Cold related sounds or damage

[PJD]

This morning while getting ready for work I heard a "really" loud noise in the house. This is not the first time in these extremely cold temperatures but here's what scared me - it was a huge thump like something fell or something and the house shook. I am not kidding, I was in the bathroom & it shook.

I know there's no way for anyone to know what caused it but does anyone think it could have come from the attic? I am spooked by it and wondering what I need to inspect. I will check the attic but does anyone have any other plausible explanations?

I had to leave to catch the train so I couldn't do that this morning but I peaked out the window to the back of the house and saw nothing. I looked on one side of the house outside and no sign of anything. I forgot to check the other side, lol. Just checked the side the bathroom is on. We do not have enough snow on our roofs to cause problems. At a quick glance it didn't appear to come from outside...

Any insight or suggestion would be greatly appreciated. Thanks in advance.

[R_D_G]

It's called cryoseism.

I first heard it on Christmas eve. It made for a good story for the kids.

http://www.cbc.ca/news/canada/toront...ight-1.2482615

I too was concerned and went to the attic to make sure that no tree branch had gone through the roof.

R_D_G

[Inspector Phil Acker]

The noise is most likely due to relieving of stresses that build up in wood framed homes. The most common occurance location is with engineered attic trusses. The top and bottom members are called "chords" and the interconnecting members are called "webs". Metal plates join the members together.

In cold weather, there is a significant temperature differential between the bottom chord [covered by insulation and essentially at room temperature] and the top chord [essentially at the outside ambient temperature]. In cold weather, framing elements tend to bow. So the top chord bows, which in turn pulls up on the webs, which in turn pulls up on the bottom chord. The net result is that stresses build up in the joining [gusset] plates. If there is a significiant change in outside temperature and humidity, the stresses build up quickly. The load bang is when the stresses reach a level such that the joints suddenly relieve the built-up stress.

The sound is very sharp and load, similar to a gun going off. For engineered trusses, this does not do any damage to the trusses.

This condition can also happen within outside walls. The phenomenon is similar: wood studs tend to bow out in cold weather, which may build up enough stress to cause a dramatic release in pent up energy within the wall structure.

[R_D_G]

Originally Posted by Inspector Phil Acker

The noise is most likely due to relieving of stresses that build up in wood framed homes. The most common occurance location is with engineered attic trusses. The top and bottom members are called "chords" and the interconnecting members are called "webs". Metal plates join the members together.

In cold weather, there is a significant temperature differential between the bottom chord [covered by insulation and essentially at room temperature] and the top chord [essentially at the outside ambient temperature]. In cold weather, framing elements tend to bow. So the top chord bows, which in turn pulls up on the webs, which in turn pulls up on the bottom chord. The net result is that stresses build up in the joining [gusset] plates. If there is a significiant change in outside temperature and humidity, the stresses build up quickly. The load bang is when the stresses reach a level such that the joints suddenly relieve the built-up stress.

The sound is very sharp and load, similar to a gun going off. For engineered trusses, this does not do any damage to the trusses.

This condition can also happen within outside walls. The phenomenon is similar: wood studs tend to bow out in cold weather, which may build up enough stress to cause a dramatic release in pent up energy within the wall structure.

The strange thing about this noise is that everyone seems to have heard it at the same time. What are the chances of multiple houses relieving the built-up stresses in the frames at the same time? I think it is more likely that the sound was caused by a common event that everybody in the neighborhood heard.

RDG

[PJD]

Thank you very much for both of your responses. I feel a lot better.

[homie27]

I'm experiencing the same issues. I think in my case at least, its caused by what RDG is describing. I live in an area of new houses (about 4 years old) and others on my street are hearing these noises. plus i'm sure alot of houses use these use engineered attic trusses. but just in case, who do I know my house has engineered attic trusses?

[Mark & Lynda]

Originally Posted by homie27

plus i'm sure alot of houses use these use engineered attic trusses. but just in case, who do I know my house has engineered attic trusses?

They all do.

the trusses are delivered to the job sites ready to install.

[homie27]

but how do they look like? are they just 2x4s or do they look different? or is it how they are joined together? are they designed to be able to handle these stresses caused by the cold? also, would it be a good idea to have foam insulation sprayed against the inside of the roof so the attic and the truces doesn't get so cold?

[gerapau]

Yes, mostly 2x4s with metal plates where they join. Yes, they are designed to take these stresses. Not a good idea to spray foam where you are mentioning. Besides, the top chord would still be on the outside of the insulation and could still cause the same noise.

We have an open area on our main floor where the roof trusses span about 35-40 feet without any walls under them. When we first moved in we mentioned this noise to the builder and were reassured that it is very normal. It was explained to us that the larger the span that the truss covers the more the stresses build up and the louder it can get. Ours can be very loud when they "crack". But after 3 years we are used to it.

[homie27]

thanks for the reply. just curious, why isn't it a good idea to spray foam under the roof?