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These stories tell of situations found by home owners and moisture investigators in cold climate houses.

#1 - The Wet Attic in Winter

#2 - Small leak leads to a Big mess

#3 - Little Leak = Big Mystery

#4 - Leak Seeker

#5 - Experience 

#6 - The Unseen Drip

#1 The Wet Attic in Winter

A distressed homeowner called us on a Friday afternoon in late January with a frantic story of water dripping through a bedroom ceiling light fixture and a wet stain at the corner of the bedroom ceiling. The customer stated they had a new furnace, water heater and central humidifier installed earlier that month. The customer stated they had looked in the attic and found everything wet. They had contacted the furnace installer who sent out a representative to look into the attic. The installer’s representative recommended the attic be examined for air leaks from the house into the attic. (Attic Bypasses) We recommended the humidifier be turned off however the customer said they had already done that.

Given the conditions and events described over the phone, we recommended the attic be examined as soon as possible and scheduled our appointment for the next morning. Upon arrival, I examined the new furnace, water heater, and humidifier. I found nothing unusual in these appliances and moved on to the attic access. In order to enter the attic it was necessary to remove wire shelving and clothes racks. As soon as my eyes were above the attic hatch, I could easily see the plywood was very wet and portions were frosted along the north eave.

         (C) 2009 Wet plywood in attic in winter, due to condensation.  Photo by Roger Hankey, ASHI Certified Inspector, Winter Park, CO

Given the extremely high humidity and the very damp plywood, we obtained several fans from the homeowner and set these up in the attic, to begin to dry the attic by forced ventilation. After the fans were set up and running, I began a further examination of the attic. Within a few minutes, I discovered the furnace vent, a double wall metal “B” vent, which looked like it might be disconnected at the first joint above the ceiling.

     (C) 2009  Disconnected furnace "B" vent in attic.  Photo by Roger Hankey, ASHI Certified Inspector, Eden Praiarie, CO

I moved into position to closely examine the vent, removed some insulation from around the vent and discovered that not only was it disconnected and offset, but the ends of the “B” vent were damaged and someone had made one or more make-shift attempts to reconnect the pipe using only metal foil duct tape.

I repositioned the vent and re-taped it together. I showed the home owner the photos of the vent and began asking questions about the house. The homeowner recalled that the house had been re-roofed (including tear-off of old roofing) a few years ago. The owner also stated that the representative from the heating firm that checked the attic two days earlier had viewed the attic only from a ladder.

My written report concluded that the primary source of the excessive water in the attic was from condensation from the water vapor found in the gas furnace and gas water heater combustion byproducts where were venting into the attic. This water vapor had condensed on the plywood due to extremely cold weather (below zero) in the several days prior to our inspection. We recommended that the owner have the heating contractor repair or replace the vent immediately at no cost to the customer, since the heating firm had failed to determine the integrity of the vent when installing the new equipment less than 30 days prior to this event.

          (C) 2009  Disconnected furnace "B" vent in attic.  Photo by Roger Hankey, ASHI Certified Inspector, Eden Praiarie, CO

This case provides a critical reminder for homeowners and inspectors. If extremely high moisture conditions exist indoors during winter, the inspector and/or homeowner must look FIRST for combustion venting problems, as gas heating equipment produces large quantities of water vapor during operation, and when operating frequently in extremely cold weather, the quantity of water vapor produced will create excessive condensation on any cold surface exposed to the vapor. Venting combustion products is essential to remove this water vapor and carbon dioxide, since being heavier than air, the carbon dioxide can accumulate near the burner and displace air needed for proper combustion. Blocked or disconnected vents can lead to the production of carbon monoxide if insufficient air reaches the burner. Occupants exposed to these high moisture conditions should be moved to fresh air and advised to seek medical attention for possible carbon monoxide poisoning.      Published in the ASHI Reporter June 2009.

