"If it's not broken, don't fix it" is a reasonable rule that saves
time and money on many parts of a house. But not on the roof.
A roof beginning to show signs of wear needs attention.
Wait too long to replace it, and a roof near the end of its useful life can
develop widespread leaks that cause extensive damage. (Reroof too soon, and you
waste years of service.)
The timing can be tricky even when you know what to look for. This
column examines flat and sloped asphalt roofs; and wood, metal, slate and tile
roofs.
Safety comes first
A close look always provides the best information. But you have to measure
that benefit against the risks of climbing around on a sloped roof.
Flat roofs should not be a problem if you can get to them safely. The same
goes for most low-slope roofs that are walkable. That means you can move around
on the surface without scaffolding. (Even then, of course, some people might not
feel safe and should stay on the ground.)
In all cases, you should stay off a roof that is wet, and wear shoes with
non-slip soles even on a dry roof.
If you inspect the surface in warm weather, make the trip early or late in
the day to avoid marring the roof with footprints. Most asphalt-based roofs
become gooey under midday sun.
On more steeply sloped roofs you probably can check the eaves from a ladder.
To examine other areas, resort to binoculars. And if your neighbors start
laughing as you bring your shingles into focus, tell them you're bird-watching.
Basic inspection
points
All types of roofing have some common components. One of the most
obvious, even from the ground, is flashing -- the strips of metal that shed
water at seams between the main roof and other surfaces.
Flashing should lie flat and tuck neatly under roofing and into other
adjacent materials. Loose flashing that has pulled away from one of the mating
surfaces can cause water to drain directly into the house even if the roofing
material is sound.
This situation is most likely to occur around chimneys and skylights. Flashed
seams, including valleys, should be free of debris.
Where you spot a pileup of twigs and leaves, water could be working under the
roof.
And although they're technically not part of the roof, also check the
gutters. Clean out obvious blockages, if necessary, and flood the system with
water from a garden hose to be sure it drains freely. If the gutters clog, even
a new roof can leak along the eaves, particularly in winter.
Flat and low-slope
roofs
Installations and environments vary from house to house on all types of
roofing, sometimes a lot.
Flat roofs, for example, can be built up with layers of asphalt sheets and
tar, or, on newer houses, they can be covered with sheets of rubbery-looking
material, generally called single-ply or modified-bitumen roofing.
In either case, there are two main tip-offs to problems: bubbling and ponding.
Both can be fixed easily enough if they are isolated, but not if they are
widespread.
Bubbles, or air pockets, indicate that the roofing has lost adhesions. If you
push on the bubbles, which often run six inches across or more, you might hear a
squishing sound as a result of the leaks.
Ponding occurs to some extent on most flat roofs. But if more than 15 percent
of the roof area stays covered with water 24 hours after the rain stops, you
should look into corrective repairs and improvements.
If depressions seem spongy underfoot, leaks already could have delaminated or
rotted the roof decking.
Checking other asphalt
roofs
Most sloped roofs with asphalt shingles last about 20 years, depending on
their weight, the roof shape and slope, and other factors. But both high-end and
standard-quality shingles generally show the same four stages of deterioration.
First, surface granules begin to wash off some shingles and collect where
downspouts empty onto the ground. No problems yet.
Second, more granule loss exposes bare spots of asphalt that are easy to see
on light-colored roofs. (The base of all asphalt shingles is dark; it's the
surface granules that provide color.) This is the beginning of the end, and a
good to time to start planning a reroofing project.
In the third stage, shingle tabs (the parts exposed to the weather) become
brittle and start to curl. Before you reroof, these tabs should be removed and
replaced, or the new shingles won't lie flat.
That's easy enough to do here and there. But if many shingles are curled, you
should strip the roof and start from scratch.
If a reroofing job (putting one layer on top of another) looks wavy with a
waffled pattern along the tabs that you can see clearly from the ground, it
won't last as long as it should. To interlock and seal out the weather,
reroofing shingles (limited to one extra layer) need to lie flat.
If you haven't reroofed yet, expect some leaks when shingles hit the fourth
stage of deterioration. That's when the curling tabs crack, break off and expose
nails holding the shingles underneath.
Nails are necessary to hold down shingles, but they make a lot of holes in
the roof that water will seep through.
