Category Archives: Chimney Repair

Chimney repairs can cost a lot of money, so you want to do your research and get done what needs to be done. Chimneys in ill-repair can cause a host of issues including house smoke, water leaks, increasing fire risk, carbon monoxide leaks, and even toppling over. So do your research to make sure you know what needs done and ensure you get the right repairs done right.

We hope the articles below can help you out with that. And if you happen to be in the Washington DC area and suspect you may need chimney work, please call High’s Chimney service.

Is Chimney Repair Covered by Homeowners Insurance?

Is Chimney Repair Covered by Homeowner’s Insurance?

Short Answer: It Depends. Here are some answers to questions we regularly encounter, and hopefully, a lot of insight into the whole subject of “insurance coverage and chimney repair.” Continue reading

Your Source for Fireplace and Chimney Information

The following library of information is broken up in a way that will educate you on your chimney so you know how your chimney should be properly cleaned, maintained, and/or repaired. If you can’t find what you’re looking for, leave us a note in the comments and we will try to find you an answer!

The Basics

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DIY Masonry Repair

DIY Masonry Chimney Repair: A Warning

DYI Masonry Repointing Gone BadThe do-it-yourself movement has taken the world by storm. With the ability to bring up video walkthroughs for most tasks, hiring a specialist is often viewed as a last resort. The spread of information over the internet is an amazing and life changing phenomenon. Suddenly, replacing the belt in your vacuum is no big deal. Changing fuses in your car is a snap. Is your garbage disposal clogged? You can find countless walk-throughs to help clear that obstruction.

This prevalence of do-it-yourself walk-throughs, however, has left people attempting do-it-yourself projects that are sometimes best left to the professionals. While saving money in the short term is a great thing, it’s important to remember the long term too. Saving money right now hardly counts if it ends up costing you twice as much later.

Masonry is especially susceptible to the DIY problem. Countless articles exist online about repointing brickwork, filling splits or cracks, or even replacing spalled brick. As chimneys are often in need of some work, many look to these articles when contemplating how to fix their masonry chimneys. While these might seem like helpful resources, in the long run they can cost you more in time and money than your local masonry professional.

Most DIY masonry repair articles mention mortar only in passing. While they mention its use between layers of brick, they rarely emphasize that mortar isn’t just a slapdash mixture of sand and water. This omission can be costly and belies their disinterest in supplying a genuinely useful article as any trained mason knows that improperly mixed mortar can cause massive masonry damage.

Mortar exists as a cushion between bricks. As bricks swell and contract from temperature changes, a proper mortar absorbs these changes. Gradually, that causes the mortar to crumble. This mortar can then be replaced with relative ease by a professional, providing another 25 or more years of low-maintenance service.

If the mortar is mixed so that it is stronger than the surrounding brick, temperature changes actually cause the mortar to squeeze, and thus damage, the brick. This causes the bricks to spall. Spalled bricks cannot be repaired, and must be replaced before further damage accrues. If incorrect mortar mixture is the cause of the spalling, the mortar must also be replaced to prevent further damage.

Mortar that is too soft, on the other hand, quickly deteriorates and requires premature replacement or repair. If it deteriorates faster than surrounding mortar, this can create instability in the masonry, and if left unchecked can even cause collapse.

When so many masonry professionals offer free initial consultations, taking advice from strangers over the internet seems a poor choice. For those in Northern Virginia, Washington D.C. and Maryland, High’s Chimney offers free masonry estimates where we discuss problems with your masonry chimney and how we would fix them. Not just handy-men, our highly trained masons have years of experience, ensuring that your masonry chimney is safe.

Masonry Chimney Damage & Repair

Damaged Masonry ChimneyRegular maintenance on your masonry chimney will keep it looking great for years. In reality, though, regular maintenance falls through the cracks while you juggle work, life and family. Sometimes, even the most proactive homeowners will be surprised by damage left by previous owners. So while in a perfect world, repointing would be the only masonry service the average masonry chimney would need, in reality you might find unfamiliar problems with your masonry.

