How to Flash a Chimney?

A chimney is an essential part of any fireplace or wood stove. It provides a way to vent the smoke that comes from burning wood in order to avoid toxic fumes in your home. It also helps control how quickly the fire burns, which can help you save money on fuel costs. However, it’s important to make sure your chimney stays clean and clear of obstructions so it can do its job properly! In this article, we will discuss how to flash a chimney correctly so you are able enjoy years of use out of yours!

Before you get started with the flashing process, there are a few things that need to be done in order for your chimney to be safe. The first thing is that the damper must be closed and in place. This will stop any debris from getting into the flue while you work on it. Secondly, if there is no metal cover plate over the top of the chimney, then one needs to be installed before continuing on with this project since it will help keep rain water out of your home.chimney sweep

What is the history of Chimneys and why do they need to be Flashed?

Chimneys were first used during the 12th century and since then, there is no point in time where they have not been an important part of our homes.

However, like any other architectural feature, over a period of time chimneys develop cracks and blisters that can decrease their durability as well as appearance. These are signs of flashing failure.

Flashing is a material that covers the joints between two separate components to prevent water from entering into it. As chimneys are made up of many parts, they need to be flashed correctly in order for them to function properly and last longer.

The components of a chimney include:

  • Flashings.
  • Chimney Crowns (the top most part).
  • Lintels or Jamb Liners (above doors and windows in the wall, protecting them from fire). These can develop cracks which need to be sealed.

Flashing is applied on various other parts of the chimney as well, including:

  • Chimneys over roofs.
  • Flashing can also be used to protect pipes passing through walls when they are connected to a flue system for ventilation purposes.
  • If you have noticed any cracks or blisters on your chimney it is important that you repair them right away. If you wait, the damage can become worse and more repair work will be needed.
  • Cracks can expand over time which would require a full replacement of the chimney rather than a simple repair job. This also means that it is going to cost you much more money in repairs compared to what they would have if done immediately.

Types of Flashing materials

  • Metal flashing is a thin piece of sheet metal that comes in rolls. It’s typically used on flat surfaces, such as roofs and chimneys. For shingled roofs, you can use rolled roofing underlayment instead of metal flashing because it offers the same protection against leaks but will better conform to curved surfaces around vent pipes or chimneys. Underlayment is made to be cut when necessary so it can easily fit the shape of your roof or chimney structure, and it’s applied in much the same way as rolled flashing.
  • Tar paper is a heavy duty material that comes in rolls just like metal flashing does. It’s typically used for covering roofs, but it can also be used to seal joints where roofs meet walls or other structures. Tar paper is available in two types, fiberglass and asphalt impregnated felt. Both are made of durable building materials that will hold up well against the elements for several years at a time, but you’ll want to make sure it’s properly secured so it doesn’t cause problems for you down the road.
  • Rubberized roofing cement is a sealant that’s typically used to help waterproof roofs and protect against leaks. It comes in buckets or tubs like paint does, but it can be difficult to work with unless you’re using an applicator gun because its consistency is thicker than most other types of roofing sealant. It’s a good choice for sealing seams, but it won’t work well as flashing material because of its thickness and the fact that you’d have to apply it in thick layers over entire surfaces to achieve maximum protection from water damage.
  • Foam board is an insulation product typically used beneath shingles or other types of roofing materials to help protect against heat loss and save on energy bills. It’s made of polystyrene foam that’s been sandwiched between two layers of paper, making it a good choice for insulating walls or roofs because its thickness can be cut down to size so you’ll have an easier time fitting the material around your chimney.
  • Rubber membrane is a rubberized material that’s typically used for waterproofing flat surfaces, such as decks or concrete patios. When it comes to protecting your roof against leaks caused by ice dams or other problems related to snow buildup, though, you’ll need something more durable than rubber membrane because the weight of an entire winter’s worth of snow would likely cause the material to tear.
  • Housewrap is a moisture barrier typically used beneath shingles or other types of roofing materials because it prevents water from penetrating through walls and causing leaks in your ceiling. It’s available in rolls, but you can also buy pre-cut pieces that are designed specifically for use around chimneys or other protrusions in your roof so you won’t have to spend time measuring and cutting the material down for a perfect fit.
  • Caulk is perhaps the most common type of flashing material because it comes in various forms that are very easy to apply, including tubes that can be squeezed out like toothpaste onto surfaces you want to seal. It’s typically used for sealing around roofing materials, but it can also be used on concrete surfaces where you need a durable rubber-like material that will prevent water from seeping through cracks or other openings in your home.
See also
How to vent a Wood Stove?

