Leak Chasing 101
Finding the leak is half the battle. Roof leaks
are usually not difficult to repair… But finding them
can be tricky. The main problem is: The place the
leak is showing up inside, may not be directly
under where it’s coming in outside.
For example, on a sloped roof, the water might get
under the roofing at a protruding nail, and then run
between the roofing and the plywood deck until it
gets to a seam in the plywood. Then it drips onto
the top side of a cathedral ceiling where it runs
down to a seam in the drywall. The spot it’s getting
through the roofing can easily be several feet away
from the spot it’s showing up inside.
Drips can also get diverted by rafters and stuff they
land on in the attic. I chased one leak that rode an
air conditioning duct for twenty feet from the spot it
came in.
Analyzing leak signs in the house. The first
step in finding a leak is to check out where it is
showing up in the house (assuming it’s not just
leaking outside through a soffit).
What you see inside can tell you a lot. It can tell
you if you’re looking for a big leak, or a small one.
A tiny stain on the ceiling indicates one thing. A big
hunk of drywall lying on the floor indicates a lot
more water coming in.
If the stain is still wet, you know it’s an active leak.
If not, it might be from an old roof repair, but the
ceiling was never fixed. Or perhaps the old stain is
bleeding through the new paint.
The most important thing you learn is EXACTLY
where it is showing up inside the house. The roof
problem may not be directly over the spot, but
that’s the best place to start looking. Here’s how to
transfer the location from inside the room to the
roof.
• Measure the exact distance from the leak to a
"reference point" you can see both inside and
outside the house. Windows and exterior doors
make great reference points. Draw a little sketch,
showing the distance between the leak and your
reference point
• When you are back outside, place your ladder
right by the reference point, IF that’s a safe place
for it. (See the section in Chapter Seven on ladder
safety) If that’s not a good spot for your ladder, just
toss a little pebble on the roof directly over the
reference point, to get you orientated up on the
roof.
• Note the width of the soffit overhang on your
sketch.
• Also, remember that your measurements
inside the room are horizontal and the ones on the
roof will be along a sloped plane (unless the roof is
flat). You need to allow a little for this difference.
On a roof with a 5:12 slope, add 8.3% to the
horizontal measurement. That comes out to an
extra foot along the slope for every 12 feet
horizontally. Add a little more for steeper slopes, a
little less for those with a lower slope.
This may allow you to find the roof problem without
ever going in the attic. That is especially helpful
when you have little or no attic access. It is also
helpful when you are not athletic enough to crawl
around attics. That’s a condition I found myself in
recently while recovering from some broken
bones.
Finding leaks without going in the attic can be a
little more challenging, but entirely doable. Like
most things, it gets easier with experience. www.macgregorroofing.com
Following the water path through the attic. Still,
finding a roof leak is somewhat simplified if you
have good attic access… and you’re up to the
task. You can see where the water is dripping
through the roof sheathing and if it is being
diverted. This is how to proceed…
• Gather up a flashlight, a bucket, a tape
measure, a hammer, a couple long nails, a short
board (two to three feet will do), writing paper and
a pencil or permanent marker.
• Go on up in the attic but watch where you step
(or crawl). You could easily break through the
ceiling. KEEP YOUR WEIGHT ON THE
FRAMING!
• Get directly over the wet spot. A helper can tap
on the ceiling with a broom handle if you're not
sure of the location.
• If the water is still dripping, get the bucket
under it. It’s better to catch the water in the attic
before it soaks into the insulation and ceiling. Set
the pail on your board, spanning two ceiling joists.
Don't set it right on the ceiling because the drywall
might not take the weight as the bucket fills up.
• Mark the spot on the underside of the roof
sheathing where the water is coming through.
• If the water has already stopped dripping, pull
the insulation back and set your flashlight on the
stain pointed straight up. Look for water marks on
the wood and mark the spot where they first show
up.
• Look for a reference point you can use when
you are up on the roof. This might be a plumbing
vent pipe going through the roof, a “goose-neck”
vent, a skylight or a chimney.
Measure from your reference point to the spot
where you first see the water coming through the
wood sheathing. This may not be the exact spot of
the actual leak, but it’s where to start looking when
you are up on the roof. Make a little sketch to keep
yourself orientated.
