Caps and Water Control for Midvale Chimneys

The retired chimney

It happens the same way every time. The furnace gets replaced with a high-efficiency unit that vents out through the wall, or the fireplace gets closed off in a remodel, or a family simply stops burning. The stack stays where it is, open at the top, and from that day it never has warm gas passing through it again. That is the worst condition masonry can be in. A working flue dries itself out every time it runs; a disused one holds everything that falls into it and goes into each freeze saturated. We repair chimneys in this city every year that were structurally fine when they were decommissioned and are now a rebuild, and a cap would have prevented most of it.

Water arrives from the top, and shows up somewhere else

Ceiling stains beside a chimney breast are usually blamed on the roof, and they are usually a cracked crown, a missing cap or failed flashing. Water entering at the top travels down the outside of the flue and inside the masonry, and it emerges wherever it meets a surface it can wet. That is why fixing one of the three and not the other two so often fails to stop it, and why we look at the crown, the cap and the flashing together rather than picking the cheapest.

Chase covers and townhome roofs

Framed chases have a metal lid instead of a masonry crown. Builder-grade covers are galvanized, they flatten with age, and they rust through from wherever water sits. Everything beneath is concealed framing, and on attached housing that framing may not stop at your unit. Replacing a failing cover with stainless, formed with a slope and sealed properly around the pipe, is straightforward work with a very good return.

Top-sealing dampers

The original throat damper in a mid-century Midvale fireplace almost certainly leaks. It is a warped iron plate resting in a rusty frame, and it has been letting conditioned air out of the house all year for decades. A damper mounted at the top of the flue seals with a gasket, is operated by a cable from the firebox, and serves as the cap at the same time. On a fireplace you use a few times a winter it is usually the most worthwhile item on the list.