How to measure your Chimney for Flashing material?

Measure from the bottom of your chimney to its top. Take this measurement and add between 12-24 inches, depending on where you live and if there is a roof or gutter above it. This will be how much material you need for flashing a chimney.

What are the different types of Flashing Material for a Chimney?

If you have an older home with masonry chimneys, it is likely that your flashing material has deteriorated over time. Most commonly this comes in the form of corroded metal flashings which can be replaced by new ones.

Other materials to use include sheet metal, sheet rubber or lead.

What is the easiest way to Flash a Chimney?

The best way to do it is by hiring someone with experience, as flashing chimneys can be quite tricky and dangerous if not done correctly. There are videos available on YouTube which outline how this process should be performed. If you want to attempt it yourself, you should ideally have some experience or training of working with roofs.

The easiest way to Flash a Chimney?

The best way to do it is by hiring someone with experience, as flashing chimneys can be quite tricky and dangerous if not done correctly. There are videos available on YouTube which outline how this process should be performed. If you want to attempt it yourself, you should ideally have some experience or training of working with roofs.

What are the Tools needed for this Project?

The tools you need are a screwdriver, pliers and gloves. You also might want to have safety goggles or glasses on hand too in case of debris falling down from the chimney while you are flashing it with caulk.

  • There are several types of flashing kits available in the market. These usually contain self-adhesive waterproof materials that can be used to seal metal, wood or masonry surfaces like chimneys and roofs.
  • The kits also consist of stainless steel screws that are used for mounting the flashing.
  • You also might want to have a utility knife on hand in case you have to cut the flashing material.

How to install a new Chimney Cap?

In order to install a new chimney cap, you should follow the proper procedures. First of all, make sure that you have purchased a high-quality mesh screen and made it fit with your top plate perfectly. Then, apply some sealant/putty around the edge for extra protection from animals or insects trying to enter through your chimney.

Once you have applied the sealant/putty, fit your chimney cap in place and fasten it with screws or nails. You can also add some weather stripping around its edge to ensure a good seal against wind and rain. While doing so, make sure that the flange is placed well below the top plate for proper sealing.

See also
How to repair a Chimney Flashing?

Now, you can apply a layer of sealant/putty over the screws or nails to ensure an airtight fit and finish off your new chimney cap installation.

Install screen mesh on the chimney top plate, seal around the edge of the cap with some putty/sealant and then fit it in place tightly. Finish off by applying more sealant over screws or nails for an airtight finish.

Why it is important to have a tight seal on the top of your Chimney?

  • A) The top of the chimney is exposed to harsh weather conditions and it usually gets moisture. This allows for a buildup of moss, mildew, algae and mold inside your chimney walls. All these growths can reduce the life span of your Chimneys significantly. Cleaning or replacing them will cost you more money than having all the materials and tools needed to flash your chimney.
  • B) Allowing moisture into the top of your Chimneys will also allow water vapor to travel down (into the house). This may cause humidity problems such as condensation on windows, peeling paint, damage wood flooring or an increase in respiratory issues for people with asthma or allergies.
  • C) Lastly, water vapor will travel down and condense in the colder parts of your house. This can lead to a very high electric bill. That is because the humidity makes it feel warmer inside, so people tend to use their heating systems more often which consequently increases electricity usage.chimney

Environmental Protection Through Chimney Flashing

As required by the EPA, all chimneys must be flashed with aluminum or stainless steel to prevent water penetration. The flashing will protect your home from mold and mildew growth caused by moisture penetrating into the shell of your house through an un-flashed exterior wall of a home. Flashing will also help prevent water damage to your interior walls and ceilings.

This is a very important part of home maintenance that must not be overlooked by homeowners, especially those who live in cold climates where winter snow melts into the wall cavities which can lead to mold growth during warmer months. If you’re concerned about chimney flashing or just want to make sure it’s done right, you should consider hiring a professional chimney sweep service.

Safety Tips

  • Never go on the roof without a partner.
  • Wear safety gear, including gloves and boots with steel toes/toecap. Alternatively, use rubber overshoes or workboots. Be sure they are thick enough to resist being cut by metal edges of flashing materials. Also wear long pants & shirt that cover your arms.
  • Be aware of any electrical wires that may be on the roof. They might lead to an electric box or transformer, which can cause electrocution if you touch it while standing in water/rain with wet hands. Do not attempt to fix them!
  • Never go on the roof without a partner.


