We are by now all familiar with that ubiquitous modern building style, the “mcmansion”, which typically presents a front elevation spiked with gables. In New England, or anywhere where winter brings snow and ice, the issue with converging gable roof valleys is that they present a choke point for snow and ice on the roof, resulting in an ice dam. Such a dam will cause snow melt to back up through a normal shingle roof and leak into the walls and ceilings below.

Ice dam! Note the buildup of snow and ice at the
choke point between the gables.

So it was with this recently constructed residence in Lincoln, Massachusetts. The builder had optimistically laid up asphalt shingles around both gable roofs. This would have worked out fine in Arizona, but not in New England. The first couple of winters after construction were mild but then in the third year there were multiple snow storms in late winter, with seasonable thaws in between. The water poured in and we got the call.

We typically address an ice dam on two fronts. First, to make sure that the roof areas are sufficiently insulated to moderate rapid snow and ice melt. We add insulation where we can, in attics, but where there are lofted, finished ceilings, there is no easy way to augment the insulation.

In such a case it is imperative to present a single impermeable barrier to the water. It could have been membrane but that would destroy the look of the house so we went with fully soldered flat seamed copper. The result is waterproof, and will remain so for a generation, at least.

With that copper element already in the plan, we further suggested to the client that they could enhance the gable design elements by cladding the turret itself in standing seam copper. The finished copper unifies these roof features and highlights the impressive gabled design.

Note the flat seamed copper work below the valley and the standing seam work on
the turret, the copper unifying the design and giving it gravitas.
Detail of the valley transition into the flat seamed copper field.
The specification is for all seams to be “fully soaked” with solder.