Masonry Chimney Damage

Chimney with Spalled BrickSpalled Bricks

Broken (or spalled) bricks are one of the most noticeable types of damage. This is most commonly seen when the front of the brick has either broken or fallen from the masonry.

We’ve mentioned before that the largest cause of damage to brick and masonry is freeze and thaw cycles. Bricks are built to withstand water by finishing them with a hard non-porous outer shell. Spalled bricks break this shell and expose the porous interior of the brick, allowing water damage to destroy your masonry at an accelerated rate.

Spalled bricks are primarily caused when mortar with an incorrect compression rate is used. Mortar is made to absorb the expansion of brick during freeze and thaw cycles. If the mortar is stronger than the brick, however, this role reverses. As brick isn’t meant to be squeezed by expanding materials, it can quickly deteriorate.

The Wrong Bricks

All bricks are not created equal. Brick makers understand that interior bricks don’t need to weather the same abuse as exterior bricks, and thus make different types of bricks. When buying bricks, the difference between these is obvious. It becomes a problem, however, when bricks are salvaged. Inexperienced masons and do-it-yourselfers have a difficult time determining which bricks were meant for interior and exterior use.

Some brick makers even make different bricks for different climates. The Deep South is free from freeze and thaw cycles, so some brick makers decided to change the type of brick they shipped there. Since these bricks didn’t need to withstand the same type of abuse as bricks used in the North, they added sawdust to the brick mix. When the bricks were fired, the sawdust burnt away, creating a lighter, more porous brick. This saved on transportation and made it easier for masons. While this caused little problems for the South, unfortunately these bricks were soon being sold further north, where they easily crumble under the extreme temperatures.

Damage from sandblasters and pressure sprayers

An unexpected source of damage is sandblasters and high pressure sprayers. While these might make cleaning a hands free experience, they do so at the expense of your masonry. As mentioned earlier, brick is made such that the edges are hardened to prevent absorption of water. Sandblasting and even high pressure sprayers can reduce this hardened edge and allow water into your bricks, drastically reducing their lifespan.

Masonry Chimney Repair

Unfortunately, there’s no easy way to fix spalled bricks. Removal of the spalled bricks and replacement with strong new bricks is necessary. If the spalling is caused by poorly calculated mortar, repointing with correct mortar may help to prevent the problem from spreading.

If you suspect your masonry might be made with bricks that can’t stand up to your weather, or if you have sandblasted or pressure sprayed your masonry, we can apply a waterproof sealant to help the longevity of the bricks.

And of course, if you notice any spalled bricks, cracks, crumbling mortar, or signs of deterioration on your masonry chimney, it’s time to contact a masonry expert right away. Ignoring masonry problems is dangerous and costly.

If you have questions about masonry repair in Northern Virginia, Washington D.C. or Maryland, we at High’s Chimney would be happy to answer any of your questions or take a look at your masonry and give you an estimate for repairs free of charge.

Time to Repoint this Masonry Chimney

How to Repoint a Chimney

Why Chimney Repointing is Essential

Repointing is a necessary component of chimney masonry maintenance. Well done mortar joints can last for 25 years before repairs are needed, but the brick that surrounds them can easily last 100+ years. Weather plays a large factor in determining how long your mortar joints will last.

Time to Repoint this Masonry Chimney

Time to Repoint this Chimney

Washington DC is known for its unique blend of weather. Sandwiched in by the Blue Ridge Mountains to the West and the Chesapeake Bay/Altantic Ocean to the east, our weather is unpredictable. When the weather begins its steady descent into winter, we’re especially susceptible to changes in temperatures, rain turning into sleet into snow, followed by a crisp and sunny winter day. This weather might mess with your head, but it slowly destroys your masonry. Moisture is absorbed into brick and mortar, and with the temperature fluctuations the water expands and contracts. If brick and mortar were equally strong, this thermal expansion would cause irreparable damage to brick and mortar.

