Loud noise in attic

February 22, 2022 5:08 PM

I am hearing a loud noise in my attic from time to time, maybe once a day. It sounds like someone dropping a 5 pound weight. What could it be?

I have not been up to the attic since moving in since the access is very hard to get to. I am thinking it is related to thermal expansion. The noise always seems to be generally in the same place above the room. A few times it was at the same time of day (mid morning or in the evening). I also know this ceiling was replaced not long ago. However, I can't think of what it could be except perhaps some joists rubbing against each other and causing friction. It is a very loud thudding noise that sounds the same each time.

Once I am able to go into the attic, what should I be looking for to get it to stop?

posted by roaring beast to Home & Garden (20 answers total)

Is there a bathroom that may or may not be venting nearby? Reason i ask is that sometimes these fans have a somewhat noisy door that opens when the fan is on which can sometimes noisily close when the fan turns off.If the fan is humidity-controlled, this would not necessarily be something you'd do with a switch or, if you live in a multi-unit building, could be something someone else was turning on and off. Just one possibility of many, but at least a non-worrying one.
posted by jessamyn at 5:16 PM on February 22, 2022 [3 favorites]

Are you in a single family home?
Is it over or under 70 years old?
Roughly where in the world are you, and is it a city or rural or?

On balance: you have a raccoon. Or maybe some odd machinery and/or vents up there, and traps or wadding/insulation may help.
posted by SaltySalticid at 5:16 PM on February 22, 2022 [4 favorites]

Clearly a ghost, or a raccoon. Marginally possible that you have a ghost raccoon. You will either require an exorcist or someone trained in getting pregnant critters out of attics. (It’s that time of year)
posted by donut_princess at 5:22 PM on February 22, 2022 [23 favorites]

I'd think most likely an animal or large bird. Thermal expansion, yeah mayyybe, but I'd think that would be more a series of small pops than one big thud. I'm having trouble imagining something that could hold back that much force, then release it suddenly. Unless you see any flat sheet metal that could be warping, that can make a surprisingly loud sound. If there's any square ducting up there, maybe poke all the flat sides to see if you can recreate the sound.
posted by ctmf at 5:31 PM on February 22, 2022 [1 favorite]

Best answer: Thermal expansion, yeah mayyybe, but I'd think that would be more a series of small pops than one big thud.

That hasn’t been my experience. When it happens to our house it’s generally one big, loud BANG. Happens once a day, usually at around the same time, often in the evening. Very unnerving.

Is it cold right now where you live? Are there big temp differences between day and evening? Our roof has been making the noises you describe for the last couple days because it went from +10C to below -20C with the windchill (-4F). It startles the heck out of me even though I know what it is and it happens every winter—it sounds like a really loud bang or a cracking noise and is pretty freaky. But it’s harmless.

Here’s an article on it: Dramatic temperature change gets that roof popping
posted by hurdy gurdy girl at 5:40 PM on February 22, 2022 [10 favorites]

This reminds me of a chapter from La Maison de Claudine by Colette. In the story, the noise turned out to be an owl.
posted by maggiemaggie at 5:47 PM on February 22, 2022

If it were an animal you'd hear it more often.

Is there snow where you are? We get a lot of "fooomph!" type noises when the sun warms the snow and it falls off the roof.

It's also very possibly some mechanical equipment. You might have an air handler up there or a vent like Jessamyn mentioned.

Any big birds in your area? Sometimes a wild turkey will land on our roof. Yes, they do in fact fly somewhat, though probably not when dropped out of a helicopter.
posted by bondcliff at 6:06 PM on February 22, 2022 [6 favorites]

Seriously, once you get up there, take a TON of pictures, and then examine them back downstairs. Take a light, maybe wear a mask, depending on the ventilation & light.
posted by wenestvedt at 6:39 PM on February 22, 2022

Any trees around that animals could be jumping off of, onto your roof?
posted by Knowyournuts at 7:10 PM on February 22, 2022

A single bang that happens no more than once per day is almost certainly linked to the day's thermal cycle rather than anything smaller-scale. You might not be able to get rid of it because it might be inherent in the design of your building. Give some consideration to instead working out when it's going to happen, so that it just becomes a thing instead of a potential threat.

