldering one. Hot fires create better draft and less creosote.
If problems persist, get camera survey (£80-150). Identifies cracks, damage, or structural issues.
A: YES. Smoke contains carbon monoxide (CO), an invisible, odorless gas that kills. If smoke is entering your room, CO is too. Don't use the fireplace until the problem is fixed. Install a CO alarm (£15-25) BEFORE using any fireplace.
A: Simple fixes (opening damper, opening window, priming cold chimney) you can do yourself. But if the problem persists, you NEED a professional. Chimneys are complex—what seems like a simple blockage could be structural damage or dangerous creosote buildup. A HETAS sweep costs £60-90 and provides peace of mind.
A: Depends on the cause. Chimney sweep (fixes 40% of cases): £60-90. Installing cowl: £100-200. Adding ventilation: £50-150. Extending chimney height: £300-800. CCTV survey to diagnose: £80-150. Most problems are fixed with a simple sweep!
A: This is "cold chimney" downdraft. The column of cold air inside needs warming before hot smoke can rise through it. Prime the chimney by holding lit newspaper up the flue for 30-60 seconds before lighting your main fire. This warms the air and establishes upward draft.
A: No, but it's a common misunderstanding! Blocked gutters cause damp and water damage but don't affect chimney draft. However, if you're booking a chimney sweep, ask about gutter cleaning too—we often offer both services together at a discount.
A: Common, but NOT normal! Wind shouldn't cause downdraft. This usually means: 1) Chimney is too short, 2) No anti-downdraft cowl installed, or 3) Nearby tall structures creating turbulence. An anti-downdraft cowl (£80-150 fitted) usually solves this completely.
A: ABSOLUTELY NOT! Get it inspected and swept first. In 5 years, birds could have nested, bricks could have fallen, water damage could have occurred, or deadly creosote could have solidified. Book a sweep with CCTV survey (£120-180 total) before burning anything. Your life depends on it.
Sweep Sisters are HETAS certified chimney sweeps serving Essex and Hertfordshire. We diagnose and fix downdraft problems fast—usually same or next day appointments available.
Certificate Issued • Fully Insured • Professional Equipment
Most downdraft problems are quick and inexpensive to fix. Whether it's a simple sweep, installing a cowl, or improving ventilation, we'll diagnose the issue and have you enjoying cozy fires again within days. Don't risk your family's health—get it sorted today.
