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A lot of questions have been asked about how to locate a leak in a roof, but you can only locate a leak that you know exists, and the first noticeable sign that there is anything wrong might be drywall damage in your living space.

By this point, the drywall is obviously already damaged, and the roof decking or other behind-the-scenes parts of the house might also have significant damage, so you need to pay not only to repair the leak but to clean up the damage it caused.

If you knew about the leak when it first started, you might be able to repair the leak early enough that it wouldn't have time to damage anything else.

How can you monitor or screen for leaks or possible leak-causing damage in a residential roof, so that they can be fixed before they cause water damage?

interfect
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  • The problem is that a leak could, potentially, come in through any seam - e.g., typically 4'x8' plywood next to each other under the shingles, so you might have dozens of potential leak locations. Anywhere other than the actual source of the leak is likely to be so little water that it would be impossible to detect at a reasonable cost. Plus this leak detection system would itself require some serious installation work as it would need to have wires going all over the place. Plus roofs have a reasonable/known typical lifetime. My last leaky roof (hard to say now whether the cause was – manassehkatz-Moving 2 Codidact Aug 24 '22 at 14:04
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    It doesn't have to be an integrated electronic alert system; maybe there is a commonly recommended regimine of manual inspections of attic spaces, or somebody I should hire who flies over the roof every year with a drone? – interfect Aug 24 '22 at 14:06
  • bad materials or poor installation or other damage) lasted well over 10 years before any significant leaks. – manassehkatz-Moving 2 Codidact Aug 24 '22 at 14:06
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    If a shingle roof(quite common) you inspect and fix any damaged shingles as soon as possible. – crip659 Aug 24 '22 at 14:06
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    Looking from the outside is probably the most common thing to do. Inspection from inside the attic - for some that is easy, for some nearly impossible. – manassehkatz-Moving 2 Codidact Aug 24 '22 at 14:06
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    @crip659 How do you know that shingles need inspecting, though? Should you get up there and look after every storm? – interfect Aug 24 '22 at 14:08
  • Inside only helps to find leaking already there. It does not find minor damage to the top before leaks start. – crip659 Aug 24 '22 at 14:09
  • For shingles looking is the best, it finds ripped shingles, curling shingles, shingles that have the top protective covering wearing away. Quite a few roofs can look from the ground and see damage, binoculars can help see closer. – crip659 Aug 24 '22 at 14:14
  • I'd inspect after every serious storm (you'll have to define what's serious in your locale though). Doesn't take long, maybe 5-10 mins for a simple ground level eyeball inspection. If there's anything you can't see from the ground level or something seems off, add some time for ladder work. This applies to the interior as well (including attic), it's probably a good idea to do this again one or two days later to catch anything that took time seeping in. – MiG Aug 24 '22 at 14:35
  • The maintenance cycle for tiled roofs tends to be fairly long (depending on quality of course, but think 50 years), so it's more of a case of spotting tiles that have moved (therefore breaking the protective layer) or outright got damaged. Indoors, the attic's your main area to check, but also windows (and to a lesser extent, perimeter walls). – MiG Aug 24 '22 at 14:40
  • Not familiar with any systems that could detect leaks, as @manassehkatz-Moving2Codidact mentioned this might be costly if it does. I am however wondering now if it would be possible to utilise a few strategically located zigbee compatible leak detectors (the ones intended for washing machines and kitchens, how many and where depending on the structure of your house). – MiG Aug 24 '22 at 14:44
  • Keep in mind that thermal bridges and other forms of poor insulation also cause condensation indoors, so false alarms should be avoided (preferably by fixing the thermal bridges, which will also help your energy bill). – MiG Aug 24 '22 at 14:45
  • How about 4 webcams in the attic pointed at various directions that you can monitor on your laptop/phone/tablet? – LarryBud Aug 24 '22 at 14:47
  • You're better off to spend the money on building a better roof, less prone to leaking, than to spend money on monitoring a crappy roof for leaks. If your roof is crappy, or merely old beyond the typical life for a roof of its type, start planning and saving money to replace it before it leaks. – Ecnerwal Aug 24 '22 at 16:36
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    Sleep in the attic. – Hot Licks Aug 24 '22 at 21:33
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    Another source of attic moisture is unsealed/improperly sealed/cracked masonry. An architect tried being a general contractor and built our current home. Seems that no one sealed the chimney. Added caps, caulked the cracks and sealed the masonry. No more leaks there. – HABO Aug 25 '22 at 02:59
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    I discovered certain leak points when I was investigating why the woodpecker started hammering on the siding in certain points. Sure enough it knew there was moist wood inside even though there was no visual evidence of damage on the siding, but the roofing membrane had pulled away from the flashing in the upstream vicinity. – Ian W Aug 25 '22 at 04:45

5 Answers5

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I go up into my attic about once a month (or after we get a heavy storm) with a good flashlight and give everything a visual inspection. Specifically, I make sure I'm very accustomed to the way that the roof is supposed to look. Then, in the handful of cases where I've had a small leak, that leak stands out as pretty obvious.

