Chimney Maintenance and Repair Costs: Chimney Flashing, Spalling

While the chimney is often ignored, it’s actually one of the most important structures of your home. Both its exterior and interior should be maintained.

Many people forget that the fireplace is only as good as the chimney above it. The moment you realize that your chimney is not working as well as it should, you must take action to have it fixed.

After all, a faulty chimney will not only negatively affect your fireplace, but it also compromises your safety. Being proactive beats being reactive. Keeping the chimney in good condition now will save you from costly repairs in the future, and might save your life.

The general rule is to have your chimney inspected and cleaned at least once a year. However, that doesn’t mean you should ignore your chimney in between inspections. You need to always be on the lookout for potential problems with your chimney to avoid costly repairs and to prolong its lifespan.

Being knowledgeable about the parts of a chimney will help you identify problems. Here’s an overview.

Chimney Exterior

The exterior of your chimney is not just for appearance. It has many essential parts that contribute to the safety and performance of your chimney and fireplace.

The Bricks

The bricks are not only the facade, they provide stability to the chimney stack and allow for the performance of your fireplace. If the bricks are damaged, there’s the risk of water seeping into the cracks and freezing then thawing with temperature changes. This will cause spalling.

Brick chimney spalling

Spalling is deterioration of the mortar between the bricks causing the mortar to crack, crumble and fall out. Spalling will eventually cause the brick facade to become weak and the individual bricks to become loose.

Chimney Crown

Chimney crown repair before and after
via The Chimney Guy

Often mistaken for the cap, the chimney crown is a slab of concrete that covers the edges of your chimney’s opening. Its main function is to provide a barrier between the top of the chimney and the outside elements.


Chimney Cap

Chimney cap flashing before and after
via Done Right Roofing

The chimney cap is a protective shield placed over the entire top of the chimney, preventing external elements like rain, snow, debris, and animals from invading the interior of the chimney. They also keep hot embers from the fireplace catching your roof on fire. Some chimney caps have wiring or grating around them as a second line of defense.

Chimney Flashing

Copper flashing around brick chimney on an asphalt roof
via Runyon and Sons Roofing

The chimney flashing is a protective coating placed in the area where the chimney meets the roof therefore preventing moisture from entering your attic or home’s interior.

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Chimney Interior

Problems with the exterior can lead to damage over time. When the interior of your chimney fails, the damage can be swift and unexpected.

Chimney Flue

The chimney flue is the passageway through which the smoke from the fireplace will exit your home.

Chimney Flue Liner

The chimney flue liner is the material that covers the inside walls of the flue. Its main function is to facilitate the safe and efficient passage of smoke through the flue and out of the chimney’s mouth. It protects your home from the high temperatures produced in the fireplace. A chimney without a liner can be dangerous, since there is the risk of high temperatures, as well as, toxic gases, billowing back into your home.

Throat Damper

The throat damper controls the air flow in and out of your chimney. The throat damper should be closed when you aren’t using your fireplace to prevent cold air from entering, and open, when the fireplace is being used, to allow the smoke to exit.

Fire Box

The fire box is the part of your fireplace where the fire is built. Masonry fireplaces typically have brick fire boxes.

Smoke Chamber or Smoke Shelf

The smoke chamber is the area between your firebox and the flue. This chamber compresses the smoke and combustible material so they pass through the flue without allowing a back draft.

Soot and creosote gather inside the smoke chamber, which is why it must be cleaned and inspected regularly.

Chimney Inspection

While you can inspect your chimney, consider having an experienced professional inspect your chimney once a year to look for defects you might miss.

Professionals will use video cameras and other equipment making it possible for them to find issues that are not visible to the average homeowner.

Signs of a Damaged Chimney and How to Fix Them

The signs of a damaged chimney or fireplace aren’t always obvious, and early detection is important to preventing high repair costs later.

Note: Most chimney maintenance covers only the outside of the chimney. We start here and work our way inside.

Efflorescence

Chimney efflorescence
via A1 Quality Chimney

Efflorescence, which means “flowering,” is white staining that appears on your chimney’s brickwork. The stain itself is not a problem and can be easily removed. But it is a sign that your chimney has a moisture problem. Moisture is a byproduct of combustion.

