Sizing and Installation Guide for Standard Chimney Cap Sizes

I have been installing Gelco caps for over 25 years now and can attest to their quality. These are constructed well and have a large top cover for rain deflection. You will need to take a measurement of the exterior length and width of the flue tile(s) that you intend to install the cap(s) on; each cap size will fit a range of measurements of outside flue tile dimensions.. For example, a 12″ x 12″ cap has a fit range of 10″ x 10.5″ to 12.5″ x 13″ A lifetime warranty is available. Standard sizes are:

• 8″ x 8″ (fits outside tile dimensions 6.25″ x 6.25″ to 8.5″ x 8.5″)
• 8″ x 13″
  (fits outside tile dimensions 6.25″ x 11.5″ to 8.5″ x 13.5″)
• 8″ x 17″
  (fits outside tile dimensions 6.25″ x 16.5″ to 8.5″ x 18.5″)
• 13″ x 13″
  (fits outside tile dimensions 11.5″ x 11.5″ to 13.5″ x 13.5″)
• 13″ x 17″
  (fits outside tile dimensions11″ x 16.5″ to 13.5″ x 18.5″)
• 17″ x 17″
  (fits outside tile dimensions 11″ x 16.5″ to 13.5″ x 18.5″)

IMPORTANT NOTE: some of the older flue tiles were made of pumice and were square or rectangular. Then the tile manufacturing switched to terra cotta and began rounding the corners of the tiles. The 8″ x 12″ and 8″ x 16″ tiles actually became ovals.

When it comes to the newer tiles with rounded corners, you want to order a cap that is closet to the actual outside dimensions of the tile. When I come across these newer tiles, I order A 12′ x 12″ cap for a newer tile that has rounded corners and outside dimensions of 12′ x 12″. The 13″ x 13″ listed above, even though its range of fit is appropriate, DOES NOT FIT WELL ON THE NEWER TILE.
I order A 12′ x 16″ cap for a newer tile that has rounded corners and outside dimensions of 12′ x 16″. Gelco does manufacture to these dimensions, but you may have to request them from the retailer by phone, as they may not have them listed on their website. The 8″ x 17″ Gelco black galvanized cap will fit the older and newer tiles well.

Your chimney needs to be in good repair before installing a rain cover. Rain covers attached to a flue tile that is not properly cemented to the top of the chimney can blow off in a good wind storm, taking the flue tile it is attached to with it (I’ve seen it happen). Any loose brickwork or chimney cap (crown) issues should be repaired first.

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