For this reason, the compression strength of mortar is less than the brick. As temperatures fluctuate, the expanding brick overpowers the expanding mortar. Over years of thermal expansion cycles, this will cause enough damage to the mortar that it will need to be repaired. If mortar wasn’t calculated to be softer than bricks, regular reconstruction of your masonry would be necessary.

The Chimney Repointing Process

Repointing a masonry chimney requires a skilled professional. Repointing is far more than just slapping some mortar into cracks. The process requires different skills than traditional masonry, and even masons with years of experience might not have significant experience repointing brick.

Before Repointing Assessment: The biggest challenge of repointing is determining the extent of the mortar damage and removing damaged joints without causing new damage. Generally, an expert starts with a visual inspection where erosion deeper than 6mm, crumbling mortar, and cracks between brick and mortar or within the mortar are noted. After the visual inspection, specialized tools such as metal scrapes or special low pressure water sprayers might be used to determine the extent of the damage. Once the determination has been made, the deteriorated mortar joints must be removed.

Removing mortar joints: It’s important that the joint be removed to an appropriate depth without causing extra mortar or brick damage. Once the joints are removed, the new mortar must be mixed. This mortar should be as similar in composition to the existing mortar as possible, lest thermal expansion cause the mortar to react differently to the pressure of expanding brick. Ignoring this step could lead to premature mortar deterioration. Using mortar with excessive compression strength can cause permanent brick damage, such as cracking and splitting.

Applying mortar: The correct mortar is then placed between the brick by layering, compacting and tooling. This helps adhere the old mortar to the new, and ensures a snug fit between brick and mortar.

Professional masons experienced in repointing also take care to match the shade of the new mortar to that of the old. This is purely aesthetic, and keeps the chimney repointing from looking sloppy. A skilled mason will do this with minimal mess, and will ensure the brickwork is clean before finishing the job.

Applying mortar during repointing chimneyApplying Sealant: Finally, a waterproof sealant is applied to the fresh repointing. This will help prevent water from permeating your chimney, and thus will help extend the life of your mortar joints.

Just RepointedGet the Chimney Checked

While all masonry will need repointing at some point, chimneys are particularly susceptible to water damage. Their location subjects them to constant temperature changes while making them difficult to monitor for signs of damage. Before fall slides into winter, have your chimney inspected for mortar damage. Timely chimney repair can save you money, and our free masonry inspection will give you peace of mind that your chimney will be sturdy and safe all season.

Masonry Chimney Repair & Relining

Masonry Chimney Repair & Relining

The Washington DC area has a rich history of architectural styles. From brick farmhouses in Fairfax to Victorian row houses in Georgetown, Washington DC has preserved much of its architectural history. These homes have weathered decades (or centuries) of use, remodels and updates while still possessing an undeniable charm. The sturdy construction of these historical buildings plays a large part in their continued existence, but constant monitoring and maintenance is what keeps these charming homes instead of quaint historical exhibits.

Routine inspections and preventative maintenance can help keep houses old and new running smoothly. For many components of your home this can be a simple process. For example, wear around your windows and persnickety plumbing are easy to spot. For other parts of your home, such as your chimney, a little effort is required.

Chimney Masonry Maintenance

Most responsible home owners ensure they have a proper flue with optimal draft and that the major components of the fireplace are functioning properly. This diligence causes the illusion of security; so long as no major problems occur, their chimney must be healthy. In reality, without a watchful eye, water damage can compromise the integrity and safety of your chimney long before you notice the problem. While the rest of your roof is protected from the elements, your chimney is exposed to the worst of Mother Nature.

While the brick itself generally fares well against such odds, without water proofing the mortar is heavily susceptible to water damage. Specifically, mortar absorbs moisture. As the temperature changes, freezing and thawing cycles cause this water to expand and contract, which will cause cracking. This damage is often subtle, and by the time you notice crumbling mortar you will likely need masonry chimney repair. As it progresses the mortar will erode out from between the bricks, causing their weight to shift. This causes additional stress on the masonry, and exacerbates any existing cracks or stress points. Without proper care, mortar erosion will cause an unsafe and unsightly chimney that will need major masonry chimney repair. At this point a chimney professional will need to repoint the brick, and apply a waterproof sealant to prevent future water damage.

