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How to Replace a Rain Cap

Updated: Oct. 31, 2019

Keep your metal chimney dry

FH14FEB_RAINCP_01-2Family Handyman

Older rain caps for metal chimneys and flue liners can deteriorate or fall apart, but installing a replacement cap is as easy as climbing onto the roof.

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Check your rain cap for wear

Photo 1: Check and adjust the fit

Slide the new cap into the flue. If the stub section on the cap is too large, crimp it with a crimping tool.

Photo 2: Level and secure the cap

Plumb the cap so it fits squarely in the flue and secure it with one sheet metal screw. Recheck that the cap is plumb and install two more screws.

High winds, sleet and plain old corrosion can cause a rain cap to break apart, rattle and leak water into your home. If you feel comfortable climbing up on your roof, you can replace the old one yourself for about $40. That’ll save about $150 in labor from an HVAC service company.

You can buy a new rain cap and a sheet metal crimping tool at any home center. Flues are usually 5 or 6 in. in diameter, so buy both size caps and return the unused one. You’ll also need three hex-head or Phillips self-drilling 1-in. sheet metal screws and a drill and bit.

Remove the old rain cap and toss it. Select the correct cap and check the fit (Photo 1). Then secure the new cap (Photo 2).

Required Tools for this Project

Have the necessary tools for this DIY project lined up before you start – you’ll save time and frustration.

  • Cordless drill
  • Crimper

Required Materials for this Project

Avoid last-minute shopping trips by having all your materials ready ahead of time. Here’s a list.

  • 1-in. self-drilling sheet metal screws
  • Rain cap