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Question DetailsAsked on 1/31/2014

I have water dripping from behind my stove hood. Lots of snow on my roof from heavy snow this winter. What to do?

My house was built in the early 60's and my stove has a cupboard over it where the vent runs up to the roof. I just found water dripping down my wall and onto the floor behind the oven. It is dripping very close to two electrical outlets so I am concerned about safety, mold, water damage, etc. the inside of the cupboard appears to be dry as is the outside of the vent and the fan undeneath the stove hood. We have had a lot of snow so far this winter and am not sure if the vent could be clogged with snow from my roof. I also am not sure who to call to fix this kind of thing but think it needs to be done right away. I have Home Service Plus through Centerpoint Energy but they won't go on my roof. Please help me!

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2 Answers


Call a roofer.

Identfy the source of the leak. Possible sources are:

- failed flashing

- seams in piping

- condensation

- entering behind the roof as a higher point and draining through at penetation location

Answered 6 years ago by WoWHomeSolutions


Take out the grease mesh filter screen so you can see up in there past the fan, with a LARGE flashlight (like a 6 Volt lantern or a bright trouble light), and look up in the duct - may be round about 6-10" pipe, or 4x10" or thereabouts rectangular. Usually a straight shot up to the roof about 2-3 feet above the ceiling to the roof cap. If yours has angled inlets on each side, may need a hand mirror to angle view up into the duct. If your stove is electric, unplug and pull it out so you can look up in the vent, if it is a straight shot up in the duct. Otherwise, if gas or can't pull out easily, use a mirror.

1) In daylight, look to see you are not seeing sky - if you are, you lost all or part of your vent hood.

2) If you see light shining in from one side along the duct but short of the roof, duct has separated. If light iscoming in at the top from the downhill side, then probably the flapper on your vent hood is stuck open, letting snow blow into the hood, which then melts and pools in the cap, eventually running down around the outside of the duct.

3) IF you see significant frost in the duct (assuming still cold outside and in attic) then you may have been running the fan for too short a time, so it melts some of the frost to water that dripped down, but did not run long enough to evaporate it. If your duct joints are configured so the upper pieces fit INSIDE the lower, meaning you will be looking up the the exposed bottom edges of each piece of duct, then the water will run down INSIDE the duct and come out at the fan, which evidently is not the case for you. If only happening in the recent extreme cold, than means you have a need for insulation around the duct, but you might get away with just running the fan for at about 30 minutes at least once daily to melt and evaporate the frost out. This frost is largely due to household air escaping up the vent 24 hours - most flappers do not really seal tight enough to stop this airflow.

4) IF above, but instead of seeing the bottom edge of the duct pices you see only the ends of the BOTTOM pieces sticking up in the next one, then frost melt coming down the ducts can get caught by and go through that seam, running down around the OUTSIDE of the duct into the cabinet. From your description, sounds like #3 is NOT the case, so could be this - frost melt coming down the duct till it hits the wall (and insulation there), pooling and running down wall.

5) Another possibility - leaking duct that formed ice around it from the moist air condensing and freezing (can build up several feet thick), which then melted when the outside air warmed up, coming down around the duct to the wall.

6) Another possibility is ice damming at or below the vent hood on the roof, backing meltwater up till it comes in under the flashing on the downhill side of the hood. Melting can occur due to the heavy snow cover - does not require outside thawing or rainy conditions, just the house heat on the underside of the sheathing can do that.

7) Obviously, a leaking flashing or rusted duct cap (especially on uphill side) could do this.

8) Unless you have a pretty much totally separated vent pipe so basically all the air is escaping into the attic, the snow will NOT plug off the vent - the snow lets enough air through that it will melt an airway in minutes flat with the fan running.

9) Another possibility you see a fair amount in cold areas is leaks from a vent or pipe penetration further up the roof, or underside frost melting, and running down the underside of the sheathing till it hits the cutout for the vent duct, then drips off or runs down the duct there. So, actual source ofthe water can be uphill of the palce it appears.

10) Your solution - from a do it your self standpoint: if you can get in the attic, or from a ladder get up to look in the eave in the rafter bay the exhaust fan duct goes up through, with a strong flashlight you may be able to see if you have a leak coming down from the roof, and should be able to see any icing and saturated duct insulation (if insulated). Obviously, if the underside of the roof is leaking or there is water tracking downhill on the underside of the sheathing, or there is icicling right around the duct where it penetrates the roof, then likely a leak at the roof - flashing, ice damming, etc. If you can get up on your roof, or reach that point with a snow rake from a deck or ground, you could clear the snow downhill from the vent hood and see if there is a large buildup of ice glaciering there which could be backing up water. You may be able to see from the ground - especially with binoculars or from a ladder without actually having to get up on the roof if that scares you, whether the hood has an ice blockage in front, or if the flapper in the opening is open when fan is not on. (Usually a gravity flapper that opens up when fan comes on, drops back roughly flat inthe opening when off). Looks like this typically - flapper may lay flat, or be inclined like this one

You may have trouble seeing if open or closed especially if it has bug screening over it, but if someone turns fan on and off, you can then see it move pretty easy in bright flashlight beam or good daylight.

Then you can decide if you want to attack the issue yourself or not - if you are not experienced with roof penetrations anything beyond melting an ice dam with hot water (from bottom uphill) and maybe patching any obvious flashing leak with asphaltic emulsion may be beyond you. Duct repairs, if due to a separated duct, are not tough - a couple of sheet metal screws with a power drill and water-resistant duct sealing tape.

11) From having contractor attack it standpoint: you need an HVAC contractor or roofer to find the source of the water and fix it - Search the List for local ones and their ratings. If you do not identify where the problem originates, I would go with a roofer because if it is a water on the roof issue he is best to seal that up right. He can also usually repair any broken or open jointed duct in the attic, whereas an HVAC contractor will commonly not get up on and fix roof cap leaks.

12) To temporarily protect the electrical and stove from water, you can use duct tape to make a diagonal trough on the wall to divert the flow to a tin can or bowl - run the tape diagonal down the wall at about 30 degree slope or steeper, sticking only the top half (longitudinally) to the wall. Every 6-12 inches, use a pice of tape fromthe bottom edge of the diagonal tape to the wall above it, to hold the tape in a curl, so it forms a rain gutter. Run tape into a water container at the bottom, that you checkk and empty as often as necessary. Don't leave on more than a week or so or it can pull your wallpaper or paint - and yes, you do risk some minor damage from the tape, especially on actual "paper" wallpaper.

Good Luck

Answered 6 years ago by LCD

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