Masonry Chimney Relining

Chimneys suffering from masonry damage can let an excessive amount of water into your chimney’s interior. If you actively use your chimney as a vent, this can affect your flue, fireplace, and any appliances that vent into the chimney. For example, rain running down a used flue will mix with creosote and other deposits, causing a corrosive solution that can deteriorate your flue. This corrosive solution can drip down onto fireplace hardware, such as dampers, and rust them. Even if your chimney is perfectly clean, rain water will settle into any joints or cracks in your flue, where temperature changes will cause it to expand or contract, causing damage. This will cause a premature need for chimney relining.

Even if you don’t use your chimney as a vent, masonry chimney repair is important. Crumbling mortar allows moisture to permeate to the interior of a chimney. Inside the chimney, it will run down the joints in the masonry, leaking into cracks. This compromises the structural integrity of your chimney, which is never safe. Relining and repointing the interior of a masonry chimney is an expensive and time consuming process. To be able to work in such tight spaces, it’s often necessary to punch holes in the chimney to be able to ensure the proper work has been done.

If you have questions about masonry chimney repair or suspect you might need masonry chimney relining, contact us at High’s Chimney. We want your home to be a healthy, safe place to live. We offer free consultations on masonry repair, and our real time online scheduling service makes it easy for you to pick a time that works with your schedule. Being proactive about problems as they arise, such as masonry chimney repair and relining, is the best way to ensure your home remains a safe and stylish place for you and your loved ones to enjoy for years to come.

How Many Things Can You Put On One Chimney? Or Multiple Appliance Venting

Let’s start with a few definitions.

chimney flue ventingAppliances include fireplaces, woodstoves, furnaces, boilers, pellet stoves, hot water heaters, etc. They’re all individual appliances.

A chimney is a structure that has one or more flues in it.

A flue is simply the chimney passageway that vents the fumes from whatever is attached to it. (A flue is not the same as a damper either; a damper is something that can block the flue.)is simply the chimney passageway that vents the fumes from whatever is attached to it. (A flue is not the same as a damper either; a damper is something that can block the flue.)

How many appliances can you have per chimney?

And even though the question always comes across as “how many on one chimney?” let’s make sure to discuss “how many on one flue?” The answer to the question is: “It Depends”.

The rules are found in various NFPA standards and in the IRC (International Residential Code.) This article is general in nature but for those who want to drill down into the details, most of the information can be found in IRC chapters 10, 13, 18 and 24.

Solid fuel burning appliances.

Solid fuel includes coal or corn or cherry pits, but for most of us that means cord wood or pellets. The rule here is easy and clear.

IRC M1801.12 (PDF Here) Multiple solid fuel prohibited. A solid-fuel-burning appliance or fireplace shall not connect to a chimney passageway venting another appliance.

In other words, only one appliance per flue, period. It goes without saying, I hope, that gas or oil appliances cannot be vented into a flue which also vents a solid fuel appliance. EVERY SOLID FUEL APPLANCE GETS ITS OWN VENT!

How about hooking up a woodstove into an existing masonry fireplace flue?

That’s OK as long as:

  • The fireplace has been blocked off. Remember, only one appliance per flue!
  • The liner for the woodstove has to be properly sized, which generally means the same size as the collar-size coming from the appliance.
  • Make sure the chimney is clear of combustible materials before inserting the smaller liner.

Gas and Oil Appliance Venting

Gas fireplaces are factory-built systems. The manufacturer’s listing and instructions will preclude attaching any other appliances to it.

