Chimney Cap Installation in Sherman Oaks, Sized to the Code

The residential building code describes a chimney spark arrestor in four requirements, and each one has a practical reason. The screen's net free area has to be at least four times the flue's, so the cap does not choke the draft. The screen must resist heat and corrosion at least as well as 19 gauge galvanized steel or 24 gauge stainless, because thin hardware cloth burns through or rusts out within a few seasons. The openings must stop a sphere larger than 1/2 inch from passing, without blocking one smaller than 3/8 inch, which is tight enough to hold back burning embers and open enough not to clog with soot. And the arrestor has to be accessible for cleaning, with a screen or cap that comes off so the flue can be swept. Caps sold off the shelf often miss one of the four, most often the mesh size or the free area. Ours are stainless caps that meet all four, and the quote names the cap and the flue size it fits.

Here is where the rule bites in Sherman Oaks. On the flat streets north of Ventura Boulevard, a cap is mostly about rain, birds and raccoons. In the hills south of the boulevard, and west through Encino and Woodland Hills or east into Studio City along the Santa Monica Mountains, many homes sit in mapped very high fire hazard severity zones, and the arrestor becomes a fire safety item. Fire department brush clearance rules in those zones call for an approved spark arrestor on chimneys, and insurers writing policies there sometimes ask for a photo of the chimney top. After the 2018 Woolsey Fire and the January 2025 fires, that question gets asked more often. A cap that meets the rule, photographed after install with the mesh visible, answers it. We send those photos with the invoice, so you have them on file when the question comes.

Caps come in two basic types. A single-flue cap clamps or screws onto one flue tile that stands above the crown. The other kind, a crown-mount or multi-flue cap, spans every flue at once and is anchored into the crown itself. That type suits older Valley chimneys with two or three flues side by side, or a flue tile that is cracked or sits flush with the crown. The choice depends on what we find up top: tile size and shape, crown condition, how close the flues sit to one another, and whether a furnace or water heater shares the chimney with the fireplace. A flue serving a wood fireplace cannot be shared with any other appliance, and a cap must never let exhaust from one flue spill into the next. On a factory-built fireplace, the cap is part of the listed system, so a replacement has to be the maker's listed termination, not a generic masonry cap.

Installed caps run $165 to $670. The low end is a stainless single-flue cap on a standard round or square tile on a one-story roof. The high end is a crown-mount cap built to measure for a multi-flue chimney, or a cap on a steep or tall roof that needs extra access gear. Copper caps and decorative shrouds can be ordered, though on a factory-built chimney the listing limits what goes on top. If the crown under the cap is cracked, we tell you before the cap goes on, because a new cap over a failing crown will not stop a leak. We photograph the top before and after, measure the mesh against the rule, and leave the old cap with you or haul it off. Most installs in Sherman Oaks take an hour or two on the roof once the cap is in hand.