Attic and envelope
Attic Rain Repair in Calgary
Attic rain in Calgary is winter frost melting off the underside of the roof deck. Axion Roofing fixes the air leakage and ventilation causing it instead of replacing a sound roof.
Attic rain is not a roof leak. Attic rain is frost that accumulated on the underside of your roof sheathing all winter, melting during the first warm stretch and dripping through the ceiling. Axion Roofing fixes the cause, which is warm moist air leaking from the house into a cold attic, and does not sell you a roof you do not need.
Calgary produces attic rain more reliably than most Canadian cities because chinooks swing the temperature 20 degrees or more in a day. The frost that built up over three cold weeks releases all at once.
01 / 05
How to tell attic rain from a roof leak
| Symptom | Attic rain | Roof leak |
|---|---|---|
| Timing | During a thaw, often days after the last snowfall | During or within hours of rain or snowmelt |
| Location | Ceiling light boxes, bath fans, around the attic hatch, along exterior walls | Directly below a roof penetration, valley or wall intersection |
| Season | January through March | Any season |
| Attic evidence | Frost or a white rime coating the underside of the sheathing and the nail points | Wet or stained sheathing traced up-slope to a specific penetration |
| Pattern | Multiple rooms at once | One localized area |
If your ceiling only wets during a warm spell in February, replacing the shingles will not stop it. Roof leak repair in Calgary covers the other case.
Where the moisture starts
Warm wet air leaking into a cold attic
01Flex duct laid over uneven loose fill. Every unsealed penetration is an air-leakage path.
02Blown-in insulation disturbed around a vent duct, leaving the ceiling plane open.
03A metal exhaust duct terminating into the attic instead of through the roof.
02 / 05
The three causes Axion Roofing corrects
- 01
1. Air leakage through the ceiling plane
Warm indoor air carrying moisture rises through pot lights, the attic hatch, plumbing stacks, wiring penetrations, top plates and bath fan housings. It hits the cold sheathing and deposits as frost. Sealing those penetrations is the single highest-impact fix. - 02
2. Exhaust fans discharging into the attic
Bath fans and dryer vents that terminate inside the attic instead of through the roof or wall dump litres of moisture into the space every week. Axion Roofing checks every termination and reroutes the ones that discharge into the attic. - 03
3. Insufficient or unbalanced ventilation
The National Building Code, Alberta Edition, Section 9.19 requires an unobstructed vent area of at least 1/300 of the insulated ceiling area on standard slopes, with at least 25% of the openings at the top and at least 25% at the bottom, distributed on opposite sides of the building. Section 9.19 also requires at least 63 mm between the top of the insulation and the underside of the sheathing. Insulation blown over the soffits blocks intake, and exhaust vents without intake do nothing.
03 / 05
The repair sequence
- 01Inspect the attic and photograph the frost line, the insulation depth, the soffit intake and every ceiling penetration.
- 02Air-seal the ceiling plane: hatch, pot lights, top plates, plumbing and wiring penetrations, bath fan housings.
- 03Reroute exhaust terminations that discharge into the attic.
- 04Reopen blocked soffit intake and install baffles to maintain the required clearance at the eaves.
- 05Balance exhaust to intake and add ridge or static venting to meet the code ratio.
- 06Restore insulation to full depth and coverage once the sealing work is complete.
Step 6 is where attic insulation in Calgary picks up, and the two jobs are usually done together because the attic is already open.
04 / 05
Why order matters
Adding insulation before air-sealing makes attic rain worse. Deeper insulation makes the sheathing colder, which increases frost deposition from the same air leakage. Axion Roofing seals first, ventilates second and insulates last.
From the jobsite
Attic rain, not a roof leak
Water-stained decking, vent openings and duct terminations: the evidence that separates the two.
Click any photo to enlarge
Water stained deck boards and rafter close up 
Deck opening showing metal flue and attic insulation 
Installing new roof vent through cut deck opening 
Flex duct run through attic insulation close up
05 / 05
Damage attic rain causes if it continues
Repeated frost cycles delaminate roof sheathing, wet and compress insulation until it loses R-value permanently, stain drywall, and support mould growth on the underside of the deck. Sheathing that has cycled wet for several winters gets replaced during the next roof job, which is why Axion Roofing photographs deck condition on every roof inspection in Calgary.
Book a free attic and roof assessment in Calgary, or see the full range of Calgary roofing and attic services Axion Roofing provides.
Sources
- National Building Code, Alberta Edition, Division B, Section 9.19 Roof Spaces.
Free estimate
Fix the frost, not the shingles
Replacing a sound roof does not stop attic rain. Air-sealing and ventilation do.