Multiple gas or oil furnaces or boilers, as well as hot water heaters, can be vented into one flue. There are a few rules to mention:

  • The rules apply to listed appliances. While I have never seen an unlisted gas or oil furnace in my life, if you have one, you are referred back to the rules for solid fuel burning appliances- one per flue.
  • If venting two or more appliances on the same flue, you have to know the flue can handle it, as determined but the BTU input and other factors.
  • Both or all appliances have to be on the same floor. So, no furnaces in the basement or room heaters on the second level of your home.
  • The connectors for the appliances have to be offset. They can’t come into the flue at the same height, and especially never directly across from each other.
  • The smaller of the two connectors go into the flue above the larger one (usually meaning the hot water heater).
  • As a general rule, don’t mix “natural draft” appliances and “fan assisted” appliances on the same flue. This rule is more complicated than this, but if this is your case, be sure you refer to the manufacturer’s instructions. Call an HVAC company and make them show you to your satisfaction it’s right. Don’t take anyone’s word for it, see it in writing.

The NFPA 54 (Gas) and the NFPA 31 (Oil) show diagrams in great detail, and cover sizing the connectors as well (connectors are the smoke pipes that carry the fumes from the appliance to the chimney flue.)

Read another helpful article by the American Society of Home Inspectors.

Five Reasons for Chimney Leaks and What to Do About Them

Causes of leaking chimneys can usually be narrowed down to five reasons. If your problem isn’t solved from addressing the items on this list, your leak probably isn’t from the chimney!

common masonry chimney leak fixes

#1 The Simplest Cause of Chimney Leaking: Rain Going Straight In from the Top

Capless Chimney

Capless Chimney (source: hersheychimneycleaning.com)

It’s not hard to picture that. Chimneys without covers get a lot of rain falling straight down into them. A chimney cover makes sense to most people. Not only does it keep the rain out, but keeps birds, animals and debris out. The greatest value of the chimney cover is really keeping these out because when chimneys get blocked at the bottom, people get sick (or even die) from CO poisoning. While it’s true that sometimes an uncovered flue is the source of water problems, most often this reason for a leak is only when the liner is metal.

How to fix it

Get a chimney cover and have a professional make sure it’s not this simple.

#2 Many Chimney Leaks are from Cracks in the Chimney Crown

cracked chimney crown

Cracked Chimney Crown

The chimney crown is the cement part on top of the chimney. The bricks go up around the tile flue liners, but at the top you need something to stop the rain and snow from just falling in around the tiles. You can see that the very purpose of the chimney crown is to keep rain out. Cracks in the chimney crown can occur from shifting of the structure or from shrinkage dating back to the first day the crown was put on. When your crown has cracks, the water goes right through those cracks.

How to fix it

How to fix a cracked crown depends upon how bad the damage is. Most crowns have small cracks. Even small ones need to be fixed because all big cracks started out as small ones. Water freezes and thaws in the cracks all winter long, year after year, forcing small cracks to eventually become big cracks. There are excellent crown coating materials such as Chimney Saver Crown Coat which cover the masonry and prevent small cracks from becoming a real problem.

Once chimney crown damage is significant, though, the only fix it is to remove and relay the masonry. You can’t put a band aid on a gushing wound and you can’t coat a structurally ruined chimney crown and expect it to work. Best to coat your crown now with Crown Coat and avoid the big hassle and expense later.


chimney inspectionLeaky Chimney? We can fix that! If you believe that your chimney is causing damage to your home please give us a call or schedule an appointment online. We’ll be happy to help you.


#3 Chimneys Leaking From the Inside Out from Condensation

damage from chimney condensation

Damage from Chimney Condensation

I remember a lady whose wallpaper peeled where the chimney ran through the house. She knew it was the chimney because this is the only place with wallpaper peeling. She had tried everything- a chimney cover, flashing, even rebuilt the entire top of the chimney. By the time I met her she’d spent thousands of dollars but nothing fixed it.

This was an older house with an unlined brick chimney. In 1900 when it was built that chimney carried wood or coal smoke I’m sure. Someplace along the way a gas furnace was installed, but the chimney was not lined with a properly sized liner.