Efflorescence shows that the moisture is seeping from the inside of the chimney outward, dissolving salts in the mortar and bringing them to the surface of the exterior. If ignored, the moisture will cause your chimney to deteriorate. Stopping the issue is addressed below.

Removing Efflorescence:

Here are common ways to remove the stains:

  • Power Washing

This method works for cleaning the masonry of surface deposits but keep the pressure under 1,200 psi to avoid damaging the brickwork.

  • Sandblasting

Sandblasting works well if you know how to apply just the right amount of pressure. If you use too much pressure, the masonry could become more porous, making the surface more susceptible to efflorescence. To avoid this problem, apply sealant to the surface when you’re done.

  • Chemicals

If the white stains are not coming off with the above methods, then chemical cleaning is needed. There are many approved commercial cleaning agents available. A cheap alternative is to use organic acids such as vinegar, citric acid, or tartaric acid.

Cost

The cost of removing efflorescence varies depending on the method used. Sandblasting will cost between $30 to $75 an hour, not including the cost of the materials which should run around $50. If power washing is used, expect to pay a contractor a rate of 15 to 40 cents per square foot.

Cracked or Melted Crown

The crown is the first line of defense against external elements. If it is cracked or melted, moisture will seep in and deteriorate the mortar, further widening the cracks.

Fixing a Cracked or Melted Crown

If the damage is not too severe, you can fill the cracks with a thoroughly mixed thinset mortar. Apply it to the cracks until they are filled, and then smooth the mortar by pressing a thin piece of wood against the wet mortar.

Chimney crown repair and waterproofing with CrownSeal

Another solution is to caulk up the cracks. First remove any loose or crumbling mortar from the cracks. Apply the caulk to the cracks, and smooth the edges with a thin, stiff brush. Make sure you are getting the caulk deep into the cracks, then wipe away the excess mortar with a brush or wet rag. Whichever method used, apply an waterproof elastomeric coating after repairing the cracks.


Cost

Small cracks shouldn’t cost much, perhaps $175 to $250 to repair. If the cracks are large enough that bricks must be removed and reset, the cost will likely be between $650 and $1,000 depending on the extent of the repair.

Spalling Bricks

Spalling happens when moisture penetrates your chimney’s masonry or the bricks, causing it to crumble and lose its structural integrity. It progresses more rapidly in freezing climates because moisture freezes and expands in the cracks, widening them. Spalling should be addressed immediately.

First, address the source of the problem – the moisture. Check the flue and the masonry to find how the moisture is getting in. Once the source is determined, the appropriate treatment should be performed.

Early Stage Spalling

Early stage spalling usually involves small cracks in the brickwork or mortar. They can be repaired by applying a waterproof sealant.

Late Stage Spalling

Late stage spalling usually involves severe deterioration of the chimneys brickwork. In this case, heavy treatment is required. You will need to replace bricks and mortar joints.

If the spalling has come to the point where the chimney structure is drastically compromised, the only choice may be to rebuild the chimney or install a new one. If the chimney is rebuilt, the contractor should apply a waterproofing sealant with a cap sealer to ensure that the fresh masonry is reinforced. In most cases, a new chimney cap must be installed.

Cost

The repair costs depend on the severity of the issues. At the early stages, expect to pay a contractor between $900 and $1,200. Spalling at an advanced stage may cost $3,000 or more.

The materials for a DIY repair will cost between $275 and $400 in most cases.

Deteriorating Mortar Joints

Mortar joints hold your brickwork together. If they are cracked, moisture can easily find its way into your chimney causing further damage. Check for cracks and repair the mortar joints as soon as the cracks are visible.

Fixing Deteriorating Mortar Joints

Repairing mortar joints involves two processes called tuck point or repoint – removing the crumbling mortar and then reapplying new mortar into the gaps.

Both of these processes require precision. The old mortar must be removed to a depth of 3/4 inches. The new mortar will be inserted to fill the gaps. If you tackle the work, read the bag to ensure the mortar you choose for the work is designed for tuck pointing.