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#2 - Small leak leads to a Big mess

Another late January case started with a customer calling in the evening to report a ceiling stain and asking for a moisture investigation as soon as possible. We had done a full home inspection on this house for this customer a year and a half earlier. Our original report listed some stains on the vinyl siding but did not reach any conclusions since the attic could not be opened during the original inspection.


Upon arrival a day and a half after their call, the customer explained that the interior ceiling stain had turned into a leak, and that he had found and repaired the leak, but that the stains on the vinyl siding had become extremely prominent, much more so than during the original inspection. He further explained that the leak was at a water supply valve in the bathroom vanity sink cabinet. He showed me the valve and I confirmed that the valve was no longer leaking.       Leaky water supply valve to bathroom basin (C) 2010


While laying on the floor to examine the valve, I happened to see that the air supply register in the toe space of the vanity cabinet was backed with a strip of foam. The customer stated that his wife had installed the foam to serve as an air filter. I removed the register grill to reveal that the supply air duct did not make a direct connection to the register. Rather, it delivered air to the entire bottom of the vanity cabinet.

   Air supply register removed below bathroom basin (C) 2010


A closer look into the cabinet showed that the water supply pipes descend through the bottom of the cabinet and into the joist space between the sub-floor and main level ceiling.


    Air supply duct below bathroom basin cabinet (C) 2010


The water stains both interior and exterior were below the bathroom on the same side of the house.    Water stained vinyl siding (C) 2010


Given that the bathroom was on the exterior wall, I asked if the basement was still unfinished. It was and I found the rim joist insulation was unfaced fiberglass batts with no interior vapor retarder or air barrier. Also the joists were manufactured “I” joists with provision for quick wiring knockout openings in the web of the joists.     Stained rim OSB behind exposed fiberglass (C) 2010 Photo by Roger Hankey, ASHI Certified Inspector in Winter Park, CO

Given these conditions, and the pattern of the exterior stains, I concluded that the leaky valve created a high moisture condition in the cavity between the floor joist space below the bathroom. Further, the poorly detailed air duct with its partly obstructed register and pressurized the joist space with hot air. Finally, I theorized that this warm humid air passed through unfaced fiberglass insulation in the rim of the second floor at least in the joist space containing the leaking pipe, and probably into adjoining spaces via holes in the joists. This moisture condensed in the wall sheathing and bled through to the siding.


I recommended the filter foam material be removed from the air grill, and that the air duct be modified so that warm air did not pressurize in the bottom of the vanity cabinet.

The customer has not reported any further leaks or staining incidents. The lesson from this mystery is that moisture will migrate from areas of high air pressure and high vapor pressure to areas of low pressure and low vapor pressure at all locations that do not have an effective air barrier and vapor retarder. While it was accepted practice in 1998 to install rim insulation without a vapor retarder, the laws of physics apply equally in the rim as they do in any other wall cavity. Today, Minnesota builders are required to properly detail a vapor retarder and air barrier on all areas of the building envelope.  Published in the ASHI Reporter July 2009.

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#3 - Little Leak = Big Mystery

A customer called in early October with a challenging moisture problem. He said they had a wet spot on the main floor ceiling of their two story house. They were the original owners of this 8 year old home and had seen this wet spot develop on two other occasions.


The master bathroom was above the area where the ceiling was damp, but a test of all the plumbing fixtures did not worsen the damp spot. I opened the access panel at the faucet end of the bathtub and saw no evidence of leaks at the water supply or drains. The shower stall was ceramic tile, but I found no evidence or missing grout, loose tiles, or poorly caulked joints at the shower door.


Rather than give up, I inquired further about when the damp spot appeared. The customer wasn’t certain, but the current condition had developed within the previous two days, both of which were rainy, including the day before which included a cold windy day-long drizzle.


I decided to examine the attic since it had begun to rain again a little. The main plumbing vent stack was visible from the attic hatch. When I shined my light on the pipe a few drops of water were visible on the exterior of the white PVC vent pipe. I cleared away some of the loose fiberglass insulation around the pipe at the second floor ceiling. Sure enough, there was damp wood at the top of the frame wall partition which contained the vent pipe.