How to fix it

Gas fumes are very low temperature and have a lot of moisture in them. These fumes were condensing on the inside of this too-large, too-cold old chimney, literally soaking the bricks and keeping them moist all the time. All it took was a chimney liner and we solved the problem.

#4 Chimney Flashing Causes Leaks

bad chimney flashing

Chimney Flashing Leaks

TThe flashing is what keeps water from going into the place where the brick structure comes through the roof (or otherwise comes close to the roof.) There’s a fairly large gap between the bricks and the roof and water will pour through that hole if it’s not sealed up. Flashing is often aluminum that goes in between a couple bricks and bends to go on top of the shingles. Some sort of water proof “stuff” seals those spots. Though it’s far from the best choice, the “stuff” is often tar. In any event, flashing doesn’t last forever and the tar lasts even less time.

How to fix it

There are better materials for sealing the flashing now. If you get a chimney sweep to fix your flashing, tell him you want Flash Seal by Saver Systems. (As you can see, I like Saver Systems products; but they just work well, so you can’t go wrong!) It seals better and lasts longer.

#5 Chimney Leaks Caused by Leaking Bricks

leaky bricks

Leaky Bricks; Source: doityourself.com

Bricks and mortar both pass water, and often lots of it. The problem here is the same as with the crown- the freezing and thawing all winter long with the resulting damage which causes leaks in the house.

You have probably heard of waterproofing a chimney, but you have to be careful about what waterproofing material to use. When water is absorbed into a brick or a mortar joint in the summer time, the water probably dries out after a while. The exceptions might be for a surface in the shade or on the side of the house where the sun never shines; those walls just stay wet. That water does try to escape by “falling” i.e. the water weight (or head pressure) carries it toward the ground where it forces its way out of the bricks either inside or outside of the house.

If you apply a waterproofing material that physically blocks the pores of the brick or mortar, the water is trapped inside the brick. Some bricks actually get soggy, though it’s more likely that the water will just seep to the inside of the house. To the point, using silicone based water sealants may trap water and cause more damage than you started with. Use polysiloxane type waterproofing agents, such as Chimney Saver by Saver Systems.

How to fix it

To find out if your chimney leaks through the masonry surface, have your sweep do a Masonry Absorption Test (MAT) This is a simple test where a special test tube is attached to the side of the chimney and you record the time it takes for water to be absorbed into the wall. This tells you if you should waterproof the chimney.

Bonus: #6 Chimney Leaks That Aren’t Chimney Leaks

non chimney leak

source: www.orionrestoration.com

Sometimes, a leak starts in a different place but finds its way to the chimney, and then visibly enters the inside of a room at the point of the chimney.

For example, your roof might have a leak through the attic vent or roof shingle at the top.  Water could get into the attic or above your ceiling and either drip to the floor or roll along the stringer (the long piece of wood that spaces out the roof trusses and runs the length of your house). If the stringer is un-level, water can travel a ways – and even wind up at the chimney. It has happened, and usually isn’t discovered until people have spent a terrible sum fixing everything else.

Another event that could happen (although I have never heard of it actually happening) is that you could get so much moisture in your attic that it could condense and roll down the stringer onto your chimney.  This could happen if there were some reason your attic was getting a lot of humidity in it – for example, if your dryer vented into the attic instead of out of a vent perhaps, or if your gas furnace were vented by B Vent but just dumped into the attic (which would be a severe carbon monoxide risk, incidentally).

–Need help with your chimney leak repair in Maryland, DC, or North Virginia? Call High’s!

Chimney Airflow Problems

Understanding chimney draft problems is not necessary for most people. Usually, if you notice smoke not rising from your chimney, you can call on a professional to fix the issues.

chimney draft problems

Draft problems can cause you problems!

This information is for those who really like to understand; it may be too much information for many people. I’ll do my best to keep it as interesting as it can be. If you’re a do-it-yourselfer or the owner of an old home, you’ll probably get a lot of out of it.