If your house is shielded by one of the many alternatives to asphalt
shingles, the most popular covering, it can be difficult to tell how long the
roof will last and when you should start thinking about replacement.
Let's look now at the more expensive and more durable -- but often more
unpredictable -- alternatives: wood, metal, slate and tile.
First, a reminder about safety. Even though you get the best information
about a roof from a close look, you should think twice about climbing around on
these materials.
One rule of thumb is to stay off any roof that is not walkable, that is, one
on which you'd need scaffolding to avoid falling off. Also bear in mind that
wood shingles, metal, slate and tile do not offer the grip provided by the
granular coating on asphalt shingles. Some shingles might be brittle and could
break underfoot. In most cases, it's best to leave a close inspection to a pro,
and make your diagnosis from a safe vantage point.
Here are two tips that can help on any roof if you are inspecting from a
distance: Use binoculars to check details, and zero in on the southern exposure.
Although northern slopes generally take the brunt of wind and rain, south-facing
slopes often break down first because of accelerated aging caused by the sun's
rays.
Wood shingles and
shakes
Longevity varies with all types of roofing depending on the installation,
quality of materials and exposure. But many roofs with wood shingles (they're
thinner and sawed) and wood shakes (they're thicker and split) last 25 to 30
years.
Weather works on wood in two ways, causing deterioration from wetness and
dryness. In damp locations, where the roof is shielded from wind and sun, wood
may rot in 15 years or less. The process accelerates when moss grows on the roof
because the spongy patches hold moisture next to the wood even on dry days.
More gradual (and expected) wear occurs with exposure to wind and the sun's
ultraviolet rays that cause drying. Eventually, the drying causes cracking,
which can split a shingle into two or more pieces, often in line with the nail
holes. In the next stage of deterioration, shingles start to curl and no longer
lie flat on the roof.
You can repair isolated damage by removing split sections and installing new
shingles. But, as a general guide, when one-third of the surface shows some
deformation from cracking and curling, it's time to think about replacement.
Metal roofing
There are many varieties and styles of metal roofing, including steel,
aluminum and copper. And although each type wears a bit differently, many sheet
metals last 50 years or more. They look nice too, but longevity is the main
reason for investing in them.
Most metal sheets are sealed with standing seams that rarely cause problems
if installed well because the edges are joined in several overlapping layers.
You're more likely to have problems where the roof is flashed against siding or
a chimney, and from a variety of chemical reactions that can cause rusting and
pitting.
There are two common types of these reactions. One is caused by contact with
pollutants including acid rain, acids in moss and other growths, and alkalies
that may leach out of nearby masonry walls. The other is caused by installation
faults that set one type of metal against another, for instance, setting iron
fittings or steel nails in copper sheets. This causes galvanic reactions that
can lead to rusting.
Preventing these reactions makes a roof last longer and minimizes repairs,
which often are difficult and expensive to make unobtrusively. Roof coatings can
help with pitting and pinhole leaks, but pretty much kill the elegant look of a
standing-seam roof.
Slate, clay tile and
masonry shingles
These very durable materials should last as long as the structure. And they
generally have a lot of structure to rely on because their weight and rigidity
require an extremely strong support. If you wanted to switch from standard
asphalt shingles to barrel tile, for instance, in most houses you would have to
reinforce or even rebuild the existing roof structure.
There are several signs of problems you can spot, mainly crazing and surface
cracking and moss growth. Or possibly shards of slate sliding off the roof onto
the yard.
These systems almost always require professional attention -- by a contractor
experienced with masonry roofing as opposed to asphalt shingles.
The rate and degree of deterioration also depend on material quality. For
example, some softer slates erode from pollutants in air and rain, particularly
at nail holes. In cold weather, both slate and tile can crack from ice-dam
pressure or the fall of a branch that would damage but not break more flexible
roofing.
Some of the most inexpensive roofing tiles also will develop surface cracks
(crazing) and lose patches of surface material (spalling) during freeze-thaw
cycles because of inadequate firing when they are manufactured.
One of the most common problems is moss growth. In the right conditions, it
can latch onto the smoothest slate or cement-based shingles. Of course, moss
clings to stone in natural surroundings with little effect. But on roofs, it can
pull water by capillary action under the shingles, where it can rot the
supporting structure.
