Many inspection web sites and blogs offer up a “laugh riot” photo gallery of obvious construction gaffes requiring little explanation. Here, I focus on issues needing lengthier commentary, to illustrate my “deep thought” approach to inspecting. Careful analysis may reveal concerns that aren’t obvious even to experienced inspectors. Conversely, it can suggest that seemingly huge issues aren’t so major after all, or find solutions that are effective without being costly. For complex items, my inspection reports incorporate a level of detail and analysis similar to that shown below.

Where you see replacement shingles, the originals probably came loose because most of the nails were over-driven, punching right through the shingles, a surprisingly common installation defect*. In the left photo, some of the original shingles near the upper right corner, just above the patched area, have slid down about an inch. These will likely be some of the next ones to fall off. Wrinkled shingles above the patched area illustrate the challenge of spot-replacing asphalt shingles. The shingles above have to be lifted and bent quite a bit to nail the replacements. As they get older and stiffer, this becomes harder and harder to do without tearing or breaking them. At some point, spot-replacement becomes unfeasible, so the entire roof slope has to be re-shingled if repair is needed.
     Shingles often fall off in groups, because they are designed to stick together so the lower edges can’t be lifted by the wind, and because over-driven nails tend to be clustered. Shingles may fall off at random times, possibly not starting until the roof is several years old. This can lead to water damage if not repaired right away. If recurring, as has obviously happened on the roof shown at right, it can be a nagging maintenance problem, and may ultimately necessitate premature replacement of the entire roof covering.

Photo at left was a 1949 house, with board roof sheathing, not plywood or OSB. Spacing of shingle cracks matched the width of the roof boards. This house had an old kitchen exhaust fan that was vented into the attic (kitchen and bath fans should be vented to the exterior).  This would typically carry lots of humid air into the attic, especially if used while cooking. I suspected that the cracks, which were concentrated close above the exhaust fan (there were a few much smaller ones in other areas), were caused by expansion and contraction of the roof boards due to moisture from the exhaust fan. In cold weather, the moisture would condense on the underside of the roof sheathing. There were no such cracks on the lower several feet of the roof. I hypothesized that the cracking occurred when ice dams covered the lower several feet of the roof. The ice would have glued the shingles into a monolithic mass that resisted the stress from expansion and contraction of the roof boards directly beneath. The stress was therefore concentrated just above the ice-covered area, which would have varied in width over time, causing cracks to form at different levels.
I couldn’t see whether the cracks extended through all layers of shingles (cracks weren’t visible in the tarpaper underlayment, at the shrinkage gaps between the roof boards). There was generalized staining in the attic, which looked more like it was from condensation than from water penetration. There were no stains on the ceilings below, which didn’t appear to have been painted recently. I advised my client that there was a fair chance (though by no means a guarantee) that if the kitchen exhaust fan was vented to the exterior, the roof would serve for another decade or more (the shingles were only a few years old). The client, a mechanical engineer, thought my analysis seemed sound, and decided to take a chance on this roof. When he hired me for another inspection four years later, he said he had re-vented the exhaust fan to the exterior, but hadn’t had to replace the roof.

Re-configuring the kitchen exhaust fan to vent to the exterior eliminated a major air bypass and undoubtedly reduced ice damming, which is a big problem for many homeowners. Ice damming is caused mostly by warm air from living areas leaking into the attic and accelerating the melting of snow. Warmer air in the attic rises, making upper roof areas a little warmer than lower ones. Within a certain outside temperature range a bit below freezing, snow melts off of upper roof areas, runs downslope, and re-freezes on slightly cooler surfaces below, often building up enough to create a “dam.” If enough water collects just upslope from the ice dam, it can seep between the roof shingles. A waterproof membrane under the shingles in ice-dam prone areas can prevent water penetration, but doesn’t always extend to all the needed areas.

A new entrance was added to this older home to create a separate basement living space. The heavy ice covering made the stairway unusable in winter. A roof slope drained over the open stairwell, so regular shoveling wouldn’t be enough to keep the stairs ice-free. Melting snow would drip off the roof and re-freeze on the stairs. And in summer the open stairwell might funnel rainwater into the basement.
The foundation footing almost certainly now lacked “frost depth.” The bottom of the footing (about a foot below the bottom of the stairwell in the photo) should have 42” of soil cover in the Twin Cities area, to put it below the likely maximum depth that the ground will freeze to. Frozen soil will expand if wet, and could lift the foundation, causing cracks. In the long term, freeze-thaw cycles could cause serious damage.
With a full enclosure over the stairway and good drainage to direct water away from the area, I would be much less concerned about the lack of proper frost depth. An enclosure would help keep the soil from freezing under the footing. If it did freeze a little, but the soil was fairly dry, there would be little soil expansion and therefore little foundation damage. The boulder retaining wall needed to be removed to make room for a foundation to support a full enclosure. Or the new entrance could have been removed, the foundation opening repaired, and the hole filled in.

For many years, central roof drains were commonly run down through the building and into the city sewer system. In St. Paul, as in most cities hereabouts, that is now discouraged because it adds to the volume of water needing to be handled at costly sewage treatment plants. Property owners are charged a premium to leave such systems in place where alternatives aren’t feasible. However, I wouldn’t call this alternative, probably installed when the roof was replaced recently, “feasible.” What happens in winter? The pipe will likely freeze up and lots more water will accumulate on the roof. In this case, secondary drainage would kick in, but only after several inches of water had accumulated, and possibly more if blocked by ice. This could be a serious structural concern. The pipe terminates right at the city sidewalk (last photo). This will make the sidewalk chronically icy in colder weather. In addition, the pipe will probably eventually be cracked and broken by ice within. If the pipe breaks just outside the foundation, it could flood the basement or cause foundation damage. To eliminate the connection to the city sewer, I’d have preferred that things be re-configured so the roof drained off the back of the building, without going through the interior. The yard off the SE corner of the building had plenty of space, and the southern exposure would minimize freeze-up problems. This would have required re-sloping the roof (an expense to be sure, but probably not as big a deal as it might sound; tapered foam insulation board is often used to insulate flat roofs when re-roofing, while maintaining a drainage slope).

Windows sometimes fly under the radar, or try to. Complete window replacement can cost more than a new roof. In one common scenario, seller has disclosed a few inoperable windows, but when I try to operate them, it turns out that many more operate poorly or with great difficulty. Missing or broken sash hold-up devices can be hazardous. With casement windows, cranks may be stripped or well on their way. Replacement parts may not be available. Even if repair is possible, it might yield only borderline-acceptable results, or not be cost-effective due to age of the windows.