Understanding Chimney Draft Issues

To understand the problems, you need to understand what draft is. Draft is what we name the effect of how the air flows up the chimney. It’s measured in “inches of water column.” Draft then is the combination of volume, speed, and pressure of the flue gasses. And temperature of the gasses comes into play here as well.
For matters of this discussion, chimney draft is usually thought of as the speed at which the vented gasses travel up the stack, or pressure of the gasses. This can also be referred to as the stack effect. A common question might be “how strong is the stack effect?” Good draft conditions mean that the vented gasses are traveling up the chimney quickly rather than slowly or not at all.

How Does Chimney Draft Work?

The reason smoke (or other flue gas) goes up the chimney at all is because of the vacuum in the chimney. The question you should ask now is “a vacuum relative to what?” The general answer is that it’s relative to the air in the house. Don’t read too much into that because it gets tricky (for example, how does replacement air get into the house?- because the house environment is a relative vacuum to the outside. Yet the inside of the house is not a vacuum compared to the chimney.) Let’s keep this simple and just talk about the chimney. The pressure in the chimney is typically less than that inside the house. Thus, the draft effect is caused by air inside the chimney being pushed up the chimney by the house air.

And why is there a difference in pressure in and out of the house, or in and out of the chimney? There can be a few reasons, but the biggest and most important reason is the temperature difference from one place to another. Remember that when air is heated it expands? The same amount of air occupies a larger space, or you could say the same amount of space has less air (fewer molecules of air.)

The air outside the house in the winter is colder and heavier than the warmer air in the house. It pushes its way into the house (or is it pulled, depending on how confused you want to be.) The air in the chimney just came from a fire so it’s really hot and expanded and being pushed up the chimney to the cooler air outside where warm air rises, right? That’s buoyancy. Problems occur when these processes don’t happen correctly.

Diagnosing Chimney Draft Problems

Draft is measured with a pressure meter that has a probe which goes into the smokepipe. The meter should register a negative number, and generally speaking for residential heating appliances that number would range between -0.02 to -0.04. Zero or a positive number means the gasses are not going up the chimney. And too large a negative number can have its own set of consequences; but that isn’t usually the problem. Mostly “a draft problem” means the gases are not going up the flue, this is merely a minor chimney repair.

Causes of Draft Problems

Chimney Airflow Issues

Chimney Airflow Issues

Now there are other reasons for draft problems. One is called Dynamic Wind Loading. or “DWL.” DWL is caused when the wind blows on one side of the house and causes a positive pressure, and creates a corresponding negative pressure on the other side of the house.

If the windward side of the house is tight and the lee side (negative pressure side) isn’t, the vacuum resulting from the wind can suck air out of the house. And the most likely source of that air is the chimney; it’ll pull down on the chimney, smoke and all and keep it from exiting your house! Or if a gas furnace is being vented you won’t see smoke but you still get the carbon monoxide.

The way to deal with that is to tighten up the lee side of the house and then put in an outside-air source. There are kits for that or you can just crack a window on the windward side of the house.

Chimney Draft Issues Caused by Fans

Big Kitchen Vent Hood

If your ears pop when you turn on your kitchen fan, you’ll probably have chimney draft issues.

The other large reason for bad draft is when chimneys have to overcome fans in the house. Kitchen fans, bathroom fans, radon fans. It doesn’t take much of a fan to overcome a natural draft appliance (such as a fireplace or woodstove) Again, the best answer is to allow “make up air” into the house.

The problem with that of course is that you don’t want a draft across the floor and you hate to purposefully introduce freezing cold air into the very house you’re trying to heat. It’s a Catch 22, but I can tell you CO poisoning is a bad thing, and smoke in the house is a bad thing. You just may have to make some choices.

Air Flowing Down Your Chimney

Finally, sometimes air actually blows down the chimney, but less frequently than you’d guess- it’s usually something else. But maybe your chimney is short and next to a larger part of the house or a bigger building. The same problem occurs if your house is located at the base of a mountain. If you have this problem, a Vacustack is a good solution if you can’t raise the chimney to the proper height.

