Keeping Weather Out of Highland Chimneys

Something else comes with a city built mostly within the last thirty years: a great many of the chimneys in Highland are framed chases with a sheet-metal chase cover on top rather than brick and mortar. A flat or nearly flat chase cover holds water, and once its seams open, that water runs straight down inside the chase where nobody sees it until the ceiling below starts to stain. The repair is a cross-broken cover with a proper drip edge, not another bead of caulk.

Canyon air does not behave like valley air

Air draining out of a canyon arrives with direction and speed, and it is gusty rather than steady. A gust passing across a flue top can momentarily reverse the pressure at the opening, and the result indoors is a puff of smoke from a fireplace that has never done it before. People assume the chimney has developed a fault. Usually the chimney is the same and the wind found the right angle.

The remedy is at the top. Termination height relative to the roof ridge is the first thing to get right, because a flue that ends inside the turbulent zone rolling off a roofline is fighting a losing battle. After that it is cap geometry: a taller lid with more clearance, or where the site really funnels wind, a directional cap that uses the moving air to draw the flue rather than push it.

Snow, ice and the storm collar

Snow sits longer up here than it does down on the valley floor, and it sits on the flat surfaces of your chimney top. That means meltwater running repeatedly across the crown or the chase cover, refreezing overnight, and working into every seam it finds. The storm collar and its sealant around the flue pipe are a small item that takes the brunt of this, and dried, cracked sealant there is one of the most common leak sources we find on the roof. It costs very little to redo and it is often the entire explanation for a mystery drip.

Dampers, and the ones that were never any good

Most of the rarely-used fireplaces in this city are sitting behind a throat damper that leaks whether it is open or shut. On a big house that is a permanent hole from a heated room to the outside. A top-sealing damper closes with a gasket at the very top of the flue, keeps the whole chimney warmer and drier, and can be operated from the firebox. On a wood fireplace you light twice a winter, it is the single most sensible thing to add.

Waterproofing that lets masonry breathe

Sound stone and brick take a vapor-permeable repellent, which stops liquid water entering while letting the wall dry outward. Anything that forms a shiny film is the wrong product. It traps whatever is already inside, and the next hard freeze takes the face of the masonry with it.