I need a chimney cap for a brick chimney with 2 flues. The outside dimensions are 17.25 x 41.75 inches and the flues are flush with the top of chimney. Can you recommend which cap would work best?
I normally suggest going right to the edge of the chimney crown to make sure you have maximum coverage in the event of heavy/slanted rain. With your flue being flush, I'd say a 41" x 17" cap with an 8" height would be ideal.
There is no standard chimney cap. With masonry fireplaces, the construction is very much subject to builder discretion and the flue measurements will subsequently vary widely. With manufactured fireplaces, the chimney and chimney cap will be very specific to the fireplace.
How far above the top of the flu do these chimney cap covers need to be?
When selecting a chimney cap, you will need to ensure the mesh height or lid will be at least 5" taller than the highest flue tile that extends from your crown. Typically, the terracotta flue should extend 2" above the crown, splay or wash, however, the flue tile can sometimes be level with this surface or extend much higher than 2". We have caps on our site that can accommodate this issue and we also have a custom fabrication department that can make a cap to your needs, with the proper information provided.
Is there a minimum distance from the top of the flu to the underside of the top of the cap?
The minimum required gap between the top of a clay flue tile and the underside of the cap lid is five inches. Keep in mind that this is a minimum and an inch or two of extra space will help to improve draft further, especially on shorter chimneys.
Do they make a chimney cap with mesh small enough to keep the bees out?
For instances when small insects are a nuisance, I recommend wrapping the factory chimney mesh with a smaller gauge stainless steel wire mesh. So as not to impede draft, I do not recommend going smaller than 1/8 of an inch.
Submitted by:Collin C. - NFI Master Hearth Professional on February 25, 2013
A more expensive option than tile mount caps, surface mount models are an appealing option due to their durability and protection level. Designed with a removable top lid, a perimeter screen, and a set of base plates, they are made to attach directly to the chimney wash (the masonry covering on the top of the chimney around the flue). The base plates have a series of perforations drilled for their entire length, allowing you to line up the plates, mark holes to drill into the chimney wash, and then attach the base plates with masonry anchor screws. The base plates on many caps are hinged, allowing for sloped chimney surfaces to be accommodated.
This cap style offers flexibility on size, since you can choose to order a cap just big enough to cover the chimney tile, or select a larger one that will cover the entire chimney top. More coverage will help the chimney wash to last longer and will offer greater protection against wind-driven rain or snow, but it is more expensive that the narrow coverage models.
Band Around Caps
Although not as common as the other styles, this cap is designed to band around the outer perimeter of the entire chimney. It differs from tile mount/outside mount caps by using much larger bands that lock together and adjust as needed. It can only be used for outside perimeter mounting.
Cap Styles for Prefabricated Metal Chimneys
Made specifically for prefabricated chimney pipes, this style of cap has a spring wound base (a metal coil that narrows when squeezed and then springs back into shape). When installing the cap, simple squeeze the spring to compress it and push it down the chimney pipe. When released, the metal springs out and wedges itself into the chimney pipe, holding the cap in place. We recommend you also run self tapping screws through the outer wall of the pipe and into the cap after installation.
These caps come in two styles: solid pack and air insulated. Solid pack push-in caps are designed for use with solid insulated chimneys like DuraTech or SuperPro and do not allow for air to enter the chimney. Air insulated push-in caps are designed to work with most chimney systems associated with factory-built open fireplaces. The cap has an internal baffle that allows air to enter between the inner and outer walls of the chimney.
Specialty Cap Styles
Liner caps are similar to a push-in chimney caps, but instead feature an outer clamp that is designed to be tightened to a chimney liner installed into a masonry chimney. This type of cap is usually only available in stainless steel.
This style of cap is designed to extend the length of a masonry chimney that is too short to draw properly. Insufficient height can cause issues with proper chimney draw, so a low cost solution is to use a flue stretcher to lengthen it. The cap is basically a tall tile mount cap, but instead of a mesh screen for the entire height, solid material is used for the first 1 or 2 feet before opening to a mesh screen. These caps are not recommended for high wind areas, as their large size makes them susceptible to blowing off or buckling under a high wind.
As the name implies, this cap is designed to help alleviate wind related issues. Usually attached with specialized adapters that allow for installation to a chimney pipe or masonry flue, the cap consists of a series of overlapping baffles that prevent wind from directly entering the chimney flue. It also usually has screen mesh installed between the baffles to allow it to function as a debris guard like any other cap.
Looking for something to fit a unique configuration? Contact us to get a special quote on a custom chimney cap in whatever size you want!
We can order custom caps through Copperfield Chimney (one of our suppliers) and they produce them under the Gelco brand. Although a custom chimney cap or chimney cover can be more expensive, the size options are far longer, wider, and taller than anything else on our site and are perfect for installations that need a non-standard size. The quote turnaround is very fast and production is usually 5-7 days for most orders.
Speaking of brands and suppliers, here's a roundup of some of the top brands for chimney caps:
HomeSaver - A well known manufacturer of chimney re-lining components, chimney caps, and insulation products, this company offers high quality stainless and galvanized caps in many styles.
