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Installing Stainless Steel Chimney Rain Cap On Flue Vent

Updated on October 16, 2013

Single Flue Chimney Rain Cap, Clay Tile Mount

Where To Start

When hurricane winds strike, cheap chimney rain caps are likely to blow off and expose your chimney to harsh elements. Inexpensive chimney rain caps are likely to rust causing them to be defective. When replacing a chimney cap, it is important to make an informed decision to purchase the correct cap for the chimney. There are various styles of chimneys and flues, and there is a rain cap to match each application.

We first must familiarize ourselves with the different types of chimneys and flues. A chimney is referred to as the housing and structure and is not what actually is venting the appliance. The flue is what contains the venting emissions. Some homes might already have a rain cap for a flue, but need a cap for the top of the chimney. This can get confusing when the chimney and the flue get Misunderstood. You must determine if your intent is to cover the top of the chimney to prevent leakage, or prevent the elements from entering the flue. A chimney chase cover is designed to cover the top of the chimney to prevent leakage. A chimney Rain cap is designed to prevent elements from entering the flue. In some cases, depending on your setup, you may need to use both a chimney chase cover and a chimney rain cap.

Clay Flue Chimney Caps

The chimney rain cap that would best suit a clay chimney flue is a clay flue chimney cap. The clay flue chimney cap sits on top of the clay flue and will overhang the sides. Located on the side of the chimney cap are pressure screws that force fit the cap to the clay flue. If a chimney flue does not protrude through the top of the chimney, and the cap cannot attach to the outside of the flue, a chimney cap leg kit can be used to pressure fit the cap to the inside of the chimney. For the most part clay chimney flues have standardized sizes. Most clay fluechimney capsare made to adjust to various sizes. Choose the cap that is the closest fit to your clay flue.

Special Circumstances for Clay Flues

For unique size clay flues, a custom made chimney cap can be made. Some chimneys have more than one flue inside the chimney. Sometimes the flues can be too close to each other to use multiple single flue chimney caps. In that case, a multi flue chimney cap can be installed. A multi flue chimney cap can mount to the top of any chimney, or to the outside of any chimney to covering all the flues.


Chimney Rain Caps That Prevent Wind Related Down Draft

Homes that are nearby hilly landscape, close to other building or by tall trees can create negative pressure inside the home which causes a down draft in the chimney. While having a fire inside the home, a down draft can cause the fireplace or wood stove to be smoky. There are chimney rain caps designed to prevent a wind related down draft. A Vacu-Stack chimney cap is the premier chimney rain cap to prevent a wind related down draft. The Vacu-Stack chimney cap is designed to cyclone the wind that hits the cap creating an updraft. This cap can be installed on brick and mortar chimneys, air cooled chimneys, and Class A chimneys.

When choosing what size Vacu-stack cap is needed, determine the size of the smoke exit hole of the appliance that is being vented. The Vacu-Stack should not be less in area than the appliance. For a traditional fireplace, the Vacu-stack should be no less than 10% of the area of the face of the fireplace. Note, the Vacu-stack rain cap will not induce the draft for your fireplace or wood stove; the sole intent is to prevent against wind related down draft.

Another chimney cap that prevents a wind related down draft is the Wind Directional Flue Cap Terra Cotta Mount. The wind directional cap can freely rotate around its shaft. When wind blows, the fin aligns the hood against wind so the front skirt will divert all air streams. All debris will be sent over the top and sides of the cap solving wind related downdraft problems. Also, when wind flows over the cap, it creates low air pressure over the flue due to the speed difference of air inside and outside of the flue. This effect helps the flue to draw air more efficiently. The streamlined shape of the cap slices through air with very little resistance and it can withstand very strong winds.

Weather Shield Chimney Rain Cap

Aftermarket Manufacturer Caps- Air Cooled and Class A

Air cooled and Class A chimneys are becoming more and more common with newer construction. Air cooled and Class A chimneys generally vent zero clearance gas or wood burning fireplaces. This style chimney pipe is designed to be within 2 inches from combustible material. The air cooled chimney pipe has 2 to 3 walls that rely on an air gap that is able to breath at the top of the chimney. That air gap cools the outside wall of the chimney pipe, cooling the pipe from getting too hot. Air cooled and Class A chimneys generally require the manufacturer cap. Trying to match the manufacturer cap can be difficult; however there are aftermarket chimney rain caps that work for those types of systems.

The weather shield chimney cap is the premier aftermarket chimney cap for those chimney systems. The weather shield chimney cap can come as an air cooled cap or a standard Class A chimney cap. The weather shield air cooled chimney cap has spacers to allow the outer pipes of the chimney to breath, while venting the main exhaust. The weather shield standard cap is made for Class A chimneys. Both the air cooled and standard weather shield caps do a great job of keeping rain out of the of the chimney while having a wire screen to prevent sparks from exiting the cap as well as preventing critters from entering the chimney. Weather shield chimney rain caps come in various sizes- almost guaranteed to fit any chimney pipe.

Round Flexible Liner Rain Cap

Top Plate Mount

There are some chimney rain caps that can only be used for certain applications. Chimney rain caps that are marked "Top Plate Mount" can only be used in conjunction with a flexible chimney liner application. The components that are provided with a flexible liner are made to work around a flexible liner. For example, a 6” flexible liner will have an outer diameter of 6.25”. The 6” flexible liner will be going inside a top plate at the top of the chimney. The top plate’s collar diameter measures 6.75”. The chimney rain cap that will fit on the top plate will measure 6.825”. When a top plate mount chimney cap is labeled as 6”, the rain cap will actually measure 6.825”, and will not work with a 6” diameter pipe. All the sizes for the top plate mount rain cap will be scaled to those sizes.

Make The Right Choice

Purchasing a stainless steel chimney rain cap will stand the test of time. Cheap economical chimney rain cap will eventually rust and blow off the chimney. A stainless steel chimney rain cap will ensure you make a one-time fix that any DIY homeowner can do for themselves. All of the chimney caps described above are made of stainless steel.


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      Ahmad 3 years ago

      This is too funny .Here is my version : One day my cat was very intterseed in the extractor fan above my stove top & on closer inspection I could hear rustling & flapping about in the funnel above .When I turned on the fan the above sounds became more urgent . Oh s--t , what to do ????Checked the outside wall vent where the fan directed the air & there was a teeny weeny space , I felt a weeny bird had gotten in & grown to adulthood in there !!Called the fix it man & to my horror , he found a giant RATTY in there.Your version of a few innocent birdies sitting on the couch waiting for tea is much preferred !

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      Calvin 3 years ago

      Firstly you are brave doing it in cold November! Unless you are not from the UK!The quantities I used are all on 5 btcueks of sand (in effect the sand used for the dome was enough!)However I recently spoke to some pros who built an oven at our they recommend 4:1 sand to clay so only enough clay to hold it together and mix in some straw. They say it means less cracking. I may try that next season and do a page on the diffference.