     (C) 2010 Plumbing vent with rain water leak into attic Photo by Roger Hankey ASHI Inspector in Winter Park, CO


Looking up the pipe, I saw a tiny spot of daylight at the neoprene collar which served as the flashing for the pipe’s roof penetration. The pipe had streaks of water along its full length.


     (C) 2010  Small leak at neoprene flashing around plumbing vent.  Photo by Roger Hankey, ASHI Certified Inspector Winter Park, CO


Looking again at the point where the pipe penetrated the ceiling, I saw that the pipe penetration was not sealed with foam and that the pipe descended into the wall cavity. I returned to the master bathroom and determined that the pipe was located in the wall behind the toilet. I took a few measurements and made similar measurement in the main floor. The wet spot on the ceiling aligned directly with the pipe, which made a turn from vertical to horizontal in the joist space between the ceiling and the floor above. Therefore, the water from the flashing leak at the plumbing vent traveled down the vent pipe, through the attic, down the bathroom wall cavity, and into the floor joist space before it dripped off the pipe elbow and onto the ceiling. This only happened when the wind blew in a certain direction, and the pipe received rain continuously for an extended period of time.

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#4 Leak Seeker

My basement carpet is damp and smells moldy”. This call sounded like a typical wet basement investigation and began with a typical examination of the wet area. The room with the odor and damp carpet was actually a wood paneled 8 ft by 8 ft room in the basement. The room was used as a large clothes closet and had numerous metal storage racks for garments and shoes.

I knelt to lift the corner of the carpet, and quickly arose with wet knees. The moldy odor was strong and I quickly determined that a large area of the carpet was wet. I asked how long the customer had noticed any dampness or odor. They said the odor had been getting worse over the past few weeks but they only recently noticed the dampness.

I recommended immediate removal of the carpet and pad and offered to aid in moving the racks and removing the smelly carpet and soggy pad.

       (C) 2011 Wet carpet in basement closet. Photo by Roger Hankey ASHI Certified Inspector in Winter Park, CO

The basement was small and filled with many other stored items, but no other area of the basement had any evidence of dampness. Once the racks, carpet and pad were out of the way, I began to look for the source of the water. There was a partly clogged rain gutter on the porch adjoining the same side of the house as this wet closet, but the grade slope and drainage were appropriate and I found no sign of dampness around the basement window in the closet. A close look at the baseboard in the closet helped me direct the focus of the search.

       (C) 2011 Stained baseboard in damp closet. Photo by Roger Hankey, ASHI Certified Inspector in Winter Park, CO

The black stain on the baseboard was highest directly below the drain cleanout plug shown in photo 2. There was no stain on the wood paneling at the cleanout, but I quickly determined that this was probably the kitchen sink drain. I had the customer place the stopper in the sink and fill the basin full. Upon my signal, the customer released the water into the drain, and within a few seconds a small amount of water appeared on the basement floor next to the wall. The water flowed from behind the paneling and onto the floor directly below the cleanout. This confirmed the source of the leak, which the customer now realized had been a chronic problem. I recommended the customer have the drain repaired by a qualified plumber.

This was not the first time I’d found the cause of a wet basement to be a damaged leaking drain. An earlier case was equally frustrating in lack of clues. The home owner had already cut out part of the gypsum wallboard in his recently finished basement in an attempt to find the leak.

         (C) 2011 Wall opened to reveal drain pipe.  Photo by Roger Hankey, ASHI Certified Inspector in Winter Park, CO

I found no exterior conditions that could contribute to a wet basement and had the owner conduct a kitchen sink drain test with a full basin of water. The test revealed a small leak in the sink drain caused when the cable tv installer drilled a stud alongside the kitchen sink drain and his drill just penetrated the inside of the pipe.

