Trains and Cracks

04.27.2009 | HMMH |

by Lance Meister

Will the train damage my home?  This is a question we get all the time in our business.  The short answer is “probably not.”  Here’s the long answer:

Trains do create vibration, and if you live close enough to the tracks, you can probably feel it when the train goes by.  However, there is a very large difference between the point at which a human feels vibration and the point at which vibration can cause damage to even the most fragile structures.  Human sensitivity to vibration starts at around 65-70 VdB.  This is the point where you start to feel that very low frequency rumble and are maybe a little annoyed by it.  Damage to structure starts to occur around 95-100 VdB, and this is only for minor cosmetic damage, such as small cracks in plaster.

Because vibration, like noise, is measured on a decibel scale, every 10dB increase in the vibration level is a ten-fold increase in the energy of the vibration!  So the difference between 65 VdB and 95 VdB is not a 50% increase in the vibration, but a 1000 time increase in vibration.  That’s a pretty big difference between being able to feel vibration and having vibration cause damage to a building.

Another way to put this into perspective is to compare the vibration from a train to other sources of vibration you might experience in your home.  The vibration generated by a person running up the stairs, or slamming a door is equivalent to, or greater than, the vibration caused by a train in the nearby walls and floor.  Of course, you can always yell at your teenage son or daughter to stop running up the stairs and slamming the door to their room!  But the point is this: your house doesn’t suffer catastrophic damage when this occurs.  Houses are built to withstand some vibration.

A common occurence and something you may have experienced yourself, especially near new transit or rail lines, is that a person feels a train go by, senses the vibration, and then happens to look at a wall or the ceiling and sees a crack.  The immediate (and perfectly reasonable) response is to associate the two things.  The reality is that the crack may have been there for a long time and was just never noticed.  Buildings settle over time, and this can create small cracks in plaster.  In addition, seasonal variations in temperature and even the lowering of the water table under your house can put stresses on the foundation and walls and create cracks.  An older home may already have all these issues sorted out, but a new home may take some time to settle, and small cracks may appear over time, whether or not you live near train tracks.

This is not to say that it is impossible for the vibration from a train to create superficial cracks.  If the train tracks are located very close and the trains are traveling at high speeds, there is a small potential for some minimal damage.  However, if you can just feel the vibration, or are only slightly annoyed by it, chances are it is well below the threshold for damaging your home.