Local chimney chase cover replacement in Nassau Village-Ratliff

A quarter inch per foot away from the pipe

One fireplace maker's manual gives the minimum fall for a chase top: at least 1/4 inch per foot, sloping down away from the pipe opening. That may look slight, but it is enough to keep water moving on sheet metal as long as the sheet is stiff enough to hold its shape. A slope that reverses anywhere, even over a few inches, creates a low spot where water sits and the metal stays wet. A level goes on the finished top in several directions, and on a larger chase the sheet gauge is chosen so the slope holds across the span between the supports.

Laying out a top for two pipes

When two pipes share a chase, the top needs two holes, two collars and a layout that lets water flow around both. Each pipe's center is measured from two fixed sides of the chase, because the old cover's holes may be off. The slope or cross-breaks are arranged so neither collar sits in a low spot between them. Spacing between the terminations themselves also matters, since smoke from one outlet can spill into another that sits too close. The fireplace manuals give that spacing, some as a minimum distance and a height difference, and we compare the pair on your roof against the numbers for your models.

Color finishes and what sits under them

Some owners want the chase top to match the roof or the trim. Painted and powder-coated finishes can be ordered on several metals, and the color is chosen with you. The finish is cosmetic. It protects the surface until it is scratched, chipped by a ladder or worn at a fold, and after that the metal underneath is what resists the weather.

So we choose the metal and gauge for the exposure first and add the color second, rather than letting a paint finish stand in for a better metal. A touch-up of chips during later chimney service keeps the finish looking right.