What goes bang in the middle of the night?

thompson1My first winter in Canada was spent in Thompson, Manitoba. We wore mukluks to school and played outside in the -40 weather. Quite a change from the English raincoats and shorts that we were accustomed to. At night, lying in bed we would hear loud bangs and cracks, like a gun going off. We were told it was the wood shrinking in the roof framing.

Yes that’s me in the photo. My first year of snow shovelling. Thompson, Manitoba , March 1968.



sewage frost compressedNow here in temperate Toronto, a common question from clients is why they hear ticking and banging noises in the walls. The most likely culprit is the plumbing drain pipes. Because these pipes are connected to the vent pipes that pass through the roof, they get very cold. Then, when warm water runs through the drain system, especially first thing in the morning, materials expand and give off ticking noises. The ticking sound is not the pipes leaking. If they were leaking the stains would soon show up somewhere in the house. This phenomenon can occur with ABS ( black plastic) drain piping, but will be even more likely with copper drain piping. The copper drain piping was common in construction in the 1950s, 1960s and early 1970s. The ABS piping came in to common use in the early 1970s and is still used today.



vent pipes older

These are vent pipes in an attic in an older house built in 1950. Copper pipes serving as vents for fixtures in the house are connected in the attic to one cast iron pipe that passes through the roof. You can see how these pipes would be really cold in the winter, as they are exposed to exterior temperatures. The vent pipes allow air in to the plumbing drain system so water can flow in the drains without siphoning the traps empty. Vent pipes may slope back towards the fixtures or in the opposite direction, as long as there are no low spots where water can collect and block the vent pipes.




Other common sources of noise:

  1. Animal activity. Usually scratching sounds or footstep sounds.
  2. Flap on a fan exhaust damper moving ( it takes very little wind to move these).
  3. In extreme cold weather, contraction of structural members in the attic. Loud bangs, like firecrackers going off.
  4. Loose soffit panel, or metal flashing or fascia metal or wood flapping or a shingle flapping.
  5. Tree branches striking the house.