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Chasing Roof Leaks
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THIS SECTION INCLUDES INFORMATION ON HOW TO LOOK FOR LEAKS ON FLAT /
LOW-SLOPE AND STEEP ROOFS.
There can be many reasons for a leak. Leaks can be the result of poor
roof system installation, mechanical damage such as dropped screwdrivers or
knives, plugged roof drains, roofing material failure, HVAC problems; the
list goes on. The source of a leak can be quite distant from where it
actually shows up.
Let’s look at an example. Say there’s a hole in your asphalt
shingles. The water gets in this hole, and then has to run along the top
of the underlayment until it finds a hole there. Then it runs along the
top of the decking until it reaches either a hole in the decking or a
seam. Then it drops down in the attic and will run along the top of the
ceiling until it reaches a hole or seam in the drywall, plaster, etc.
The distance can be lengthened even further if you have more than one
layer of roofing on your building or if you have a vapor retarder at the
ceiling level.
Chasing a leak isn’t always as easy as it would appear to be. When trying
to locate a leak, use the following guidelines to assist you. NOTE: whenever
you see the words "the leak area," it refers to an area within a 10 foot (3
meter) diameter of the leak.
Flat or Low-Slope Roofs
- Inspect any roof drains near the leak area. If they are plugged or
draining slowly, then there is a strong chance that they are the reason
for the leaks. Drains are rarely waterproof if they are plugged. They
are generally designed and constructed for water to flow in one
direction only...down.
- Inspect any material seams in the area of the leak. Just because you
see "tar" or adhesive sticking out under a lap, it doesn’t mean that the
material is adhered properly. Take a flat blade about 2 inches (5 cm)
long (like a pocketknife blade), and gently run it along under the lap.
If it slides in more than 1 inch (2.5 cm), then the seam should be
sealed. If it slides in for the length of the 2 inch blade, it’s a good
suspect for a leak.
- Look carefully at all penetrations for signs of problems. Problems
include holes in the metal flashings, shrunken pitch pan filler,
deteriorated caulking, curled flashing flanges that are sticking up
through the roof membrane, or any other visible defects.
- Look for blisters that have been punctured.
- Look closely at expansion joint seams. These are often faulty.
- Check for splits in the area. Do this by walking the area with your
feet close together and taking many small steps, turning in all
directions. If there is a split, you’ll see the roof separate between
your feet.
- If the leak occurs near the edge of the building, check the edge
metal. It can separate at the seams and tear the roof membrane in the
process.
- Check under debris. A lot times, if debris has been sitting on a roof
for a long period of time, then it can hold water which will expedite
roof deterioration. Bird, rodent, and other vermin nests have been found
under piles of debris on roofs.
- If you get a freak rain storm that dumps horrendous amounts of water
on your roof in a short period of time, and all of a sudden you have
half a dozen leaks where before there were none, don’t get overly
excited. Most roofs are not designed or constructed to handle that much
water all at once.
- If you look carefully, and find nothing on the roof, then check your
attic or ceiling space. What is mistaken for a roof leak can sometimes
be a problem with the plumbing, especially with commercial buildings
because fire sprinkler lines usually run along the attic space. This is
often identified by a leak occurring when it isn’t raining.
- Another problem that is frequently mistaken for a roof leak is a
poorly designed roof-mounted HVAC unit. HVAC units can have faulty pans
in them which will permit water to enter the building during a rain
storm.
Steep Slope Roofs
- Look at all roof penetrations in the leak area closely for holes and /
or damage.
- Look for "shiners." Shiners are nails that were not covered by the
following course of roofing material. If left exposed too long, many
nails will rust, leaving a hole and causing leaks.
- Look at the mortar on chimneys and parapet walls. It’s rare, but
damaged mortar can cause leaks.
- If your building has a stucco facade, then cracks in the stucco,
especially along the tops of walls, can be the source of leaks.
- Check to make sure that all drain details are functioning and that
your gutter is not full of debris. If your edge details and gutter
details are not done correctly, water can back up over the top of the
fascia, run along the soffit, and down the inside of the wall where it
enters your building.
- If you look carefully, and find nothing on the roof, then check your
attic or ceiling space. What looks like a roof leak can be a problem
with the plumbing, especially with commercial buildings because fire
sprinkler lines usually run along the attic space. This is often
identified by a leak occurring when it isn’t raining.
- Another problem frequently mistaken for a roof leak is a poorly
designed roof-mounted HVAC unit. HVAC units can have faulty pans in them
which can permit water to enter the building during a rain storm.
- Look for areas where there is a lot of debris such as leaves and
branches that have gathered. Piles of debris can block water flow which
can cause the water to back up under the roofing. This commonly occured
behind chimneys and in valleys.
If you are calling a contractor to take care of your leaks. Here are some
questions that he may want to ask you.
Q: Has anyone been on your roof doing work? An
electrical contractor, HVAC mechanic, someone installing a heat pump or
evaporative unit? And if so, were they anywhere near the leak area?
This question is important because people can often drop tools which
can penetrate the roof and cause a leak.
Q: Does it leak only when there’s a wind-driven
rain? Only when it snows?
A lot of times wind will drive rain up under overhangs where it can get
into the building where it normally couldn’t. Or if there is a turbine
vent that is frozen in place, the wind will drive the rain into it and
cause a leak. Snow is tricky because it can cause ice dams which will
allow water to back up under shingles, or it can be deep enough to go
over the tops of curbs. When it starts melting, it starts leaking.
Q: How long after precipitation starts does the
leaking begin? How long after the precipitation quits does the leak quit?
This will give the contractor an idea of how far the water has to
travel before it actually shows up.
Q: Has anyone been up in your attic recently?
A lot of times when plumbers, electricians, HVAC mechanics, etc. are
working in attics, they can knock a flashing loose, break a seam along a
condensation line, or even accidentally put a hole in the roof system by
puncturing it in the spaces between decking. None of this is
purposefully done, it’s just something that happens because attic spaces
are usually very cramped and difficult to work in.
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