What about flushing the chimney?

Flushing is done differently than flashing. Once every year or two, you should clean out your fireplace before lighting it for the first time that winter. You can do this by removing all of the ashes and simply scraping down to bare brick with a wire brush (never use soap, detergent or any other chemical on the brick – it could be toxic). You want to remove all of the soot buildup from previous fires. Then, clean out your chimney flue using a stiff wire brush and vacuum cleaner with an appropriate attachment (be sure that this is a non-combustible surface first!).

How do I know if my chimney needs to be flashed?

You can tell if your chimney is flashing properly by looking up at the point where it meets the roof. If there are any gaps between that joint and the shingles, you need to do some repairs or call a professional for assistance. This means that water may potentially seep into your home! Additionally, if you've noticed that there is a lot of creosote buildup in your chimney, this could potentially indicate the need for flashing.

Does it matter when I do repairs?

It's best to make any repairs before winter (or summer if they are related to air conditioning). If you try and tackle these projects during colder weather, you risk getting sick from the fumes.

Why is flashing a chimney so important?

When water seeps into your home's exterior, it can cause serious damage to both the interior and exterior of your house! Cracks in brick or mortar could lead to other problems down the line if they aren't addressed immediately. The best way to safeguard against this is by preventing water from entering your chimney in the first place. Flashing ensures that none of it can seep through any cracks or gaps and into your home's structure.

See also
How to Fix Roof Leak Around Chimney (User’s Guide)

Is flashing a chimney hard?

It depends on what you mean! You may need some professional assistance, but overall, most homeowners can do the work themselves.

What tools will I need?

To flash your chimney, you'll need a wire brush (to remove any soot or creosote buildup), safety goggles and an appropriate chisel for scraping away mortar – it's important to make sure everything is non-combustible before working on it.

Is it possible to do this job by myself?

Yes! Flashing a chimney is something that many homeowners can and should try. However, you may need professional assistance if: * You aren't experienced or skilled at doing these types of home repairs; * Your chimney needs extensive work (for example, water damage); * You aren't comfortable working with these types of tools.

How long will the project take?

It should only take a few hours if you have experience and are familiar with this type of work. If you don't, it may be best to call in someone who does! It's important to set aside enough time so that your project isn't rushed.

What else should I know?

It's important to remember that you need to be very careful when working on your chimney! Always wear safety goggles and keep pets away from the area (if they're prone to getting into things). It can also help if there are multiple people available who can assist with these types of projects.

Is it possible to have a chimney fire?

It's not very common, but yes – you should still take precautions when using your fireplace for the first time after winter or if there has been a lot of rain/snow recently! It takes quite a bit for this to happen and usually only occurs in very old chimneys that have a lot of damage.

What do I need to know about fires?

It's important to keep your fireplace clean! Creosote buildup from wood smoke can ignite if there is too much in the flue or it isn't cleaned out regularly – you could end up with a very dangerous situation on your hands.

How long can I use my fireplace?

You should only use your fireplace for a few hours at most (longer if there is no creosote buildup). You'll also need to make sure that the damper is closed when you're done using it – otherwise, all of that smoke will come back into your home.

Does a fireplace need to be cleaned?

Yes! You should clean your chimney at least once per year, but every few months is better. If you notice any creosote buildup, it's important to clean it out as soon as possible – this could prevent the possibility of fire (or indicate that there are larger problems with your chimney if it's not cleaned out).

Can I clean the fireplace myself?

Yes! It may take some time, but you can definitely do this yourself. Just make sure that you're using all of the proper safety equipment (earplugs and fire-retardant gloves) before beginning. You'll also need a brush, a bucket and some chimney cleaner.

How do I know if my fireplace needs to be cleaned?

There are quite a few signs that indicate it's time for this type of project! Some include: * A sooty residue on the walls or floor; * White streaks running down your exterior brick – these can indicate that there is moisture in the chimney, which can lead to all sorts of problems.

What should I do if it needs cleaning?

If you see these types of signs, take your fireplace apart and remove any soot or creosote buildup before putting everything back together again! You'll need a good brush for this task and some chimney cleaner. You should also be careful to use a wire brush and not something too abrasive – this may damage the masonry of your fireplace.


In the end, it is always best to hire a professional chimney flasher for commercial buildings. For smaller structures such as houses and cottages, you should be able to get away with doing the work yourself if you follow these instructions carefully. If in doubt about anything related to flashing your chimneys, contact us at Chimney Repair and we’d be happy to help with any questions you might have.