Gelco - A sister company of HomeSaver, Gelco offers a broader range of material options, styles, and most importantly, full customization of chimney caps through authorized retailers like eFireplaceStore.
Hy-C - Based in St. Louis, MO, this manufacturer of cost effective chimney caps has been in business since 1947 and offers a multitude of sizing options for most applications.
ICP/Vacu-Stack - A well known name in the chimney cap industry, this manufacturer focuses on production ofhigh quality wind-defeating chimney caps and adapters.
Chimney Cap Materials
Should you order a steel, aluminum, or copper chimney cap? Here's a comparison of the different materials used for building chimney caps so that you can choose the best option for your priorities and budget.
Galvanized Steel: Galvanized steel is a chemically or electrically treated metal that is designed to resist corrosion. There are two options in this category: painted and unpainted. Bare (unpainted) galvanized steel is generally the least expensive, but it only lasts a few years under average use. Painted galvanized steel has a weather and temperature resistant coating that extends the lifespan to 20 years under normal conditions.
Keep in mind that both types of galvanized steel are recommended for areas that are at least 20 miles away from bodies of salt water. A high concentration of salt in the atmosphere will drastically shorten the lifespan of galvanized steel chimney caps.
Aluminum: Although not very common due to its low heat tolerance, Aluminum is very corrosion resistant and even holds up well in areas that have a higher concentration of salt in the air. Aluminum is an ideal choice for keeping debris and small animals out of chimneys that are no longer in use since the low heat tolerance would not be an issue.
Stainless Steel: Stainless steel is extremely corrosion resistant and is one of the most durable chimney cap varieties. Stainless steel chimney caps usually come in one of three grades (430, 304, and 316) which indicate their levels of corrosion resistance.
The least resistant to corrosion is 430 stainless, but although it is considered a "decorative grade" of stainless steel, it still offers significantly better corrosion resistance than carbon steel and can last for many decades. It is not ideal for seaside locations.
The next level is 304 stainless. It has more resistance to corrosion than 430 grade because it includes resistance to acid and chemical staining. The added resistance to acid and chemicals make it ideal for city or industrial areas. It is also the lowest grade acceptable for sea air installations.
The final grade, 316, guards against acid and chemical corrosion to an even higher temperature than 304 stainless. While 304 loses its ability to guard against degradation by acids at about 300 degrees, 316 stainless can remain unaffected up to 500 degrees, making it ideal for flue applications that will see very high temperatures. Used properly, both 304 and 316 stainless caps can easily last for 40 years.
Copper: Like stainless steel, copper is very corrosion resistant. In addition, it dissipates heat quickly and is not prone to thermal warping or damage. Copper chimney caps will start out with a bright metallic color, but eventually patina to a very dark bronze/red color, and finally to a medium green patina. This layer of patina hardens and becomes a very durable shield against further corrosion, making copper caps the longest-lasting chimney cap material.
Copper is the most expensive type of cap, but it is so corrosion resistant that it is unlikely a properly installed copper cap will ever need to be replaced (barring damage from unforeseen weather events).
Guidelines for Choosing Your Mesh Size, Height, and Lid Coverage
Mesh Size: Most caps come with the option of 3/4 inch or 5/8 inch screen mesh. While 3/4 inch mesh offers less resistance to flow, it allows less protection against sparks escaping the flue. The tighter 5/8 inch mesh, commonly called "California mesh", offers better spark protection and is required for use in some states (starting with California). The 3/4 inch mesh is best for cold climates where ice can build up on the screen, while 5/8 is better for dry climates or chimneys with overhanging trees.
Mesh Height: To maintain proper flow, it is necessary to have 5 inches of clearance between the end of the chimney flue and the underside of the chimney lid. While prefabricated push-in caps already have a built-in clearance, it is necessary to consider clearance when purchasing a surface mount cap. Make sure you order a screen that is tall enough to maintain the 5 inch clearance requirement.
Lid Coverage: Ideally, the chimney cap should have a lid large enough to offer 2 1/2 inches of coverage around all sides of the chimney opening. Again, purpose built caps will have this built in, but when ordering tile mount or surface mount caps, keep this measurement in mind. It is recommended to have 4 inches of coverage for caps used in areas that frequently see severe weather with wind-driven rain.
Shipping and Delivery
Most chimney caps are relatively small and lightweight and will be shipped through the normal parcel service. However, if your chimney cap is over 100 pounds or larger than 42 inches, you can expect the chimney cap to ship via a freight semi.
Always inspect your chimney cap as soon as it arrives to check for any damage so that you can make any necessary warranty claims as soon as possible.
Chimney caps are an essential part of protecting your home. Thankfully, there are lots of options to fit your weather conditions, chimney type, and budget. Our chimney calculator at the top of this page is a quick and easy way to sort through the various options. If you have any questions about what kind of chimney cap you should order, feel free to contact us—our technicians would be happy to help!