Chimney Caps

What a cap does

• Rain. An open flue is a hole in the roof. Water falling down it rusts the damper, soaks the smoke chamber and wears the flue lining.
• Animals and debris. Birds, raccoons and squirrels use open chimneys, and leaves collect on the smoke shelf. See animals and nests in the chimney.
• Sparks. A screen keeps larger embers from landing on the roof or nearby.
• Downdrafts. On some chimneys, a cap can reduce wind blowing down the flue, though it isn't a cure for every draft problem.

A cap is not the same as a crown. The cap is the metal cover; the crown is the masonry slab it sits on. Our crown vs. cap guide explains both.

Single-flue or full-width?

Caps also come in different metals. Galvanized steel costs less but can rust; stainless steel and copper last longer in wet, salty or acidic conditions. Flues that vent gas or oil appliances can be harder on metal because of acidic condensation.

Signs you need a cap or a new one

• No cap at all, or you can see straight into the flue from the ground
• Rust streaks on the crown or brick below the cap
• A cap that's tilted, loose, or missing its screen
• Water or rust flakes on the damper after rain
• Animal noises, nesting material, or debris in the fireplace
• A screen clogged with soot or creosote, which can restrict draft

How we assess it

From the roof, when it's safe, we check whether there's a cap, what condition it's in, and how it's attached. We measure each flue tile and the crown, check how far the tiles project, and look at the crown underneath, since a cap can't make up for a cracked crown. We note which appliance each flue serves, because a flue venting a furnace or water heater may need a cap made for that use.

Inside, a look at the damper and a chimney camera, where the flue allows, show whether water or animals have already caused damage. You get photos and our findings, with cap options for your chimney, before any work is scheduled.

Repair or replace?

A cap that's still solid sometimes just needs to be reattached, or have a bent screen straightened or a clogged screen cleaned. That's worth doing when the metal itself is in good shape.

Replacement makes more sense when:

• The body or lid is rusted through
• The screen is torn or corroded and can't be cleaned
• The cap is the wrong size or type for the flue or appliance
• The flue tile it clamps to is cracked, so a full-width cap fastened to the crown or chimney is the better choice

Wind, animals and fuel type

Where wind blows smoke back down the flue, some caps are designed to reduce downdrafts. They can help when wind is the cause, but smoke spilling into the room has many possible causes, from an oversized fireplace opening to a house that's short of air. See why smoke comes into the room before assuming a cap will fix it.

If an animal is already living in the flue, it has to be removed before a cap goes on, or it will be trapped. That's covered on our animal removal page.

Appliance manufacturers sometimes specify the termination cap for their venting systems. On factory-built chimneys and gas vents, the cap is typically part of the listed system, so a replacement should match the manufacturer's specification.

Chimneys with more than one flue

Many New Jersey homes have a chimney with two or three flues side by side: one for the fireplace, one for the furnace or boiler, and sometimes one for a water heater or a second fireplace. That changes the cap decision.

• Flues that sit close together often can't each take a single-flue cap without crowding.
• Flue tiles of different heights can make a full-width cap harder to fit, and sometimes a tile has to be adjusted.
• Exhaust from one flue shouldn't be drawn down into the next. Flue height differences and the cap design both play a part.
• A flue that vents a gas or oil appliance may need a cap suited to that appliance, which isn't always the same as the fireplace cap.

A full-width cap is often the tidiest solution for a multi-flue chimney, and it shelters the crown as well. We'll measure each flue and show you the options that fit.

What affects the scope

• Number, size and height of flues
• Condition of the flue tiles and crown
• Metal type
• Whether a custom-sized full-width cap is needed
• Roof access and chimney height

A cap keeps rain out of the flue. It doesn't stop water entering through the brick, crown or flashing. For leaks, see chimney leak repair.

Next step

If your chimney has no cap, a damaged one, or signs of water or animals in the flue, request an assessment. A photo of the top of the chimney helps. A team member will contact you to confirm a time.

Request a chimney cap assessment

Questions homeowners ask