Indoor Swimming Pool Roof

Northdale Rd, Toronto, Ontario
Job Sold: 
May 2010
Job Completed: 
July 2010
House Age: 
20 Years
Roof Age: 
1 Year

Located on the south side of Northdale Rd facing north. The structure is a two-story detached wood frame brick, stone veneer and Stucco. The affect portion of the structure consists of a single story enclosed room containing an inground pool, hot tub, washroom, shower area, sauna room, and a utility room with the pool pump and heater.


Click here to download PDF of Indoor Swimming Pool Roof Case Study.

Roof Type: 

The roof structure consists of a hip and ridge with an adjoining flat roof. The roofing materials consist of Asphalt Laminated Shingles with Attached Modified Bitumen Flat. Aluminum Soffit Fascia and Eavestroughing surrounding the compete roof.

Reason Homeowner Called: 

The Homeowner started investigating the problem with the Indoor swimming pool because of water damage in the ceilings, exterior walls, and exterior walls. The leaks first showed up on the exterior walls from the roof over the indoor pool. The homeowner also identified ice accumulation on the roof and the eaves. The swimming pool roof is attached to the back of the home proving a visual for the Homeowner from the second floor. The homeowner could see the ice build up on the roof and figured it was the problem. Homeowner also noted the roof had icicles at hanging from the eaves.


It was reported by the Homeowner that they first contacted their insurance company. The ensure contacted an Engineering firm and determined that “the moisture and condensation conditions is like the result of a number of contributing factors.

  1. A lack of ventilation in the attic area due to blocked perimeter soffit venting,
  2. Heat Loss from the mechanical heating ducts penetrating the ceiling,
  3. Lack of and poorly wrapped insulation on the mechanical truck and shoots running through the attic,
  4. Breached air and vapour barrier allowing moist air to penetrate the attic,
  5. Inadequate mechanical dehumidification equipment in the pool area. The Homeowner was informed by the insurer that they were not covered for this loss.

Juffs Roofing was contacted by the Homeowner In February 2009 along with consulted 4 other roofing contractors. Only one other contractor identified the problem, none of the other contracts came up with the proper solutions. All 4 of the contractors said they need a new roof, and one said they needed more venting and new plywood, but unfortunately no one identified the source of the problem or a solution on how to properly correct it.


Exterior Roof Picture


Exterior Roof Picture


Investigation and Inspection: 



  • The shingles were replaced by the previous owner a little over a year ago. Unfortunately no effort was made to correct the problem. Shingles were in good condition.
  • Modified bitumen flat roof system over part of the roof tied into the exiting shingle roof.
  • Ice damming at the eaves edges. Moisture stains on the exterior stucco below.
  • Continues ridge vents with no external baffle and perforated soffit panels with minimal or under vented intake Net Free Ventilation.

Interior:  We were able to confirm the following

  • Dark stains on the underside of the plywood roof sheathing. Noted possible mould in the plywood.
  • Heating and Air conditioning trunk and shoots running through the attic with R-6 foil backed insulation poorly rapped and insulated.
  • The attic was installed with fiberglass batts of insulation mostly blocking the soffit ventilation.
  • Tongue and Grove Cedar Ceiling with several registers installed through the ceiling most likely leaking the conditioned air from the pool area into the attic.
  • Poorly sealed attic hatch leading from the ceiling of the pool area.
  • Chimney Vents penetrating through into the attic.
  • Obvious moisture stains at the perimeter of the ceilings and walls located on all side of the building.

Result of the initial investigation

We have solved similar situations in many homes where moisture and condensation issues have created similar problems. Because this was an indoor swimming pool we wanted to make sure were 100 percent with our recommendation. To confirm our understanding of the problem we decided to revisit the home a conduct thermal imaging. The following explains the advantages of thermal imaging and a few of the pictures included to show the results.


