Expert: Bruce E. Johnson - 1/10/2009

Question
QUESTION: i heard a loud crack--in the middle of the night of course--and assuming it was the outside electric box ignored it as it had happened before but then i noticed what appeared to be a water stain on the ceiling below an upstairs bathroom but no drain is nearby where the stain is. a couple of people have said it is not a water stain but a drywall crack (i don't see how it could have made such a loud noise!)--it is near, or rather alongside maybe, a aircon/heat duct--and i'm hoping it is not a broken truss or something.  i am disabled and cannot get upstairs to crawl into the attic to look for myself so any idea you may have would be appreciated so i can know who to go to for help in fixing the problem.
thank you.

ANSWER: Hi janni, you didn't mention where you lived or what the weather conditions were when you heard the noise.  Houses are like living things they breathe in and out, expand and contract, move up and down from the soil conditions and  side to side from external forces like wind and the elements.  Any of these things can cause cracking or popping sounds.  If the weather has been extremely cold where you live it might have been any number of contraction noises caused by the building materials shrinking in size.  Some materials shrink or expand differently than others.  If this is the case and the two materials are attached to each other, one of them may not budge and this relieving of tension will will make a noise.  At this point in time I wouldn't worry about it.  It sounds like it was just a natural house noise that may or may not repeat sometime in the future.

I hope this information helps feel free to write again regarding this or other matters, sincerely bruce e johnson..bejohnsonconsulting.com

---------- FOLLOW-UP ----------

QUESTION: thank you for your reply but no, it was not the usual expand and contract noise--which i am used to--it was so loud that it woke me up; it has left a greyish stain and a slight outwards bulge in the crease between the wall and the ceiling near a corner (there is a pocket door just to the side and the corner abuts my bedroom doorframe); my bedroom is a separate one-storey building from the other two-storey part with its own roof and the problem part is an inside wall attached to an inside wall. i have two other drywall cracks from the house settling and they are not like this one and it hasn't happened anywhere else in the house, or again, but has left evidence--the greyish mark-- behind. i live in locust grove, va.--on the whole i keep the house both winter and summer at 65-69degrees and do not use heat or aircon if the weather is not too hot or cold.

Answer
Hi again Janni,
If your home has experienced settling issues over time then this is possibly another one.  The loud crack was possibly a point of pressure that built up as one element of the house settled.  Eventually the pressure that built up had to be relieved, thus the cracking sound and the cracked drywall.  Without a physical examination of the premises this is the best explanation I can give at this time. I hope this information helps feel free to write again regarding this or other matters,
sincerely bruce e johnson..bejohnsonconsulting.com