Caps, Dampers and Waterproofing in Alpine

Three separate jobs get bundled under this heading, and it helps to keep them apart.

The cap, and why the fastenings matter more than the cap

A cap keeps rain and snow out of the flue, stops birds and rodents nesting in it, and arrests sparks on their way out. Any decent cap does those things. What separates one that lasts from one that does not, on ground like Alpine's, is how it is attached and what it is made of.

Air moving down off the mountain in the evening does not just push. It lifts, and it vibrates. A cap held on by friction fit or a couple of short screws works loose over a season of that, and once it starts moving it wears its own fixing holes. We fit stainless caps with mechanical fasteners into sound masonry, and we size the shroud so the mesh area is large enough that the cap does not restrict draft on a long flue. On the taller stacks around town we prefer a shroud that is engineered for the flue size rather than a universal one that happens to sit over it.

Dampers, and where the heat is going

The throat damper at the bottom of an old fireplace is a cast plate that warps with heat and rusts with condensation, and by middle age it rarely closes to anything like a seal. Meanwhile the flue above it is a hole in your roof. A top-sealing damper mounts at the crown with a silicone gasket and a cable down to the firebox, and closes the chimney at the top instead of the bottom. In a house at Alpine's elevation, with a long heating season, that is a genuine and continuous reduction in the amount of conditioned air leaving through the fireplace. It also keeps the flue dry between burns, which slows corrosion at the top.

Waterproofing, done the right way round

Water gets into masonry through the crown, through eroded joints and through the face of the brick itself. Sealing is the last step, never the first: apply a sealer over an open crack and you have waterproofed the water in. We repair first, then apply a vapor-permeable siloxane treatment that stops liquid water entering while still letting vapor escape. A film-forming coating traps moisture behind it, and in a place with as many freeze-thaw nights as Alpine that accelerates exactly the damage it was bought to prevent.

Chase covers on framed chimneys

Not every chimney here is masonry. Framed chases carry a metal cover, and the flat, thin ones pond water and rust through from the inside. A replacement in stainless with a cross-break to shed water and a proper drip edge solves it permanently.