Help Save This School's Roof

Thanks for the good info. I need to do some more investigation. This is a large building with a flat roof and I am not sure what space is available for ventilating. You are right...this is a safety issue.

So, the water accumulation started after the hood/lights were installed, and you can't relate this to the weather? Is it rusty?

JaE seems to have it. Perhaps the path of JaE's condensation stream was interrupted by that new conduit used to install the hood? Or new J-box?

Just a thought.

i was told by a former employer that i am an expert at flat roof repair.

you can go on the roof after it rains and watch where the puddles go, or call me and i'll do it. . .

Simple information gathering is essential.

I know it sounds obvious, but, we have a leaking flat roof at work. The roofing people have been back several times. One day the maintenance company came in and removed lots of ceiling tiles, and, generally messed about for ages. When we eventually asked them what they were doing they said that they were looking for another source for the water (because all the attempts to fix the roof had failed). When we told them it only happened when it rained they went away feeling a little foolish.

As jerryalan says, go up on the roof after it's rained and watch the puddles.

Are you friends with anyone at the local fire department? Maybe you could schedule a "demonstration" for the students. The fire dept can pump plenty of high volume / low pressure water. They can mist over particular areas such as the HVAC and other mounted equipment. Or you could set up a lawn sprinkler and let it run through the day. That would provide plenty of time to allow for saturation of any insulation that it may have to pass through as well as isolating a particular area of the roof. This is assuming the leak only occurs when it is or has been raining. Otherwise I agree with JAE in that condensation could be the problem. The local grade school in Lawrenceville, IL. has a terrible problem with moisture in the building. When it was built a few years ago there where cut backs made to the HVAC system. This has resulted in many thousands of dollars to be spent on dehumidifiers and labor to control the mold that is growing in the building. It would have been cheaper in the long run to have put in the correctly sized system as recommended initially.

Perhaps the leak is really somewhere else on the roof and the cutting of the hole for the new hood simply allowed a new escape point?

The coincidence of the water accumulating and the installation of the hood speaks to me. It is most likely a curb flashing transition issue. Wait for the rain to fall, and do a rooftop inspection. I suspect you will find your problem area.

Second possible cause would be cold air intrusion back down the exhaust shaft causing condensation in a warm, humid kitchen area. Check for negative air pressure in the kitchen area. Do you have more than one exhaust fan that could cause the air to be pulled back down the hood?

I have a building that was built so poorly, that I cannot keep the outside air from between the floors. Talk about a humidity nightmare with outside air flowing between conditioned spaces. I am here to say to all mechanical types that 2 compressor units do not equal 2 stage compressor units! All or nothing! Cools like a fiend, but does nothing for dehumidification!

Like I said, check ponding on the roof after a rain to pinpoint possible avenues of intrusion, or check the possibility of condensation from a potential negative air situation. That's where I would start looking.

Good Luck,

Dave

Put a solution (which will mix with the water on the roof) and will show up under an Ultraviolet light source. After the next leak, if it comes from the roof, it will show up when illuminated withe the UV light. If it doesn't, you've got a problem like has been described in the previous posts about condensation.

I would have to agree with some of the other people. Just because the water build up near the new hood doesn't mean that's were the water is coming from. I would hazard to guess that the water has been leaking under the roofing tar for some time now and its only been since they put a hole in the roof that the water has found somewhere to escape. I would suggest going to the local hardware store and purchasing a can of Mastic (I think that's what it's called) which is a thick tar that doesn't harden and I would plaster a ton of it around any spouts or pipes or anything could could even remotely leave an opening for the water.

Your getting a lot of good information here. I'm a sheetmetal contractor and one of the things we do are kitchen hoods. Who is the hood manufacturer? Kees, Greenheck, Captiveair if it is some off brand then they may have not done as good a job with the electrical. Those lights, and conduit are sealed water tight on the interior of the hood. So the only place that the water can be entering is at the junction box on the top of the hood. If water is entering at the junction box then you should be able to tell and you would think that the other lights would have water in them as well if it was entering at the juntion box. You might look at the seal on the light that is filling up it might be getting in there. Is this a steam only hood, in other words do you do anything with grease? If you do and there isn't any grease in the light then you know it isn't a leak in the seals. You also might look at the water and see if there is any dirt or gravel that might come from the roof. That would tell you if it is a roof leak.

Has the system been air balanced? If you are worried about condensation then maybe the exhaust fan isn't pulling enough air, you might get a balancer out to look at it. Well good luck and I hope you find the problem.

We have used an infrared camera several times to find roof damage which was otherwise undetectable. Flat roofs have insulation beneath the rubber. If the roof leaks, the insulation gets wet, and it's ability to stop heat transfer is reduced. The bad area will look different (warmer in the winter, cooler in the summer) in infrared when compared to the remainder of the roof.

Your local electric company may have an IR camera they use for customer energy audits, or you may be able to rent one locally. If there is a technical or engineering college nearby, they may also have one you could borrow. Some larger roofing companies have also started using themto find problems.

I agree, I have found roof leaks with an IR camers before they have even caused staining or shown themselves to the naked eye. The IR scan from inside the room is so obvious when you see it, it is amazing. If it is done at night it will be a warm spot and if done during the day it will look cool. If you are on the roof at night, a word of advice, do not perform the scan while walking backwards. More than one person has been injured doing that. Also if the insulation is dry under the membrane you will probably have to spray water to induce the leak. Be prepared to find other leaks also, they tend to be like cock roaches. You never find just one cock roach, if you see one you have roaches.

Simple solution; the interior ceiling should be made of removable acusti ceiling tiles. Using a water hose let it run onto the roof for several minutes in the suspected leak area. Then remove one of the interior ceiling tiles and look for the leak. In some cases rust forms quickly between the lower roof and the inner ceiling crawl space, suspect that area first.

A. It may be in the area suspected, and judging by the newly installed apparatus it seems that more than one person was on the roof at any given time is a sure indicator that it is from the roof area. A nail that is not driven in properly, a screw without a rubber washer, a crack in the tar, a pucker at a seam or joint, are all formulas for a water leak.

B. condensation from the A.C. system.

C. Humidity/steam from cooking.

are what you should look for when assessing a roof leak.