Roof sheathing still moist after leak supposedly fixed

My condo had a new roof put on at the end of Sept. I found an active leak around Oct. 8 They did a repair around Oct 18th (just over 6 weeks ago) to the flashing of the powered roof vent. Problem is that some spots of the sheathing that were wet when it originally leaked have, at times, still been giving me excessive readings (as high as greater than 20% moisture content, highest reading) when I gently yet firmly touch the SURFACE of the wood with the prongs of the Moisture Detector.
I was suspecting it still has a slow leak, because moisture levels seemed to go up when it rained, but wanted to be 100% sure before I had the roofer rip up the roof to do another repair. I have been taking moisture readings, and wavering between thinking it's a leak versus just residual moisture being affected by changes in temperature and humidity. The wood was taking very long to dry out on it's own (sheathing faces the north) and I found that temperature did cause fluctuations (the meter gave higher readings when temperature got lower). I helped it dry with a hair dryer. I had gotten it to dry out to the point where I was consistently getting "dry" readings (under 14% at surface) when the outdoor temperature was 50 ish with humidity in the 40s.
It rained yesterday, and the moisture readings at the problem area went back to being as high as greater than 20%. Today (sunny and low 60s) the moisture detector is still (as of 12pm) giving readings in the 15 to 20% (or higher) range. I am sure that this would not be the case today if we did not get wet weather yesterday. As much as I'd like to give the roofer the benefit of the doubt, I am suspecting a slow leak.
QUESTION: Do I *definitely* still have a slow leak happening here? (or is possible that the reason for the higher readings is that residual moisture was still present and the wood only picked up extra moisture yesterday strictly due to relative humidity levels being higher). In other words, should I call the management company and insist I have a slow leak and have the roofer come and rip up the roof and do another repair?
Thanks,
J.
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imho, i wouldn't expect that the rh would affect the moisture content of wood that fast, so yes, i'd think you still have a leak.
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And it's NOT? condensation of warmer air onto the cooler inner surface of the roof? Just a vague thought!
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<<And it's NOT? condensation of warmer air onto the cooler inner surface of the roof? Just a vague thought! >>
Ok, but why would the condensation of warmer air cause just the wood in the problem area (area of the original leak) to jump up. Over time, (with help of a hair dryer) I had dried all the wood in this area to the point where I was consistently getting "dry" readings over the past week. Yesterday after it had rained much of the day, the readings went back up to the excessive level in just the area that had leaked before.
Given that it's only happening to the area that previously leaked, could it really be possible it's not an active leak?
J.
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Given that you cannot see any flowing water and you are monitoring moisture content of the wood, You may have trouble convincing those responsible to pay and work to do anything about it. They may however, have plenty of ready explanations, some of which may be correct.
At only more than 20%, you say that means it is wet but 20% doesn't sound all that high to me. What do you get when you float a scrap of wood in a bucket for a day then take it out, towel it off and read it. I just question your figure of merit for determining the leak (don't go by the instruction manual). An empirical experiment like that will help bring perspective to your number.
Condensation in an attic can be concentrated at any point that has more thermal mass than the average material around it. For example, if the powered fan has a heavy housing adjascent to the wood you are testing, after cooling overnight it will warm more slowly than the rest of the roof. While it is cooler than the surroundings and the humidity rises, condensation will collect in and on the wood of that area but not other nearby spots. This action is most prominant in the morning and if the day is warm enough, evidence is gone before long but if the weather is cool and damp, it may build up over days to weeks.
Try running the powered fan full time for a few days instead of on a timer/thermostat it is probably on now. This will prevent any condensation in the area and help eliminate that as a possibility.
When you get right down to it, you can simply wait for it to dry out then run a hose on the area for a while and look inside. A little food coloring may be too subtle to detect but something like that might be useful for tracking the water intrusion.
Its a tough call from here, let us know what the verdict is.
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<<Its a tough call from here, let us know what the verdict is. >>
Thanks, they agreed to try spraying a garden hose to try and detect the leak (with me in the attic).
I want to make sure the person on the roof with the hose does not go overboard though. When testing for a leak with a garden hose, is it important to NEVER EVER have the stream of water directed uproof (facing uphill) or would it still be fair to do this if one is careful to make sure the angle of the stream is kept to reasonable level (such as no lower than perpendicular to the line of the slope)? What do you think?
J
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