Been told you need to buy a chimney chase cover? Well if you're looking to learn why you should or shouldn't, or need to know more about which type to buy, then read on, friends.
First, let's get some terminology straight.
The chimney chase is the exterior top of the chimney - the decorative part that you see from the outside - when you do not have a solid masonry chimney.
The chimney chase cover is a metal fabricated cap designed to fit on top of your chimney chase.
Chase covers are not for masonry chimneys: they are for the boxes (chases) that house a factory built chimney.
The purpose of the chimney chase cover is to keep rain, debris, and animals out - and these are really things you don't want in your chimney.
So cover up.
Size You want to buy a cover that fits perfectly.
If it doesn't fit just right, things will get inside - and then what's the point, right? You should allow about ¼ to ½ inch all the way around, and the cover should be spaced off the chase by about an eighth to ¼ of an inch.
This ensures the cover isn't too tight to install but protects the entire top of your chimney from small animals while leaving enough space to allow for a little ventilation.
(A chase cover that's too tight traps moisture which can rot away the house.
) Material The material used matter too.
Chase covers can be constructed from copper, aluminum, stainless and galvanized steel and copper, and each of these types has something different to offer.

• Copper is truly the top quality choices, and the price tag will reflect it.
  Copper chase covers are generally so expensive that only very expensive houses warrant getting them.
  
• Galvanized steel is always the lowest cost, but it rusts quickly and doesn't last long.
  We recommend against it.
  
• Aluminum will not rust, but is also not very strong.
  It's often not readily available in the sizes necessary either.
  
• Stainless steel is the strongest of your choices.
  It lasts long and is cheaper than copper - stainless steel chases it usually get our nod.
  

Design The design is another consideration.
You'll also want cross-breaks in your cover, These look like a big X from corner to corner and keep the cover from catering and collecting water (which is in fact why most galvanized chase covers need to be replaced.
) There's also the side drop and collar to consider.
The sides usually range between two and six inches, while three or four inches is pretty standard.
While a top collar (around the hole that the chimney comes up through) isn't actually required, it's a nice feature of a good chase cover; they're usually 2 inches tall.
Looks The chimney chase has historically been considered more function than aesthetics.
Lately, we've been seeing a lot more color choices though.
So you may be able to get it in a color that goes well with the house.
You could also paint it, but that means you'll likely have to repaint at some point, so keep that in mind.
Remember that it is smarter and more cost effective to buy a quality piece now.
When purchased wisely and installed correctly, chimney cover will last for a very long time.