        (C) 2011 Drain pipe with hole from electrician. Photo by Roger Hankey, ASHI Certified Inspector in Winter Park, CO

The pipe was repaired with ABS joint cement and restored to use. The lesson from these cases is that when the typical exterior causes of wet basements are not found; remember to check for slight plumbing leaks. This type of leak may not appear if water is simply allowed to run from a faucet into the drain. Draining a fixture full of water helps provide a surge of water more likely to reveal the leak.

                                         The Unseen Drip

This case, like many others, begins with a small amount of occasional dampness or drips in a ceiling with small amounts of water damage.   T
he homeowner - customer was asked to describe the history of the leak including as many details as possible about when the leak occurred. 

The homeowner stated he bought and occupied this older remodeled home around April 2011 and has had chronic slight water seepage during the past three winters in the wall and ceiling below the master bathroom. He removed portions of the wall and ceiling to reveal the subfloor and water supply pipes to the hand wash basin located above the water damaged area. He stated that the water entering the subfloor is slight, always in the same location, and occurs only in cold weather. The homeowner was unable to find a source for this occasional leak.

Using the copper hot water supply tube and a warm air supply duct as reference points, the main wet spot was found to be slightly left of the hot water supply to the left hand sink basin. No water supply tube leaks were found, and while the PVC trap and drain were properly configured, the joints lacked purple primer.     This is not consistent with a best practice installation, but no leaks were found in the drain, even when draining a basin full of water.

(C) 2015  Minor water damage in subfloor beneath a remodeled bathroom.  Photo by Roger Hankey, ASHI Certified Inspector, Winter Park, CO


 (C) 2015  PVC trap connections in a remodeled bathroom.  Photo by Roger Hankey, ASHI Certified Inspector, Winter Park, CO  (C) 2015  Hand sink base cabinet in a remodeled bathroom.  Photo by Roger Hankey, ASHI Certified Inspector, Winter Park, CO


When looking below the hand sink cabinet, we noticed a hole in the back of cabinet at the upper left. A PVC pipe was visible through the hole.  A close view of this pipe revealed a joint with a water drip on the joint. This joint was also not treated with the pvc primer. The dripping joint is aligned vertically with the water damage in the floor below.  We wiped the water off the joint and went on to seek a cause for the drip.      (C) 2015  Drip at PVC vent joint behind a hand sink base cabinet in a remodeled bathroom.  Photo by Roger Hankey, ASHI Certified Inspector, Winter Park, CO

The owners original statement that the leak - drip only forms during cold weather led us to examine the attic.  Frost had formed on most of the roof sheathing on this cold morning. We also saw several pvc plumbing vents running above the insulation, and areas where insulation was compressed, displaced, and not covering the vent pipes close to the ceiling.


 (C) 2015  Frost on roof boards in the attic of a remodeled older home.  Photo by Roger Hankey, ASHI Certified Inspector, Winter Park, CO  (C) 2015  Exposed plumbing vents and displaced - compressed insulation in the attic of a remodeled older home.  Photo by Roger Hankey, ASHI Certified Inspector, Winter Park, CO
The frost, exposed vent pipes, and the compressed - displaced insulation were the final clues needed to reach the following conclusion:  a large volume of warm water vapor rises in the plumbing vents when the shower is used.  When the attic is very cold, some of this water vapor condenses in the vent which is pitched to flow back toward the drain.  Condensate flowing back down the vent reaches the poorly cemented joint in the vent behind the hand sink cabinet.  This was confirmed when a second drip formed at this joint about a half hour after wiping away the first drip found. 


The recommended corrections were to have a plumber correct the leaky joint behind the hand sink base cabinet, and to improve the attic insulation including attempting to stop warm air leaks into the attic. (The source of the moisture creating the frosted roof boards.).

This moisture mystery serves as a reminder that a pressure test of the drain, waste, and vent piping is recommended after any additions or alterations are made to the plumbing system.  All joints in the system must be tight, since a loose joint in the vent can permit sewer gas to enter indoor air, as well as cause an occasional condensate leak.        

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