Exterior Chimney Flue Towards Hail - Urban Chimney Inspection
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Although they may be difficult to see from street level, your chimney crown and wash plays an important role in protecting your chimney as well as your home. When the chimney crown is damaged, water can easily and quickly damage the masonry of the chimney, the flue of the chimney, and even the walls and ceilings inside your home.
Because the chimney crown is a somewhat flat horizontal surface, it is directly exposed to all sorts of weather, including sun, heat, hail, rain and snow. All this can cause even the most sturdy chimney crowns to crack, spall or crumble over time.
Learn how to size your chimney flue for a chimney pot. This chart displays guidelines based on typical dimensions of flue liners. Flue dimensions will vary depending upon manufacturer and age of flue liner. Be sure to accurately measure the flue liner before ordering a chimney pot to insure that the pot will fit properly.
Just like a wood built chimney chase, a masonry brick chimney can also benefit from having a stainless steel chase cover. A stainless steel chase cover will fit over the top of your chimney and prevents the elements, snow, rain, or hail from deteriorating your chimney.
There are two main types of prefabricated chimneys: air cooled chimneys and insulated chimneys (often referred to as solid-pack or non-air cooled). Each pipe requires a different type of chimney cap. If you look up at your chimney and you do not see a chimney rain cap on your flue, then a cap should be installed immediately to prevent costly repairs down the road.
Covering the top of your chimney is an important thing to do to prevent costly damage caused by the elements. At the top of every chimney are two parts, the chimney crown and the chimney flue. These two parts can often get confused. Understanding the differences between a chimney cap and a chimney cover will make purchasing what you need much easier.
This article describes the inspection of and common defects or hazards found at covers & terminations found at the top of chimneys and flues. We provide a checklist of chimney top or chimney rain cap defects for building owners, contractors, or inspectors.
A chimney rain cap is a rain cover on top of a chimney flue designed to keep out rain (which can damage the flue or appliances it vents) and intended to reduce downdrafts in the chimney in windy conditions.
Some chimney rain caps may be supported atop a masonry chimney in a position to shelter the chimney flue, and may not only cover the chimney flue opening but may also project out beyond the entire chimney top (red arrow, photo at left).
If you are concerned about the cap or crown seal around the chimney flue where it projects through the chimney top of a (usually) masonry chimney and don't care about the rain caps shown above, see this
A retrofit chimney rain cap is shown in our photo at above left. This rain cap is designed to fit over the top of a standard sized clay chimney flue tile and is held in place by four threaded bolts that press against the sides of the flue tile. Other chimney rain caps for clay tile flues mount by friction by insertion into the interior of the top of the flue tile.
Watch out: when installed over a flue used to vent a wood-fired burning appliance such as a wood stove or a wood-burning fireplace, creosote can condense on and quickly block the mesh of the spark arrestor, leading to a blocked flue or a chimney fire.
Watch out: we often find a temporarily capped-off fireplace flue or unused chimney flue that was left in that condition by a prior building owner. The new owner, attempting to use the chimney before its safety and condition have been determined, faces risk of being driven out of the home by smoke at a fireplace or worse, potentially fatal carbon monoxide poisoning if the flue is to be used by a heating appliance.
We've encountered cases of a homeowner returning to service a fireplace or chimney flue whose top was covered over completely as our photo depicts. The result is potentially fatal carbon monoxide poisoning or a fireplace that causes smoke damage in the building.
The chimney is no longer in use and preservationists wanted to protect the chimney interior and exterior from leaks and from further frost damage. At the chimney's left corner as well as in smaller areas below you can see evidence of severe frost related spalling of its brick surfaces. Also
The most common defect we observe at chimney rain caps is that there is none - the rain cap was never installed, or it has been lost or blown away. Below, photographs of two types of factory built metal chimneys illustrate the loss of the chimney's rain cap. At below right you can also notice water ponding around the chimney flue.
If we want proof that people don't spend a lot of time looking at their chimney, ask a home inspector or chimney sweep how often they find that the rain cap or spark arresting chimney cap has been completely lost from a chimney. At above right we see leak stains from water that has been running down the interior of this heating appliance chimney flue.
Water entering the chimney also risks corroded leaky flue vent connectors, leading to draft problems and carbon monoxide poisoning risks as well as costly or dangerous damage to the heating equipment itself.
Corrosion at the welds that connect the round chimney cap to the metal brackets that in turn connect the chimney cap to its mounting base has caused the welds to fail. Only one of 10 welds remained in place when I inspected this chimney; one good gust of wind was sufficient to blow the cap off of this flue, risking subsequent water damage to the chimney itself or to the oil fired heating boiler connected to this chimney.
Watch out for "faux brick" metal chimneys and flues such as the factory built metal chimney shown at left. This chimney, glanced-at quickly from ground level from the other side of the house, might be mistaken for a clay tile lined brick flue with a metal rain cap.
