Most of the bangs and ticking sounds in the attic during a deep freeze are just wood and metal moving, but a few sounds deserve a closer look.
It is two in the morning, the temperature has dropped well below minus twenty, and something overhead goes bang. A few minutes later there is a slow creak, then a sharp tick, then silence. Plenty of Calgary homeowners lie awake wondering whether the roof is about to give up.
In most cases the answer is no. A house is a structure made of wood, nails, metal and insulation, and every one of those materials reacts to a cold snap in its own way. The noises are the sound of the building adjusting. Still, a few sounds point to real trouble, and it helps to know the difference before you spend a night staring at the ceiling.
Why Cold Makes a Roof Talk
Wood shrinks as it loses moisture and as it cools. Trusses, rafters and plywood decking all contract during a hard freeze, and they do it unevenly. The top of the truss sits in a frigid attic while the bottom chord rests against warm ceiling drywall, so the two ends of the same piece of lumber are living in different climates.
Where wood meets wood, nails and plywood edges grip each other through friction. As the framing shrinks, that grip lets go all at once rather than gradually. The result is a loud pop, like a knuckle cracking. It sounds dramatic because the attic works like a drum and carries the sound down to the bedrooms.
Thermal Movement in Trusses and Decking
Roof trusses are engineered to move a little. The top chords stay cold while the bottom chords stay near room temperature, and that difference can make a truss bow slightly. In some homes the bottom chord lifts a hair off the interior walls it normally rests on, and drops back as the weather warms. Builders call this seasonal truss movement, and it is a known quirk of wood-framed roofs rather than a defect.
Plywood or OSB decking expands when it takes on moisture and shrinks when it dries. A Calgary winter is very dry indoors and bitter outdoors, so the sheets move at their seams and edges. Rows of fine ticking sounds across the attic often come from sheet edges rubbing past each other. Sound that comes in a pattern, a pop here and a tick there every few minutes as the temperature falls, is almost always this kind of movement.
Metal Expands and Contracts Too
Metal moves more than wood. Roof vents, flashing, chimney caps, eavestroughs and standing seam panels all lengthen and shorten with temperature. A metal flue pipe passing through the attic will tick and groan as a furnace cycles on and off, because the pipe heats and cools quickly.
Eavestroughs and downspouts add their own noises. Ice and frozen meltwater inside them grip the metal, and when the sun hits the north side of the house or the temperature rises a few degrees, the metal slides against the fasteners with a snap. Sunny afternoons following a very cold night are a classic time for these sounds, and the same goes for a Chinook arriving after a deep freeze.
Metal noises are usually quick and sharp. Wood noises tend to be deeper and louder. If you can tell which one you are hearing, you already have a good clue about the source.
Sounds That Are Normal
A few patterns are reassuring. Loud pops at night during a sharp temperature drop are normal. Ticking in the early morning as the sun hits the roof and the house starts to warm is normal. A creak that happens once or twice when the furnace kicks on is normal. So is a noise that comes from the same spot at the same time of year with nothing else changing.
Age plays a part too. Newer homes in Calgary often make more noise in their first few winters because the lumber is still drying out. Older houses settle into their own routines, and the sounds become part of the background.
Sounds and Signs That Are Not Normal
Some sounds, and the things that come with them, deserve a call. Pay attention if you notice any of the following:
- A long, continuous groan or crack while snow sits heavy on the roof, particularly if doors or windows start to stick at the same time.
- A visible sag in the ridge line or along a rafter run, which you can check by looking at the roof from across the street.
- New cracks in drywall near the ceiling corners that widen over a few weeks.
- Nails pushing up through the ceiling drywall in a line, which can point to a truss lifting away from its partition walls.
- Daylight showing through the roof boards from inside the attic.
- Sagging or dampness in the insulation, or frost building on the underside of the decking.
Ice load is a separate concern. A heavy, wet snowfall followed by a hard freeze can put real weight on a roof, especially above a low-slope addition or where drifts collect against a taller wall. Heavy ice at the eaves also hints at ice damming, which can lead to water backing up under the shingles. If a house has a history of sagging or poor framing, that is the time to get a professional look instead of waiting for spring.
Why Some Attics Are Louder Than Others
Two houses on the same street can sound completely different in the same cold snap. The difference often comes down to what is happening in the attic.
An attic with good insulation and balanced ventilation stays close to outdoor temperature. The wood is cold all the way through, and it moves in a slow, even way. An attic that leaks warm air from the house, through ceiling fixtures, hatches or gaps around ducts, develops warm and cold patches. Parts of the framing heat up while neighbouring boards stay frozen, and the uneven movement makes more noise. Those same warm patches melt snow from underneath, which feeds ice dams at the eaves.
So a very noisy attic can be a clue about air leakage rather than a structural problem. If the sounds come with frost on the nails, icicles that grow fast along one side of the house, or rooms that never seem to warm up, the roof is telling you something about the insulation and air sealing below it.
Ventilation plays its part as well. Soffit vents that have been stuffed with insulation block the airflow that keeps the deck cold and dry. Fixing that is usually simple, and it quiets the roof as a side benefit. A roofer or an insulation contractor can check the vents from outside and from the attic hatch in a single visit.
What You Can Check Yourself
On a calm day, stand in the yard and look along the ridge and eaves. A straight ridge line is a good sign. Look at the shingles for lifted tabs or missing pieces, and check the eavestroughs for ice that has pulled them away from the fascia.
In the attic, bring a good flashlight and wear sturdy shoes. Stay on the joists or a plank and never step between them. Look for frost on nails, dark staining on the decking, gaps where insulation has slumped, and any cracked or split lumber. Frost on the underside of the roof deck means warm, moist air from the house is escaping into the attic, which has nothing to do with the noises but matters for the long-term health of the roof.
Take photos of anything unusual and note the date. A record of how things look in January makes it much easier to tell in April whether something has changed.
Listen, Then Look
The pops and creaks of a cold night are mostly the house doing what houses do in a Calgary winter. Sharp, short, patterned sounds that come and go with the temperature are normal. Steady groaning under snow, visible sagging or new cracks in the ceiling are not, and they are worth a closer look.
If you are not sure which camp your roof falls into, a proper roof inspection for Calgary homes will tell you what the framing, decking and shingles are doing, and whether the sounds overhead are harmless. It is easier to sleep through a cold snap once somebody has actually looked.
About the author: this article was contributed by the team at Angel’s Roofing, a Calgary roofing company that is COR certified and BBB accredited. The crew installs and repairs residential roofs through Calgary’s hail, wind and freeze-thaw seasons.