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Question DetailsAsked on 2/2/2016

Very loud mysterious thump in the ceiling above the first floor of 3-story house.

The thump occurs several times a day, usually in the evening. It is very loud on the first floor, coming from different places on the ceiling, not so loud on the second floor. It is unrelated to plumbing usage or to start and stop of hot water heating system. Sometimes two or three in a row a few minutes apart. Sometimes hours apart. Some days only one thump. Very loud, shakes the house. Sounds like someone drops a heavy book on the floor above.

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3 Answers


Below are several prior questions where I went overboard and listed all the possibilities I could think of - clearly, upstairs neighbors (if any) and overloaded roof and walls due to snow or ice load would be the obvious first things to rule out.

Because you have already ruled out water and heating - maybe - structural causes would be probably more likely. I would start with a definitive water pipe test anyway - several different times, run hot water for say about 5 minutes in upper floor sinks, then time how long after the thumping occurs - also note if there is a consistency in the timing relative to time of day or sunlight on a certain wall, because expanding and shrinking pipes and walls would be a very common cause of this sort of thump. With the pipes, especially if sewer rather than water pipes doing it, could take an hour or more for the sound to occur as the pipes cool. Since you say generally in the evening, could also well be cooling of the roof or a wall that shrinks and adjusts after starting to cool after having had sun exposure.

Otherwise - possibly expansion of wood in a floor due to a slow leak, especially if buckling up and popping tile or stone flooring loose from its thinset or mortar base, or gradually swelling floor or framing wood.

A more remote one, if heavy snow load - even if the roof structure is intact, if it is "flattening" the trusses or roof rafters due to being near its capacity, that can bow the top of the outside walls out, causing all sorts of tearing and thumping sounds in the walls - typically near the base where they fasten into the floor structure.

If you have outside deck or balcony, particularly if wood but can happen with concrete ones with water in the concrete expanding in freezing weather, is contraction of frozen wood - popping or thumping hard as it cools, especially if getting quite cold and popping free frozen points where the deck boards are frozen to joists. If this is the cause, you can commonly cause it to happen by going out about the normal time for it and walking around, causing the boards to pop free. Can happen every cold night (generally agood several hours after darkness falls and very commonly round midnight) for decades with decks that have enough moisture at the deck board/joist interfaces - commonly caused by melting frost or snowwater freezing at night and then popping free as the shrinking boards pull hard enough to break the frost bond.

One other less common cause (aside from ghosts) is gradual settlement of the structure due to foundation failure, or due to heavy insect damage or fungal rot (dryrot) causing gradual and progressive collapse of the structure - which can take years to become undeniably obvious in many cases, though generally exhibits drywall cracking around doors and such pretty early on after the noises start. Also tends to migrate around the house in many cases - not be tied to specific well-defined locations, as each area gives a bit and transfers some load to an adjacent area.

You said hot water heating system - this happens with baseboard systems when the pipes get hung up in tight spots in the framing or the framing sags, putting pressure on the pipes so they pop and thump as they expand and contract - though generally within 15 or so minutes after heating in a loop is coming on or shutting down, and generally in just a few well-defined repetitvie locations. Also happens more commonly with in-floor radiant heating, where it is heating up the surrounding flooring and joists and causes them, sometimes a half hour or more after the heat comes on or shuts the loop down. And note - the loop will commonly cause the boiler to come on when the thermostat first calls for heat, but the loop will continue to heat long after the boiler stops firing, so cooling contraction can occur an hour or more after the boiler stops firing. Especially common with in-floor radiant heating with metal radiator plates nailed under the floor decking too tightly, so they have no expansion room, and therefore pop and thump as they buckle or try to move against the nails or screws.

I would not commit to anything here, but since you said sounds louder in the ceiling than upstairs, and occurs different places in the ceiling, assuming your ceiling is not sagging (indicating possible floor joist cracking or excess sagging as the cause of the noise), then I would be voting for the hot water heating pipes as the most likely cause - either themselves or heating the wood around them.

One last thing, though this is awfully subjective - there is a difference between the sound being transmitted through the house and sounding loud because of that, and it actually "shaking" the house. If shaking the house - like it causes liquid in a container to generate ripples or chandelier to move or such, that is more than a pipe or popping joist would normally be expected to do - so if actuallyi "shaking" rather than just "thumping" the house, I would be looking for structrual causes, and if not up to a thorough inspection of all drywall and visible framing, should probably call a Structural Engineer for an inspection.

Answered 3 years ago by LCD


Thanks for the excellent response! Here are a few more details. The thumps started in September so snow is out as an explanation. The house was built in 1931 of brick and block with plaster over lath walls - no drywall (and no visible framing except for roof rafters). We have observed no sagging or cracking over 5 months of thumping so I think we can rule out water leaks. No structural work has been done to the house in over a decade. I tried the running the hot water test and it did not induce the thumps. We've definitely considered the possibility of ghosts. There is a small deck off the back porch but it is nowhere near the sound of the thumps. The hot water heating system is iron radiators and pipes, and the location of those pipes is consistent with where the thumps are coming from (my wife believes that there are a few well-defined locations for the thumps, and they are not close to the path of the regular plumbing pipes for the second floor but are on the path of the heating pipes). We will revisit that system for a solution, seven though the thumps started before the heating season began this year. We have bled them system (through the radiator in the attic, highest point in the system) and had the pressure checked by a local HVAC company. Perhaps an HVAC specialist with more expertise in hydronic systems could help. As to the thump vs. shake question, it falls more in the very loud thump category. No movement of chandelier or standing water. Never the less, after revisiting the heating system we will consider calling in a structural engineer. Thanks again.

Answered 3 years ago by lhbodian


OK - sounds like the freezing and snow load are out (assuming it is warmish in your area in September. Unfortunately, you say the noises started before the heating season - though I guess the pipes contracting as the house changed seasonal temperature and moisture could account for that.

I would go with the wife's thinking - try to tie down (maybe with dsticky notes noting number of times each place) the locations and see if pretty well confined to several, or random. If tied down, likely pipes moving, or moisture changes in the wood moving against the pipes.

Certainly, if the pipes (sounds like drain pipes here) are exposed (like in crawlspace or basement) I would go down there with some very heavy slick plastic - like pond liner plastic or ice and water shield, or even cut-open heavy plastic bottles, and anyplace there is a joint in the pipe close to or on/in a penetration through a joist or a wood brace the pipe sits on, nail a cradle of the plastic as an apron under it so the joint can slide smoothly on/through the wood. If as loud as you say, you should see scuffing and maybe splintering at the edge of the wood where the joint is catching on the wood.

Ditto to any metal hangers it is hanging from - you should see scrapes on the bottom of the pipe if it is moving thermally, then the hanger is "jumping" along the pipe after it gets at too sharp an angle. There are also roller-type hangers for that situation, which would work better.

Since you said loud in ceiling probably not open to see - in that case you might have to borrow or rent a fiber optic inspection camera (color ones are FAR superior for seeing what is going on), and drill a few about 1/2" holes in the ceiling to see where the sewer pipe is, and tyhen to follow along it to see if you can see places where it is hanging up. Might leave them open for awhile and look several times to see how the joints move around. (Camera rental about $20-40/day at Home Depot or tool rental place or some auto parts stores - cost about $75 at Amazon and Harbor Freight Tools and such for a decent home use one. Of course, works only in uninsulated spaces - which your ceiling likey is, but you never know till you drill the hole.

Answered 3 years ago by LCD

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