Logging the exact times at which you hear the bang, and cross-checking your log against your local weather service's temperature and wind observations for your area, would be a good start.
posted by flabdablet at 7:16 PM on February 22, 2022 [8 favorites]

Response by poster: Single family home, about 50 years old, no snow. I noticed it more when the temperatures were changing more, but less since it has been consistently cold, which leads me to think thermal.

I don't think it is animals with the consistency of the noise and the location, and it being such a loud banging sound. It definitely sounds like it is IN the attic, and there is nothing above.

hurdygurdygirl's article seems to be a good explanation, but doesn't point to many solutions. Googling that brings up a lot of other good articles, so that seems like a good place to start.
posted by roaring beast at 8:01 PM on February 22, 2022 [1 favorite]

Response by poster: Here is another answer from Quora:

You didn’t say where you are writing from, but we get that effect during many nights throughout the winter. It gets bloody cold in the attic. There’s a lot of wood up there, joined to other wood with nails and screws. When the attic has been warmed by the sun all day (warmer than the outdoor air temp) and the outdoor air temperature drops 20 degrees from the daytime temp, bringing the attic temperature with it, for a swing of maybe 30 degrees, the rafters or trusses build up pressure between one and another. The bottom span of each truss (or tie beam if you have rafters) is the ceiling joist, meaning that that part of it is at the same temperature as the room underneath it. But the rest of the attic, above the insulation is at the same temperature as the outdoors. That puts a lot of strain on the wood and on the other parts that are attached to it.

It eventually releases, rather like the tectonic plates in the Earth when they slip and create an earthquake. Instead, you get a loud bang that sounds like somebody dropped a car on the ceiling. Different areas of the attic might equalize at different times, so you get more than one loud boom.

All the parts of the house are connected, one to the other to the other, so yes, that energy gets transmitted down the wall studs to floors below, and scares the cat.

If it’s the temperature differential and the structural members equalizing, there’s not much you can do about it.

posted by roaring beast at 8:10 PM on February 22, 2022 [2 favorites]

Haven't seen these questions:

Are there pine trees, sweetgum trees, or oak trees overhanging the roof? It could be pinecones, "gumballs", or acorns hitting the roof. Could also be small dead branches.

Are there _any_ nearby branches? Sometimes squirrels will jump from a tree onto our roof on their way somewhere
posted by TimHare at 8:23 PM on February 22, 2022 [1 favorite]

A hammering pipe?
posted by JohnnyGunn at 12:28 AM on February 23, 2022

+1 large bird.
posted by pompomtom at 12:46 AM on February 23, 2022

You don’t mention if you have duct work up there, but as others have mentioned a piece of sheet metal suddenly inflecting can make a very loud noise.
posted by Tell Me No Lies at 1:41 AM on February 23, 2022 [3 favorites]

It sounds like someone dropping a 5 pound weight. What could it be?

Definitely thermal expansion. A critter would be making noise more often.
posted by Thorzdad at 4:46 AM on February 23, 2022 [4 favorites]

If it were a raccoon, you'd know that already; they're talky bastards and don't tend to stay in one place or follow a routine. If it were some other kind of animal you'd be hearing scratching and skittering noises, not big thumps. If it were a bird it would... not sound like that unless the bird is really into weightlifting or something.

It's thermal. I live in an old house with modern additions; the wild freeze-and-thaw cycles this year have made the place thump and rattle like never before: small pops, big thumps, long creeeeeaks, and everything in between. You live in an old house with a new ceiling, so I'd not be at all surprised you're getting similar effects from new materials still settling in with older stuff. (Or there's a chance it's something in your heating system expanding and contracting with the thermostat cycles, rather than the house itself, I suppose.)

As far as I know the only solution is to decide to consider it a charming feature of the house rather than an annoyance, and wait for spring.
posted by ook at 6:41 AM on February 23, 2022 [1 favorite]

Just to note that when I had attic raccoons, it sounded like people were moving furniture up there, not like a distinct one-time or occasional bang. Lots of scooting and frolicking about.
posted by Occula at 7:11 AM on February 23, 2022 [2 favorites]

My house makes a noise where the porch meets the roof and it's thermal expansion. It took far too long to figure out what was causing the noise which sounds like a big bump. This is because the sound is not what I expected - how does the house shifting as it cools result in a loud thump? It's not like I actually knew what that should sound like mind you, just not that. Plus it doesn't bother my spouse at all, despite sounding a bit like someone slamming a door shut.
posted by zenon at 7:45 AM on February 23, 2022 [1 favorite]