Costs

If you are dealing with a few small cracks, the cost of repair would be about $150 to $250. Severe cases could require a rebuilding of the entire chimney facade and sidings, which could cost $3,000 or more. This is labor-intensive work, so if you do it, you’ll save 75% or more of the cost of hiring a pro.

Internal Maintenance and Repair

Here are important issues to look for and address inside the chimney:

Shaling Clay Flue Liner Tiles

If you start to see thin slices of chimney tiles in the fireplace, then your flue liner is probably cracked and shedding material. Flue liners help keep extreme heat away from combustible areas of your home. A cracked flue liner is a fire hazard and needs to be addressed. Even a small crack can allow creosote, carbon monoxide and other harmful chemicals to enter your home. It can also lead to an efflorescence problem.

Inspecting the Clay Flue Liner Tiles

If you can safely stand on your roof, look into the chimney and inspect the upper sections of the clay tiles for damage. Take a flashlight with you.

You won’t be able to reach very far down into the chimney, but checking the top one or two tiles will give you a good idea if there are any problems, since these are usually the first to have issues. This is because they are at the top of the chimney where moisture caused by combustion is likely to condense when it meets cool outside air. Moisture is the nemesis – even in a fireplace.

First, check the mortar joints between each section of tile, looking for missing or cracked mortar. Second, check the tiles themselves for breaks or cracks. And third, check the tiles for shaling. If this kind of flaking has occurred, the tiles will look rough or pitted instead of smooth and flat.

Fixing Shaling Clay Flue Liner Tiles

If you only have minor damage to the top portion of the flue, you should be able to fix it yourself. You can fill the cracks in the flue liner with a sealant, but this is only a temporary fix, as sealed flue liners will likely crack again.

If your flue liner is severely cracked or damaged, or you see shaling further down the chimney, you will need to contact a professional. For a severely damaged flue liner, the best course of action is to replace it entirely.

A stainless steel chimney flue liner is a popular option and will provide better durability. Most are backed with a lifetime warranty. You can purchase either a rigid or flexible liner. Flexible liners will expand and contract better allowing buildup to flake away and not adhere to the liner walls.

Another possible option would be the cast-in-place method of replacing the flue liner. This is not a do-it-yourself project because the process requires special equipment to create a liner that is a custom fit for your chimney.

The process includes putting an inflatable mold or bladder down the chimney, placing spacers between the existing flue liner and the bladder, inflating the bladder, and then pumping cement into that space. Once the cement is dry, the bladder is deflated and removed leaving behind a new flue liner.

Costs

The costs for repairing shaling flue tiles will vary according to the severity of the problem and the materials used. Stainless steel liners generally cost between $50 to $75 per foot, but factoring in fees for labor and installation will raise the cost to between $90 and $115 per foot.

Creosote Buildup

Smoke is un-burned fuel that contains solids. When you have a fire, most of the smoke will be successfully vented. But some of it will settle back down. The solids can coat the chimney flue liner to form highly flammable creosote. This substance catching fire is the main source of chimney fires.

Removing Creosote Buildup

Creosote removal should be performed at least once a year. The right treatment depends on the severity of the buildup. The most popular method is a chemical treatment, which involves the direct application of a liquid spray, or anti-creosote powder onto the fire or firewood. When the fire is burning in the fireplace, the updraft causes the chemicals to stick to the creosote and convert it into harmless ash. The ash can then be removed with a chimney sweep brush.

Costs

A regular chimney sweep will cost between $140 and $350, depending on the type of chimney and its condition. Creosote removal will be costlier, since it requires the use of special chemicals or equipment and significantly more labor. You can also buy creosote logs (logs chemically altered to loosen creosote) for about $10 to $25 each. Their effectiveness is questionable when the creosote is heavy.

Rusted Firebox or Throat Damper

If the damper has a large amount of rust, it will be difficult or impossible to open or close, creating safety issues. You can remove rust by vigorously scrubbing it with a wire brush. Rust is toxic so wear safety goggles, gloves and a hat.

Cost

Expect to pay a contractor between $200 to $350 to have your firebox or throat damper cleaned. The labor costs will go up if the mortar needs to be removed before the rusted damper or firebox can be cleaned.


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