My 5th (top) floor apartment is shaking; what might cause this?

Question

I live in a developing country (so don't have much faith in building codes), and have been experiencing increasingly noticeable and frequent "shaking" in my top fifth floor apartment. I'm seriously concerned.

My home has been shaking. I have felt small tremors from an earthquake before, and this is the best way to describe it, however, I do not currently live in an earthquake zone, so this is quite worrying.

The "shaking" bouts seem to last for about 5-10 seconds, by my estimate; I should also note that this country is not an earthquake zone. My home is the top floor of a five story building, that is rather "skinny" (in my judgement, something like a 2.5 - 3.5 : 1 X:Y ratio. When I first began experiencing this shaking a couple of months ago, I thought that it might have been the bed, or even just my imagination, and paid it little attention. However, over the past few weeks, the shaking has become markedly more noticeable, and I confirmed that my girlfriend also felt it. I made a query with the landlord, but I was told that there was no problem, or that it was "the wind". After some research on the internet, I found that buildings do indeed sway slightly with wind, and so felt at least somewhat placated in my perhaps overblown fears of building collapse.

However, today, I felt the most violent instance of shaking to date in the late evening, and confirmed that my girlfriend also felt it. This had me very concerned, so I took the step of also asking the tenants on the floor below, and they also confirmed that they had felt the shaking. Based on our positions at the time of the shaking, it was apparent that the shaking was felt at least on the 4th and 5th floors of the building, and at all locations, as I was in the middle, my girlfriend was on the "left", and the other tenants were on the "right" at the time of the occurrence of the shaking. There was absolutely no wind, and as it was late night, there was no construction going on that may have caused vibrations or such.

I should also note that since I moved into the apartment, there has been ongoing construction on the lower level floors; I obviously have no idea, but my fear is that they may have weakened a key supporting wall or some such.

I decided to leave the building immediately, and I'm currently in a hotel, and plan to cancel my lease and find a new place to live.

So, my question to you, in your opinion, am I overreacting, or is something reasonable likely to be seriously wrong with this building? What sort of tests would a structural engineer perform to determine the cause of the shaking / if a building like this is safe? I ask because it may be that the landlord says she will hire an engineer or some such to look into the problem, and in this case, I want to be sure that my fears are sufficiently placated, as right now I have absolutely no desire to move back into my apartment.

Hope you can help shed some light on this rather scary situation of mine!

Answer 1

"Normal" building movement would only be due to wind or earthquake. Movement due to normal wind would only be slightly apparent to very sensitive individuals in very tall buildings, as in dozens of floors. Most people would notice slight wind movement in very high winds or minor earthquakes, but nothing alarming. The only alarming movement anyone would notice would be during strong earthquakes.

How much a building moves due to a lateral force such as wind or earthquake depends partly on the buildings height to width ratio and the relative rigidity of the building's structural elements. The critical width when determining the height to width ration is the building's critical (narrowest) depth in the direction of the force. Since wind and earthquakes can come from any direction, we can simplify and say the least horizontal dimension.

Sometimes people in buildings will sense vibrations caused by passing trains, or even heavily loaded trucks. Some types of soils have a certain elasticity that transmits vibrations from heavy movement into the building's foundation and up into the structure. These movements are primarily vertical in direction and would typically not be threatening to the building, though repeated severe vibrations can cause brittle finish materials such as plaster work to crack or even fall out of position.

A similar movement can be caused just from people moving normally on a particular floor system, especially in smaller buildings, because the floor structure is overly elastic. This usually would not indicate any structural failure is imminent, rather that the structure was not built adequately from a usability standpoint.

Renovations to existing buildings must be carefully planned to avoid disturbing structural, load bearing elements. Not just bearing vertical loads, but lateral loads as well. If they must be disturbed, adequate temporary shoring must be in place until proper permanent structure is replaced. Even if shoring was not done, building movement would not be discernible unless structural failure was imminent. Imminent in building failure can be anywhere from within the next few minutes to happening over a period of several months.

Besides wind, earthquake, heavy vehicles, and compromised structure, the only other cause for building movement would be differential settlement due to foundation not being founded in stable soil materials. This is actually a subset of structural failure, as stable soils is a necessary part of a sound structure.

When an engineer assesses a structure for soundness, testing may or may not be done, depending on the situation. Structural testing often means testing to failure, which is often not feasible in an occupied structure. The engineer will make an assessment based mainly on inspection of existing conditions and comparing with the building's plans to see if it was built in accordance to the plans, if the plans have design errors, if there are signs of failure such as cracks of certain form in certain locations or sagging and deformation of structural elements.

Some small scale materials tests can be done to verify the installed material matches the design specifications by taking samples and testing in a laboratory. Only after considering all available evidence will the engineer make an assessment based on the evidence and his/her experience and knowledge. They would typically publish a report summarizing what they did, what they observed and their findings. While such reports are quite technical by nature, the main gist of it should be comprehensible to any reasonably intelligent person without an engineering background.

It's impossible to say if you overreacted since I was not there. While there is certainly cause for concern, imminent collapse World Trade Center style is highly unusual. I've seen many obviously failed buildings in developing countries in which squatters live without incident for years. Yet one would have to be truly desperate to spend time in such buildings, as sudden catastrophic collapse does remain a possibility.

Answer 2

Normal Vibrations in Buildings Have Identifiable Sources

I've encountered a vast range of vibrations in multi-dwelling buildings I have lived. Hear are the ones I can remember:

• washing machine spin cycle (this happens often and, if it matches the resonance of the building can travel throughout multiple floors)
• dishwasher valves and drain pump (not very strong, but once the sound filtered through floors and walls, the sound and feel was disconcerting)
• nearby trains
• nearby garbage trucks and other heavy vehicles
• dancing at house parties
• active construction work
• elevators
• earthquakes
• explosion nearby

Note that all these sources are not the building structure itself, and are fairly easy to track down. I can't remember encountering a source of vibration or shaking whose source I could not pinpoint with a small amount if work.

Find the Source or Move Out

The most likely explanation for the vibrations/shaking is that it is being caused by something in or near the building and not the building structure itself. With a reasonable amount of effort by you, your neighbors and landlord, you should easily be able to pinpoint the source of the vibrations/shaking.

If you still cannot pinpoint the source after putting some earnest effort into finding the source, it may actually be the building structure itself. This is not that far fetched if the building was not engineered (building inspectors usually defer to a professional engineer for structural issues).

If your only conclusion is that the vibration/shaking is originating from the building structure itself, then you should move out - it is a bad sign. Even if the building doesn't collapse, you will have made the correct decision with the information you had at hand at the time.

Answer 3

You will have to do a bit of investigation to decipher external causes (e.g. trains etc.).

Thereafter maintain a daily log with times, degree of movement and any other relevant information. Get your friend to stay and report on a cell phone the movement while you are outside checking the source.

If it still does not help a good engineer would be useful but very expensive. But if you are not having the peace of mind, leave the place and take action to get the deposit back and inform the owners and the authorities.

Cheers