Rain Caps

Hey Guys-

I see this quite often and finally just have to ask…

Shouldn’t rain caps go on both flues? In this case, one is for the fireplace and the other for the furnace/water heater. Is there a reason not to put one on the fireplace flue? Thanks…


Not rain caps.
They are pest screens as rain caps are not needed.

Please explain.

Both need a pest screen/wire mesh to prevent critters from nesting, etc., correct?

Should one or the other have a rain cap? Why one and not the other?

they just haven’t gotten a squirrel, raccoon or bird down that flue yet…

Explain what Chris?

Are you sure about that? I would guess that one *is *on the fireplace flue. Those caps also double as a spark arrestor, which is required in most areas.

I always recommend rain-caps and pest-screens for masonry-built heat vents. For fireplace flues, spark-arrestors are required in most of CA, and I always recommend rain-caps as well.

I am not concerned about no Rain cap, not required
I am concerned about the chimney it Needs some cement work .
In a cold location not repaired immediatly in two years it could be a ~$750.00 repair

Now there’s a good example of a **** poor chimney cap (“crown” in the US, I believe). In my area, I can go almost a block or more in most areas before I see a proper cap!!

Masonry Chimneys and Fireplaces

There are advantages and disadvantages of capping a masonry chimney or fireplace. Let’s list negative and positive points and then we’ll discuss the different models that are available.

Possible Disadvantages:

  1. Draft Restriction - An improperly designed or installed chimney cap can possibly reduce the draft of a chimney.
  2. Clogging of Screen in Cap - Some chimney caps have small screening which can become clogged with soot and creosote after heavy use. This will cause draft reductions and poor performance of your stove/fireplace.
  3. Discoloration of chimney exterior - In some cases, creosote and tar can collect on the chimney cap and then run down the outside of the chimney structure. This can discolor the stucco or brick. This is usually a problem only with older woodstoves and/or the use of green (unseasoned) wood.
  4. Replacement/Reinstallation - Chimney caps can blow off in high winds. This can destroy the cap or at the very least require another trip on top of the home to reinstall it.

Possible Advantages:

  1. Keeps Animals, especially Raccoons and Birds, from setting up home in your chimney or fireplace.
  2. Keeps Rain and moisture from building up inside chimney. This can help reduce the chimney smell that often invades homes in the warmer weather.
  3. Sheds ice and rain from the chimney crown, which is the cement cover on the top of the chimney structure. This will extend the life of the crown and eliminate some causes of cracking of the flue tile.
  4. Increase draft of chimney, especially in areas with constant wind.

Note about chimney sizes - The three most popular sizes for masonry chimneys are 8" x 8", 8" x 12" and 12" x 12". Many other stock sizes are available. Custom sizes and styles are also produced by many manufacturers.

I’ve always recommended rain caps for both, but wanted to make sure I wasn’t missing something.

I guess I’ve never seen it, but I would think that just a screen mesh over the mechanical masonry flue would still allow a critter to build a nest right on top of it. Whereas, the rain cap would help prevent that.

And yep, the cement crown was bad, like most I see around here.

When I saw this thread, first thing that came to mind was this.
A proper chimney cap would be prudent in the picture and sealant around the chimney flues to provide room of expansion.

Roy took the words out of my mouth on this post.