Author Topic: Best way to find a leak  (Read 852 times)

neophyte

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Best way to find a leak
« on: April 30, 2018, 12:10:33 PM »
I have a 100 year old flat roof townhouse that is 3 stories in the front, 2 in the back. The ceiling below the area where the height changes has been leaking for a year now whenever we get really drenching rains with wind. It doesn't happen during average showers. I've had roofers out multiple times and had the roof replaced (well, I guess it needed to be done anyway). Still leaks.  Had the windows caulked, still leaks.  At this point, I suspect the windows or chimney. 

I cut a hole in my drywall at the leaky spot and I can see a wet joist about 2 feet away.  I'm thinking about spending the weekend taking a watering can out there and pouring it over one area, waiting 30 minutes to see if the ceiling drips, and then repeating in another area.   Is there a better way to go about this?

I'd love to insulate the ceiling above that room and patch up the drywall, but I want to make sure the problem is solved first.  Waiting months for a really drenching storm to come along only to find out the fix wasn't a fix is getting old.

phred

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Re: Best way to find a leak
« Reply #1 on: April 30, 2018, 12:34:19 PM »
A watering can is just not enough water; better to use a garden hose.

Leaks can travel several horizontal feet before appearing at your ceiling.  Since you had the entire roof redone this leak is a little puzzling.  Is there flashing including a cricket at the chimney?  Are the roof scupper holes unblocked so water can't back up? Anything else poking up thru the roof. 

Best would be to be up there just as the rainstorm ended.  Pools of water means there is no leak at that spot (else the water wouldn't pool).  Where there is no standing water is probably an entry for the water. 

Fishindude

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Re: Best way to find a leak
« Reply #2 on: April 30, 2018, 12:35:32 PM »
You must not have used a very good roofer if they replaced everything and it still leaks?

A competent roofer or good general contractor should be able to figure it out for you relatively easily.   Now, they might need to try 2-3 different things before they get it solved, but a competent individual should be able to handle it.   Hard telling what it is without seeing things first hand, but it could be the roof, the wall, windows, flashing, penetrations, etc.

lthenderson

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Re: Best way to find a leak
« Reply #3 on: May 01, 2018, 09:35:08 AM »
Leaks, especially the intermittent kind, are very hard to locate. Water can run sideways for quite a distance thanks to surface tension and then dry up later making it impossible to track. If you have access to the spot in the ceiling, you may want to try dusting the area with something like flour so that it leaves a trail behind after it has dried up to help get you further up the path of where it is coming in. Windows and chimneys are both good sources that can let water in if not properly flashed and from the outside you are none the wiser. I once had a leak that started in bad flashing around a chimney, traveled a few feet underneath the roofing shingles before coming in a gap in the roof decking, from there traveled about two feet down slope to a vent pipe going up through the roof and then down and over a few feet to the basement bathroom ceiling where it finally manifested as a stain beneath a p trap in the plumbing.  With water pipe in the ceiling of the downstairs bathroom due to a bathroom above and over a dozen horizontal feet at the crow flies between the stain and where the chimney stands, it was a real doosy to figure out.