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What fails on a house, why it fails, and what it should cost

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Masonry, flues and venting

Chimney — problems, causes and costs

Most chimney damage is water getting in at the top, and most chimney danger is in the flue. Find what you’re seeing below. A couple of these you can handle yourself, and we say which ones.

877-360-4657What chimney work costs
Quick answerChimneys fail in two ways. Outside, water gets in through an open flue, a cracked crown, failed flashing or worn mortar, and freeze-thaw breaks the masonry apart. Inside, the flue stops venting safely: creosote builds up, an old flue has no liner, or a gas appliance is connected to a flue it doesn’t suit. The outside problems cost money. The inside problems can cost lives.

Everything we have on chimneys: what fails, why, what it costs, and which of it you can handle without calling anyone. NFPA 211, the national fire-safety standard for chimneys and vents, recommends having chimneys inspected once a year.

A red brick chimney stack rising above green tree branches against a pale sky
A red brick chimney stack. Most of the damage starts at the top, where water gets in. Photo by Phil Hearing on Unsplash.
Carbon monoxide alarm sounding?

Get everyone outside now and call 911 or the fire department from outside. Don’t go back in to investigate. See carbon monoxide alarm sounding.

1Start with what you can see

Often DIYNo cap on the flueAn open flue takes rain, birds and squirrels. A cap is inexpensive protection. Check the flashingStaining on the ceiling around the chimneyAlmost always flashing, the most common roof leak point on any house. Usually a proCracked crown at the topOnce the crown cracks, water gets into the masonry and freeze-thaw takes it apart. SafetyUnlined flue on an older chimneyA fire and carbon monoxide risk with a modern appliance. Relining is the standard fix. SafetyCreosote build-up in a wood-burning flueCreosote is what chimney fires burn. Annual inspection and sweeping isn’t optional. EmergencyCarbon monoxide alarm soundingGet everyone out, then call 911 or the fire department from outside. Catch it earlySpalling brick on the exterior stackFlaking face brick means water is getting in and freezing. Tuckpointing early helps. SafetyGas appliance venting into an old flueAn oversized flue can stop a gas appliance drafting properly. That’s a venting assessment. CostsChimney cost: what to expect and what to skipWhat drives the price, and which chimney work you shouldn’t be paying for.

2How chimneys fail

FailureUsual causeFirst thing to do
Leak at the ceilingFailed flashing where the chimney meets the roofHave the flashing checked before blaming the masonry
Water inside the flueNo cap, or a cracked crownAdd a cap; have the crown inspected
Crumbling brick and mortarWater in the masonry freezing and thawingStop the water at the top, then repoint
Chimney fire riskCreosote build-up from wood burningAnnual inspection, and sweeping when needed
Poor venting or CO riskUnlined flue, or a gas appliance on a flue that doesn’t suit itHave the flue and venting assessed by a qualified pro
A chimney sweep at work, sitting on a roof
A chimney sweep at work on a roof. A yearly inspection catches flue problems before they become dangerous. Photo by Waldemar Brandt on Unsplash.
Not a DIY job

Don’t attempt your own work on flue liners or gas appliance venting. Mistakes there can let carbon monoxide into the house.

Chimney leaking, crumbling or overdue for an inspection?Talk to a local chimney pro who will check the flashing, crown and flue, not just the bricks you can see.
877-360-4657

3What chimney work costs

The price moves with roof height and pitch, how much of the stack is affected, whether the work is flashing, crown, masonry or flue, and whether scaffolding or a lift is needed. Relining a flue is a larger job than sweeping one. Prices vary by region, and where a job has a genuine do-it-yourself version we say so rather than quoting a number.

Chimney cost: what to expect and what to skip

4Chimney FAQ

How often should a chimney be inspected?

NFPA 211 recommends an inspection once a year, and sweeping when the inspection shows it’s needed. Regularly used wood-burning appliances need it most.

Why is my ceiling stained next to the chimney?

Almost always failed flashing where the chimney meets the roof, not the masonry. Have the flashing checked first.

Do I need a chimney cap?

An open flue lets in rain, birds and animals. A cap is inexpensive and prevents most of the moisture damage that later costs real money.

Can I connect a new gas appliance to my old chimney?

Not without a venting assessment. A flue sized for a wood fire is often oversized for a modern gas appliance and may not draft properly. Leave this to a qualified pro.

Written by Jaylan Jones. I Like To Exterior Services earns a referral fee when a call connects to a contractor. See our business-model disclosure.

877-360-4657