Repetitive knocking sound coming from ceiling…what is it??

[Anonymous]

Started a few days ago. I don’t think it’s water dripping. It’s not an animal. We had some roof work done recently but it hasn’t rained in days, and there’s another floor between this ceiling and the roof. It’s not plumbing because it happens even when no faucets or appliances are on. Is it heat related?

[Anonymous]

Three knocks of death? Poltergeist? Air duct?

[Anonymous]

There is an iron (?) pipe that makes loud sound when expanding. I forgot what that was for. It sounds like something is dripping, but it goes away pretty quickly, within a minite. The plumber said people call him all the time thinking there is water dripping.

[Anonymous]

Acorns?

[Anonymous]

Could be pipes or ducts expanding and contracting.

Or woodpeckers.

[Anonymous]

water hammer?

[Anonymous]

woodpeckers

[Anonymous]

Ya it could be water hammer. It’s like from a fast wave running through your pipes when you first turn on the tap. I don’t think it’s a big problem but google it?

[Anonymous]

Does it happen when the furnace kicks on? Expanding duct work can do it.

[Anonymous]

Anonymous wrote:Could be pipes or ducts expanding and contracting.

It's this. We have it too

[Anonymous]

Anonymous wrote:

Anonymous wrote:Could be pipes or ducts expanding and contracting.

It's this. We have it too

We do, too, but we also have what I think (hope) is an animal that sometimes causes knocking noises in quick succession.

[Anonymous]

Ghost
Squirrel

[Anonymous]

Anonymous wrote:water hammer?

NP: Not the water hammer because OP said it's happening when the water is not running. We have a water hammer issue, it's enough to drive us crazy. Anyhow OP my guess is you have a squirrel on your roof or another critter/bird.

[Anonymous]

My water pipes (PVC) squeak sometimes because they are up against the wall foam insulation and also wooden boards. They are surprisingly squeaky and at times I hear a lot of tapping that sounds like a water leak. In my case is was just a nuisance but not a problem.

[Anonymous]

Ghost. Lol.

We have loud knocking occasionally, and it is a woodpecker. Sounds like it is coming from the ceiling -- but it isn't. It's the bird outside sitting on the gutter pecking at the house.