This Old Chimney Part 2

Problems With Older Chimneys Continued

In this two part series, we’re discussing typical problems that owners of old homes have with their chimneys. This Old Chimney Part 1 begins the conversation that we’re continuing this week.

Chimney Smoking Issues

Fix a Fireplace Smoking Problem

Smoke Stains on a Fireplace

If you see smoke on the face of the fireplace above the lintel (The thick metal bar that holds the bricks across top of the opening,) it is a sign that the chimney is smoking. This is fairly common issue with old chimneys. There are a few reasons why chimney airflow problems occur.

Older houses are usually not very air tight; in fact they’re more likely to be drafty. But maybe the house has new windows and doors, the walls are tight etc. so maybe the house can’t breathe. This can cause a change in air pressure that hurts the drafting process that causes smoke and gasses to rise up the chimney. It’s unlikely that an old house can be sealed up so effectively, but it is a possibility.

More likely is that the flue is either blocked or was never properly sized. Proper sizing means that there is a relationship between the size of the flue and the opening of the fireplace. Think of this in a ridiculous extreme: if you had a flue the size of a soda straw you would not expect a fireplace to draft properly. There are ratios that work or don’t work. That ratio can be changed with a smoke guard. These are commonly available from hearth shops and chimney sweeps. Glass doors usually will help a chimney smoking problem as well.

Gaps in the Chimney Bricks: Fixing Fireplace Air Leaks

Fireplace Air Leaks

Gaps in the Bricks Causing Air Leaks

There’s often a space between the bricks on the front of the fireplace (the wall, or the “face bricks”) and the structure of the fireplace itself. Sometimes that gap is on the floor by the hearth (in front of the wood burning fireplace too.) Not good. These gaps are probably caused by the old house settling over time.

You should inspect the fireplace carefully with a bright light to see if any wood is visible. If so, stop all action and call in a professional CSIA Certified Chimney Sweep. Wood in this area can cause fires quite easily and is a real safety hazard. If you don’t see anything, then get a chimney sweep to pack the gap with ceramic wool and refractory cement. Packing the hole yourself with typical cement won’t work because of the extreme temperatures in the fireplace.

Common Hearth Issues

Did you ever wonder how the hearth “stays up” that is to say: what supports all that weight? What’s under those bricks and that heavy firebox? The answer could surprise you- sometimes very little! Or sometimes, commonly found in old houses, there’s wood. Not good.

Go to the basement and look up to see what’s supporting the hearth. If you have metal I beams then great (I’d be surprised if you do.) Perhaps it’s supported on a masonry foundation, and that’s good. Or if you see cement that’s probably fine too, while it’s not clear what’s holding the cement in the air (though something obviously is) at least it’s not combustible.

But if your hearth is supported by sitting on a piece of plywood, you need to change that. More than one house has burned down because of that sort of thing.

Improving the Smoke Chamber of your Old Fireplace

Fireplace Smoke Chamber Parging

Parging the Smoke Chamber of The Fireplace

Above the damper area is the smoke chamber. This is the area where the wide fireplace funnels up to the smaller flue. The bricks are stepped in, or corbelled. That’s a rough surface, and it makes for a) less draft, b) more heat transfer though the wall c) a dirtier chimney. And modern codes say they should be parged. Parging is the practice of spreading some sort of cement over the corbelling to smooth out those square steps. This is not something you can do yourself. Somebody has to open the back of the smoke chamber (take bricks out) and reach through the hole to parge. Alternatively there are materials that can be sprayed (sort of like Gunnite, only it’s a different material.)

Call a chimney sweep and ask him if he’s able to spray or parge the inside of the smoke chamber. You may need to make a few calls to find somebody, because the work isn’t easy and it’s not fun. But it’s worth doing- the smoke chamber is usually the weakest part of the system next to the chimney itself.

If you’re lucky, that area is already parged and the parging is holding up well.

Common Old Chimney Problems

Well, that wraps up our conversation on old chimney problems. Have questions? Old home stories? Let us know in the comments section!