Thermography date: March 12, 2009

Outdoor temperature: -2 °C       

Indoor temperature: 22.2 °C

Temp diff In-Out (t: 20.2 °C      

Weather: Cloudy

Equipment: Flir B400/Tramex Moisture Meter



Infrared (thermal) imaging is a technology that shows you aspects of a building that can’t be shown using conventional inspection methods. Thermal imaging produces images of invisible heat energy emitted from objects and systems in the building and allows us to measure it.


Thermography is a "heat diagram" or a visible picture using the infrared spectrum. This imaging technique is a powerful and non-invasive means of monitoring and diagnosing the condition of buildings. Thermal imaging inspections can provide immediate documentation of as-built and post restoration conditions, post-damaged material assessment, energy inefficiency problems.


Typically, moisture on building materials will evaporate and cool by as much as 3.89 °C. A wet spot (when observed with an IR camera) is clearly visible as a distinct cool spot. Thermal imaging helps to diagnose the problem rather than merely identifying symptoms and can sometimes, but not always, identify and document: missing, damaged, and/or wet insulation; heat loss and air infiltration in walls, ceilings, floors, windows and doors; water and moisture intrusion that could lead to mold; possible pest infestation; hidden roof leaks before they cause serious damage; air conditioner compressor leaks; under fastening and/or missing framing members; structural defects; broken seals in double pane windows; energy loss and efficiency; dangerous flue leaks; damaged and/or malfunctioning radiant heating systems; unknown plumbing leaks. These images can then be included in your infrared inspection report, providing supporting documentation to the report. A picture is always worth a thousand words. 


Thermal Imaging


Captured at: West Facing Wall and Ceiling

Moisture Intrusion

Comment:  Area indicated by marker (Mk) showing signs of moisture intrusion coming in from the top of wall and travelling across the cedar under finish and ceiling joists.


Recommendation:  Investigate further. Results are consistent with moisture and condensation in attic above indoor pool.


Captured at: Indoor pool - right side facing house

Water Intrusion Pattern

Comment:  Image showing signs of moisture intrusion coming in from the top of wall and travelling across the cedar under finish and ceiling joists. This water intrusion pattern is underneath the area on the flat roof that is holding water and the dried area that retains the rooftop water.


Recommendation:  Investigate the flat roof and pool roof connection area.

Captured at: Register at back of indoor pool

Registers in indoor pool room

Comment:  Registers in indoor pool room are showing signs of heat loss through register and duct work.


Recommendation:  Investigate further. Additional heat being pushed up to attic will help in creating moisture and condensation in the attic. Anywhere you have hot air meeting cold, or cool, air you will get condensation buildup, which in turn creates the moisture and condensation.


Captured at: Flat roof, image taken from balcony

Flat roof retaining surface water

Comment:  Marker showing area on flat roof that is retaining surface water and pooling. The two areas are showing where the roofing membrane has moisture intrusion.


Recommendation:  Investigate the roofing membrane and possibly take a core sample.


Cause of Problem


The thermal imaging confirmed the following problems:

  • Moisture generated by the pool was entering the attic through the bye passes (openings) created by the mechanical system and light fixtures and cedar tongue and grove ceiling.
  • During the winter months when the roof deck temperature becomes cold, the warm moist air from the pool causes condensation on the underside of the roof deck. The moisture was so intense it disguised it’s self as a roof leak, creating what appeared as a roof leak.
  • The imaging also confirmed some minor issues with the flat and drainage.


  • Close off all by-pass from the attic.

  • Removal of the roofing materials and plywood roof deck to gain access to the damaged insulation.

  • Expose all rafters and treat with mould killer.

  • Spray foam the entire attic floor and all mechanical system with 2lb foam. 2lb foam provides almost double the r value per inch. By its nature it acts as a vapour barrier and air barrier. This will prevent conditioned air from the pool air and the mechanical trunk, shoots and registers leaking into the attic.

  • Remove soffit and install vented soffit panels with the required intake ventilation to meet the asphalt roofing manufactures specifications.

