Chimney Cap
A chimney cap is the metal (stainless, copper, galvanized, or aluminum) or cast-stone hood that sits on top of the flue, typically with a mesh screen on the sides. It serves three functions: it keeps rain, snow, and animals out of the flue; it acts as a spark arrestor; and it stops downdrafts that can push smoke back into the home. It is not the same thing as a crown coat — the cap sits on top of the flue tile, while the crown is the cement seal around it.
In depth
Chimney caps degrade in Wisconsin winters: the screen gets clogged by soot and pollen, the fasteners rust, and the hood itself can corrode or dent from ice. A clogged cap is a fire hazard (creosote has nowhere to escape) and a draft problem. Whenever we clean an exterior chimney, we inspect and clean the cap at the same time — otherwise the brushes, wildlife guards, and screens can harbor debris that streaks the fresh bricks the next time it rains.
How this shows up on our jobs
We clean the chimney cap's screen and mesh every time we do an exterior chimney wash, because a dirty cap will streak a freshly cleaned chimney within weeks.
Services where this matters
Related terms
Crown Coat
A crown coat is the sloped mortar or cement cap that sits at the top of a masonry chimney, surrounding the flue tile(s). It is not the decorative cap piece (that's a chimney cap) — it is the poured or troweled waterproof seal that directs rainwater away from the flue and the chimney's interior bricks. A properly built crown coat is two inches thick at the flue, tapered outward to a drip edge overhanging the brick by about two inches, and cast from a waterproof mortar mix or a specialty elastomeric crown-coat product.
Damp Proofing
Damp proofing is the application of a moisture-resistant coating or membrane to a masonry surface — most commonly foundation walls, brick veneer, and chimneys — to slow water absorption and reduce efflorescence, spalling, and interior moisture problems. It is less robust than true waterproofing (which forms a continuous, pressure-rated barrier) but more cost-effective and better-matched to surfaces that need to breathe.
Weep Hole
A weep hole is a small, deliberately-placed opening at the bottom of a brick-veneer wall, window frame, or storefront glazing that lets trapped water drain out. On brick homes, weeps are typically vertical gaps in the mortar every four to six bricks along the bottom course; on vinyl and aluminum windows, they are the small slots in the bottom of the exterior frame. Without weep holes, water that gets behind the brick veneer or inside the window frame has no escape path and causes efflorescence, mold, rot, and interior leaks.