Ten
Most Common Roof Leak Locations
Roof leaks are a nuisance for
many homeowners. They can be difficult to diagnose – that is a fact. To make matters
worse, different weather conditions will produce leaks in different locations.
The vast majority of roof
coverings operate using the principal of gravity. This can be a big help in
locating a leak source. However, horizontal roof boards can trick you. A leak
may actually be eight to 10 feet sideways from where you see the wet ceiling or
spot in the attic.
Finding the source of some
leaks is easy. Others will require detective work and possibly a garden hose
and an inside spotter. If you don’t feel comfortable on a roof, you will have
to find an honest roofer to assist you. Sometimes this can be as hard as
finding the smallest leak! Here are some tips that may help you find a pesky
roof leak:
The Field of Shingles
If your roof is older, it is
possible that the leak is within the roof field. This means the expanse of
shingles, slate, shakes, whatever. If your roof is asphalt, then you can walk
around with ease. Other materials such as slate, concrete tile or clay tile may
not be so forgiving. You can crack roofing if you walk on it, so be careful.
With regular shingles, look at the tops of the vertical knockouts. Look for
missing colored granules. Look for cracks. Possibly a nail has backed itself
out of the roof sheathing. Simply take your time and hunt.
Valleys
A valley is a line where two
roof planes intersect. Here in Cincinnati we use a metal flashing in the
valleys. Some areas use rolled roofing. Other places simply lace the shingles
together. Valleys can be big problems if you do not trim the shingles
correctly. When you trim a shingle for a valley you end up with a chisel point
on the end of the shingle. If a second cut is not made to make this point like
an arrow point, then water can travel along the top of the shingle and find its
way inside your house. The shingle wrapper tells you how to make this simple
second cut.
Head Wall Flashings
Some roofs stop at a vertical
wall. A metal flashing must be in place to direct water streaming down the wall
away from the stopping point of the shingles. This flashing may be behind wood
siding or in front of a brick wall. The flashing should extend over the
shingles at least three inches. If the wall is brick or other masonry, the
flashing must bend and extend one inch into a mortar joint. Tar, caulk or
roofing cement should never be used in conjunction with these materials. If you
see them, it is a sign that someone tried to patch a leak!
Wall Step Flashing
Some roof leaks happen at
step flashings. You find these flashings where a roof climbs alongside a
vertical wall. As each row of shingles is laid, a step flashing is installed
over the shingle next to the wall. Part of the flashing turns up on the wall
and the other portion gets covered by the next row of shingles. Look for rust
or holes in these flashings. In reality, if all is well, you will be able to
see only the smallest portion of these flashings.
Chimneys
These devils are the source
of many a leak. Chimneys contain four different types of flashing. All must be
right or you will have a leak. Plus, the counterflashing that goes into the
brick mortar joint must be right. A hairline crack above the flashing can allow
vast amounts of water to run behind the flashings. Look for soldered corners of
flashing that might have broken or have holes. Do not use caulk to repair these
flashings!
Plumbing Vent Flashings
Newer vent flashings are a
concern of mine. Many of these incorporate a rubber seal with an aluminum
flashing. The rubber can fail in as little as 10 to 15 years. Look for cracked
rubber around the plumbing pipe. The flashing should dive up and under the shingles
that extend up roof from the middle of the plumbing vent. The bottom half of
the flashing should be exposed and actually cover the shingles.
Furnace or B-Vent Flashing
These flashings are basically
identical to plumbing vent flashings. However, they sometimes have a metal
storm collar. These simply fit tightly around the vertical pipe that exits the
roof. If they become loose, the storm collars can cause leaks.
Ice Dam Leaks
Ice dam leaks plague people
in the snow belt. These leaks can happen even if everything on your roof is
just fine! Ice dams block the natural flow of water down a roof. The water
begins to back up under flashings, shingles, tar paper, etc. Once water begins
to flow into the house, it can drip for days. The only means of prevention is
to install membranes under the roofing. The membranes won’t stop the ice but
will stop water leaks if installed properly.
Wind Blown Rain Leaks
Wind driven rain can also be
a major problem. Once again, you could actually have a good roof and wind will
drive water up and under your roofing materials. The only lines of defense are
tar paper and the ice dam membranes.
If you have metal valleys,
you may want to hem the edges. This means that the hidden edges of the valley
actual have a 180 degree bend. This creates a channel that directs wind blown
rain back to the bottom of the valley.
Roofing cement under shingles
on the edges of roofs that face the wind are also a good idea. Don’t
underestimate the power of a 70 mph sustained wind-driven rain.
Non-Roof Leaks !
Sometimes you think you have
a roof leak when in fact the roof is fine. Attic condensation is a prime
example. High humidity can cause condensation and “rain” to fall in
your attic. It can also make the underside of the roof sheathing look wet. You
think you have a leak instead.
Chimney crowns can develop
cracks. The inside surface of the chimney gets discolored or the plaster
bubbles. You think a roof leak is the cause.
Siding can be missing above a
roof. This can cause water to enter behind head flashings. Be a good gumshoe
and snoop around for the leaks!