  • Install continues exhaust ridge vent ventilation system with an external baffle meet the asphalt roofing manufactures specifications.

  • We Install a Landmark shingle with Certainteed’s Integrity roofing system. We installed product specification which includes a metal drip and rake edges, a waterproofing barrier called Winterguard in all the vulnerable area’s and Diamond Deck roof protection over the entire roof. Replace all roof flashings. Landmark shingles offers the exceptional value of the industry’s toughest fiber glass mat and the strongest materials available. Because we hold the certification Select Shingle Roofer we and install the integrity roof system we are able to provide a 50 year NDL Transferable Warranty.

  • Remove the flat roof deck and insulation and treat the contaminated rafters. Fill the roof cavity with spray foam insulation so no air space is present for moisture or need for ventilation. This will also maximize Install new plywood roof sheathing and vapour barrier.

  • Install POLY ISO Tapered insulation for positive drainage to eaves and drains. Tapered insulation is custom fitted for every roof assembly. A roof schematic is sent to the manufacture and the insulation is laser cut and custom fitted and assembled on site.

  • We installed a Two Ply Roof System by Soprema. This roofing system features a self adhering system that enables us to a head gun at the seam. THE COLPLY SYSTEM is a heavy-duty two-ply roofing system installed over suitable insulation and substrates with cold adhesives Cap sheets are protected from ageing by lightweight colored granules. This product offer safety to both the building and worker as no hot tar or torching is required.



Expose roof and mechanical system

Expose roof and mechanical system.


Concrobium mold control

Treating rafters with Concrobium mold control. Vapour barrier not properly sealed, top plate not sealed. At the ceiling registers the vapour barrier was cut and never properly sealed.


Picture of attic prior to work starting

Picture of attic prior to work starting.


Water on the underside of the roof deck

Water on the underside of the roof deck caused by condensation. Rusted nails, water damaged plywood and insulation. Roof was dry and free from snow the day this picture was taken.


Light coming through the tongue

After the roof and insulation was removed we could see light coming through the tongue and grove cedar sealing. Possible  intrusion points through to the attic space. This was consistent through the entire ceiling.


2LB spray foam installed

2LB spray foam installed, rafters cleaned new roof deck being installed.


House pool roof section

2Lb spray foam installed sealing Mechanical system, Ventilation chimney’s, house pool roof section.





Why sealing attic leakage is so important. Warm air that escapes into the attic can rot the roof, cause mould, and in extreme cases like this one damage the interior and exterior walls. How can warm air rot the roof? In simplest terms, the warmer the air, the more moisture it can hold. As the cold air from outside enters the house and is warmed, it rises towards the ceiling. As it rises, it collects moisture that is generating within the house. When warm air touches a cold surface, the moisture is released and collects on the cold surface. The release of moisture is called condensation. In winter, you often see the effect on windows.


When warm air containing moisture touches a cold windowpane, moisture is released or condenses onto the windowpane and may begin to run down the pane collecting on the window frame or sill. If, over a long period of time, the moisture is not removed from surface of the window frame member, the surface may begin to rot. In the attic wood frame members, insulation and ceiling finish are all susceptible to moisture damage.


So when re-roofing a home especially older home that seldom have a vapour barrier you should make sure the house is well sealed from the attic to the interior living space and a proper ventilations system is installed in the attic. In addition all bathrooms are well vented with an exhaust vent that is sealed and well insulated out through the roof with a vent that has a damper. Just Adding more roof vent to a roof is not a system. There is a scientific approach with a proper calculation to ensure your attic is ventilated correctly. If you have a flat roof make sure it is properly sloped to the eavestrough gutters or drains.


Success! The following winter we had very little snow and a fairly mild winter, however last year 2010 we were featured on CBC to help educate homeowner’s ice damming because it was a bad year. I revisited the homeowners in June of 2011. SUCCESS. The customer had no ice damming, or water penetrating the roof, or any form of moisture in the attic. 


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