This is an all-metal factory-built chimney. And inspecting from the opposite side of the home one can observe rust stains that raise the concern for a rust-perforated, damaged chimney structure, wall, or flue.
This chimney is capped by having inserted a short length of metal flue with a riveted rain cap attached. The whole assembly slides down into the flue, blocking adequate flow of exhaust gases from the gas fired heater being vented.
At above right the round metal chimney rain cover seems to be so squashed-down as to nearly block the venting of that flue, perhaps explaining the stains and heat-damaged sealant around the flue (red and yellow arrows).
Greg, thank you for the interesting and helpful comments. I'll keep these in the article when it's updated.DanielHound"Sweating" to be more technical, is of course not sweating- the moisture or liquid you see on your chimney cap is condensed moisture from the flue gases being exhausted. Hot gas holds more liquid. It hits the cool chimney sides and cap as it rises up the flue. Those surfaces cool the gas, squeezing out moisture that condenses on the chimney and cap surfaces. It may be that your chimney is too short since you point out that you're using dry wood and building hot fires. Or there could be draft problems such as a chimney leak. I'd ask a chimney sweep, certified by the National Chimney Sweeps Guild (if you are in the U.S.) for a safety inspection and some advice.
Linda:If the rain cap design and opening dimensions restrict air flow then the system risks improper draft, improper or unsafe functioning. The un-used flue can be closed off at the chimney top to keep out pests and water; The in-use flue needs to have a UL-listed (presuming you're in the U.S., or CSA listed in Canada) rain cap properly sized for the flue that it protects. There is confusion about terms chimney crown, chimney cap, and rain cap; I hope we've sorted that out here.Don't pay before you know your system is properly protected and safe. Use the page bottom CONTACT link if you want to send me some sharp photos of the chimney top and rain cap.
Tony I'm not confident I can safely diagnose and recommend for this concern. Light soot from a woodstove at a chimney top may be ok but if soot blocks the cap, screen or flue there are indeed safety hazards. I agree that depending on the chimney height, enclosing the flue increases its temperature - but in wood burning I'm not sure what that does to soot at the cap.
Chimney crowns are the first part of your chimney to be exposed to the elements, and unchecked damage can result in increasingly expensive damage to the rest of your chimney. The crown of your chimney is a slab of concrete that protects your chimney's flue, brick, and mortar from rain, pest intrusion, and keeping your roof safe from flying sparks.The crown of your chimney can be damaged in a number of ways. Cracks can collect moisture, which can eat away at the cement, mortar, brick, or metal of your crown. It is therefore important to have your chimney crown repaired as soon as you detect a problem. Depending on the extent of the damage, your crown repair can cost anywhere from $200 to $1,000. More extensive damage can increase your repair costs.
Your chimney cap is the metal cap perched at the top of the flue that prevents water leaks that can damage the interior of your chimney. Caps can become damaged due to extended exposure to moisture, high winds, hail, ice, and other inclement weather conditions. Fortunately, chimney cap replacement is relatively inexpensive, ranging from $60 to $250, depending on the cap material and whether you have it installed or DIY. As with any chimney component, it is critical to complete your cap replacement as soon as possible, as moisture leakage into your chimney can cause more expensive problems over time.
Your chimney flue is the clay, ceramic, or metal passage between your fireplace and the outdoors. Its purpose is to direct heat and fumes out of your home without causing damage to the surrounding area. Over time, your flue can be damaged by leaking water due to exterior deterioration, structural damage from an impact or earthquake, or extended exposure to high temperatures and smoke from chimney use. If your flue is unlined, the cost to repair damage to flue tiles or resurface a cracked flue interior can range from $65 to $100 per foot. If you need to install or replace a chimney liner or flue liner, expect to pay between $2,500 and $7,000, depending on the liner material, insulation requirements, flue length, and diameter.Leak Repair CostWater leaks are the cause of most problems experienced by chimney owners. The cost of fixing a leak depends greatly on the location of the leak, the extent of the damage, and the type of material that must be repaired or replaced. A leaky chimney can be caused by cracks, rust or deterioration in the crown, cap, flue, liner, flashing, or masonry of your chimney. Your chimney sweep will often be able to detect a leak by noting the presence of creosote, or mineral buildup, on the brickwork of your chimney. To fix a leak, it is important not only to repair the source but to trace and repair any damage that has occurred as soon as possible.Remember that every part of your chimney is constructed to direct harmful smoke, gases, and sparks out of your home. A damaged flue may not direct heat or smoke correctly, increasing the potential for smoke and heat to escape into your home. Similarly, a damaged damper, firebox, or smoke chamber can reduce the efficiency of your fireplace and allow smoke and fumes to blow back down the chimney and into your home. Cracked or deteriorated exterior components that have been eroded by moisture can allow excess heat and sparks to escape, significantly increasing the risk of fire. Left unchecked, a water leak can cause spalling and structural damage to your chimney that makes it very expensive to repair or replace, so time is of the essence. 781b155fdc