Leaks generally start small and work their way up. When water first starts seeping in slowly, a lot of it gets absorbed by the wooden roof decking, the rafters, or if it drips down, by the wood on the attic floor. Wet wood is much darker than dry wood (insulation usually looks different as well), so I've always identified leaks by noticing the dark spot that wasn't normally there. If it's a leak, it'll usually be damp to the touch as well. You're technically not detecting the leak before it happens, but with regular inspections you can notice it before it has a chance to cause any real damage or make it through to the drywall. This is where it's important to know what your attic looks like under normal conditions, so you'll know that dark spot has always been there but that dark spot is new. Most leaks occur around places where there's already a hole in the roof (vents, chimneys, satellite dish mounts, etc.) so pay particular attention to those areas.

Again, it's not a perfect solution, but it's easy to do, free, only takes about 10 minutes, and is fairly effective.

bta
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    Of course, walking around on a roof could also lead to damage, eg: cracked shingles, or popped nails pushing through membranes, etc. (I know you are in the attic looking up, not on the roof). – Ian W Aug 25 '22 at 04:35
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    @IanW I don't see him suggest to get on the roof anywhere, but rather into the attic :) – MiG Aug 25 '22 at 05:01
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    @MiG, Noted in parenthesis, more of a general clarification to be careful. I know I damaged my roof by walking on it to inspect. – Ian W Aug 25 '22 at 05:49
  • You can do that as long there is enough hight for you to fit in. – Traveler Aug 26 '22 at 01:23
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Roof leaks are caused by many different things. For example:

  • Shingles or tiles: Cracked, broken, missing, worn
  • Flashing: Loose, broken, missing, poorly installed, worn
  • Gutters: misaligned, clogged
  • Ice dams
  • Flat roofs: insufficient or poorly spread gravel
  • All roofs: end of life

Most of these are difficult or impossible to detect directly. You need experience and expertise to be able to tell when normal wear leads to the need for spot repairs, total replacement, or when there are abnormal problems.

I know this isn't much of an answer but I think it's a really good question and unfortunately there isn't a magic answer. The best I have is: Read up on the particular kind of roof you have, know what KINDS of things can go wrong, understand that water travels, inspect it regularly so you are in tune with what "normal wear" looks like, and watch for stains or other signs of leaking. Have it professionally inspected once in a while, and learn from the person you hire to do that.

jay613
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  • It is not much of an answer, more a lecture. But people seem to like it. – Traveler Aug 24 '22 at 20:23
  • We had a ridge vent that let snow blow into the attic. Didn't know it until it started to melt and saw a wet spot on the ceiling. Went into the attic and started filling a bucket with snow and passing it down to the SWMBO who dumped it into a bathtub. When the tub was full she asked how much more there was. Sigh. – HABO Aug 25 '22 at 02:53
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    Most of these are difficult or impossible to detect directly amen to this... i've had roofs leak where I knew there was water coming in, a lot of it, but looking directly at the roof outside I had no clue how it was getting in. – Michael Aug 25 '22 at 03:03
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A visual inspection once a year or after a severe storm. A great pair of binoculars could save you trips to up on the roof. Look for any shingles that have lifted or are torn. Also look for nails that have started to come out, raised up from the singles, especially on the saddle shingles on the peaks. Once you detect flaws, fix them promptly. Unfortunately, most leaks are found by noticing a water stain on your ceiling. What you do then is put a pan in the attic over the spot to stop the water from soaking more into the ceiling and then start investigating where the water's coming from.

JACK
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Whether you have a tiled roof, a sloped one or a flat one, the roof’s surface can suffer from persistent moisture which leads to damage.

Many causes for leaks, and none is predictable but some are obvious like Shingles: missing, cracked, broken, Flashing: Loose, broken, poorly installed, worn, Gutters: misaligned, clogged.

The challenge is by the time you can see it, it has already progressed. The leak damage is not always directly under the problem, it might leak somewhere else .

You can detect any leak well ahead of time using a thermal camera, that professionals use.

From inside (under the roof),

Or without climbing on the roof from outside with drone.

Additionally it could expose roof insulation problems (hot spots).

Not only the roof: Infrared is helpful for all home insulation checking. On Hot days with AC running full blast it can detect your hot spots. On Cold winter days it can detect your leaks.

If you are looking for renting or buying: Some typical average costs are $250-350 for regular visual inspection, $550 for an infrared drone roof inspection. Slate and tile roofs are harder to inspect and it costs an average of $800 for large roofs.

DIY visual inspection: If you do it from under the roof, you can only reach about 1/3 of the area (where you fit in). If you do it from outside (walking on the roof), you must use safety line or risk you life.

Traveler
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  • Some large hardware store chains have tool rental services. Renting a thermal camera for an hour 2-3 times a year could be an even less expensive option. – bta Aug 25 '22 at 02:21
  • to be clear, you aren't talking about buying the camera when you mention ROI, right? – Michael Aug 25 '22 at 03:05
  • @Michael that is a individual choice, rent or buy. – Traveler Aug 25 '22 at 03:11
  • well I ask because I read it to mean "buy" until I got to "$550 for an infrared drone inspection" which makes it sound like you wouldn't be buying and probably not renting, but paying somebody else to check it with IR for you – Michael Aug 25 '22 at 23:14
  • @Michael the $550 was what you pay for drone inspection, it could be also great excuse to get a drone :) – Traveler Aug 26 '22 at 01:20
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Something I've learned the hard way is to get your roof inspected for the proper nailing pattern.

Nails should never fall in between butted shingles; I think they're supposed to be at least an inch from the butt but don't quote me on that.

MonkeyZeus
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