• If there are no good reference points to use,
you can make your own. After the rain has stopped
and you're ready to make the repair, go ahead and
drive a nail up through the roof at the exact spot
the water was coming through.
You might be reluctant to put a hole in your roof,
but this can be the best way to pinpoint a leak.
Using this method, I have found hidden leaks that
stumped other roofers.
Just don’t forget to patch the nail hole!
Pinpointing the problem on the roof. Using the
detective work you’ve done so far, you should be
able to get on the roof directly over the leak… or at
least where it's showing up inside. Now you need
to be very observant.
Starting at the spot you've pinpointed, do a very
thorough search of the area, particularly the
"uphill" side of the leak. You are looking for any
place at all where water could get through the
roofing.
Sometimes the problem is obvious, sometimes it’s
hidden. Keep looking. Be patient. The water has to
be getting in someplace.
Water-testing tips. Flooding the area with a water
hose MIGHT help you pinpoint the problem.
One big caution here; avoid walking on a wet
roof… especially if it is wood, tile or metal. Keep
your ladder off to the side -- away from the water
Start low at first. By that I mean, direct the water to
the lower parts of the roof. Let the water run on
each area for about fifteen minutes, before
directing the stream to a higher spot.
If there is a flashing detail in the area such as a
vent, plumbing pipe or valley, it might very well be
the problem. Directing water right on it will quickly
reveal if that’s the source of your leak.
It’s easier and safer to have a helper in the house
(or attic) monitoring the leak area while you are
water testing. Other wise, you will have to keep
running up and down the ladder.
Cell phones work good for coordinating your
efforts. Just don’t lose your phone in the attic
insulation. Yep, I’ve done that too!
After the repair, water-testing the same area
MIGHT tell you how effective your work was.
Just remember that water testing isn’t always
definitive. It’s tough to duplicate a torrential
blowing rain with a water hose. But if it still leaks www.macgregorroofing.com
when you water test it after the repair; you know
you still have a problem.
Six “head-scratchers” that might trick you. I
hate to throw technical jargon at you, but nothing
fits like the term us roofers use to describe a leak
that’s tough to find. We call it a “head-scratcher.”
An especially puzzling one is called a “REAL headscratcher.”
Back when I “knew it all” I would get irritated when
I couldn’t instantly find a roof leak. There’s a fine
line between confidence and arrogance… I
confess to having strayed over the border on
occasion. But as I’ve gotten a little older, I’ve
become more philosophical on the matter. I’m now
convinced that the very purpose of a “headscratcher” is to keep me humble!
Another thing I’ve learned over the years is that
leaks aren’t always caused by roof problems. Here
are some of the other things it might be:
1. Plumbing pipes. Leaks in water supply lines
can show up even when it's not raining. Typically,
a joint is dripping or there’s a little spray of water
coming out a pinhole in a pipe. Drain lines can also
leak. You find those under roof drains, plumbing
fixtures and hot tubs.
2. Air conditioners. Clogged condensate lines
are the main culprits.
I lost a 4’ x 4’ piece of the ceiling over my
daughter’s bedroom from this very thing. My wife,
Martha, saw the bulging drywall and thought it was
a bad roof leak. She told me I better come quickly
because it was going to collapse. But… I was
watching a good football game at the time. I
glanced out the window at the sunny day with no
rain in site, and told her I would get to it at half
time. About two minutes later I heard the crash
and she hasn’t let me forget it ever since. Some
day I’ll learn to LISTEN to that woman!
Another common leak problem with air
conditioners occur when the drip pan under the
condenser rusts out. One time I asked an AC tech
why they weren’t made from aluminum. He just
grinned and said “Why do you think?”
3. Windows and siding. These leaks show up
with torrential rains combined with strong winds.
4. Stucco cracks. Even small cracks suck water
like a sponge. The horizontal cracks are the worse.
And your sprinkler system might be supplying the
water when it’s not raining.
5. Chimney leaks. Leaky mortar joints might be
the problem. Or it might be an ill-fitting chimney
cap that is letting water in.
6. Planters. Some times these are mounted on
an exterior wall and leak inside, but it has nothing
to do with the roof .
macgregorroofing.com
