Several times a year I get panicked calls from homeowners in communities that have had a lot of two-story housing built over the past few years. All of these problems could have been prevented by vigilant building inspection process that would have exercised a little common sense.
Slope does matters and despite all the good intentions of an architect on how to make a pretty design, some houses are just train-wrecks from a remodelers standpoint. Designing a roof to be unique or creative so that it looks unusual is usually a bad idea. A roof lines should be built with an understanding on how a roof will manage water.
There are three main culprits:
Roofs that terminate into walls
Gravity will always win and when a roof is sloped toward an exterior wall, eventually, even with the best flashing in the world, a leak will occur. Bottom line — never buy a house with a roof that slopes toward a wall.
Roofs that end where a wall meets a valley
When two pieces (facets) of roofing meet, it’s called a valley. In cold weather climates, these areas should always have metal flashing that goes under the shingle. Here in Wisconsin, that is critical since melting ice becomes water and a metal “W” flashing, if properly installed, is impenetrable. The most common example of how this is a problem is on colonial style houses that have garages that protrude from the line of the house. (Attached garages that are several feet in front of the house itself.) Ice builds up in these areas and with freeze/thaw cycles, can back up under the shingles to create ice dams. If your roofer put a rubberized layer of ice/water barrier under the metal flashing, you are better protected, but still it’s not a fail-safe.
Roofs with excessive dormers
We see this a lot in communities like Oak Creek, Franklin and Waukesha in homes that have three or more dormers on the front of the house. The sides of dormers are notorious for having problems. This doesn’t have to be a problem if your installer put 3′ of ice/water barrier on either side of the dormer, but because builders are often building with price in mind, that step sometimes gets skipped.
9 times out of 10 I get a call from a homeowner who is desperate for a roofing repair to these areas. Unfortunately, repair-only should never be considered as the main option because the only solution, short of changing the roof line, is to use an excessive amount of a rubberized ice/water membrane. That membrane allows nails to self-seal around the membrane when a shingle is applied over them. When you remove the shingle, you leave a hole in the membrane underneath. The ice/water membranes come in 3′ wide rolls which, if you want the best protection, should be as close to continuous as possible. If you are doing a roof repair, despite the fact that the shingles may look great afterwards, you will never get full protective coverage of those areas.