Expert: Bruce E. Johnson - 12/4/2008

Question
QUESTION: Hello Bruce --

I live in a house in Charlotte, NC that was built in 1983.  It is built over an open air crawl space which is very common for homes in North Carolina.  While we have lived in this house for five years, over the past two months the drywall walls and ceilings in several areas throughout the house have started to buckle slightly.  There appears to be a new buckle every few days.  There have also been several new nail pops that have started to appear -- mainly in the upstairs rooms.  This is happening both upstairs and downstairs.  I have had two crawlspace specialist check out the crawl space/foundation and both determined that everything is structurally sound and it does not appear to be structural in nature.  This confirms the structural inspection we had when we moved into the house in 2003.

Since the two specialist confirmed the structure and crawl space check out, I am trying to determine what could be causing this buckling in the walls and ceilings.  Since we have been in the house for five years and this is the first time this is happening, I am trying to isolate what could be causing it so we can properly address the situation.  Since it is a combination of both buckling and nail popping, I am trying to determine what I can do to remedy the situation.    

Please let me know your thoughts.  Thanks for your help!

ANSWER: Hi Jason, gosh that's a puzzler.  No evidence of settling in the foundation?  Okay then.  There could be a couple of areas to investigate.  One would be the horizontal shear of your wall framing.  Have you had some severe wind events preceding the recent damage?  Wind shear may cause a framed structure to shift back and forth if the walls are not properly braced.  This would  cause the drywall to pop and buckle but it would also show up around the windows and doors showing separation in these areas.

Moisture could be a culprit.  Drywall will expand when wet and then contract again when dry this could cause nail pops.  If damp drywall is left to dry it will assume the shape it was in when wet, i.e. waviness, buckling.

Extreme temperature conditions may cause the house itself to expand and contract abnormally.  If it is very hot one day and the exterior walls get hot and then that night a cold front comes through dropping temperatures forty or fifty degrees can cause the wood framing to contract faster than the drywall.

If you left the house open a lot during the fall and the humidity was high and then closed the place up and turned on the heater suddenly this could cause the walls to react to the sudden change in temperature and humidity.  Normal humidity in a dwelling should be around 50% and temperatures should be kept within 10-20 degrees of each other at the high and low points of the seasons, i.e. mid seventies summer, mid sixties winter.  

If there has been any construction nearby like roadwork where vibratory equipment is used or blasting in nearby mountains that cause your walls to vibrate this could cause problems as well.

I guess I've thrown enough stuff against the wall, does any of it make specific sense?  Feel free to write again regarding this or other matters, sincerely bruce e johnson..bejohnsonconsulting.com

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

QUESTION: Hi Bruce

Thanks for the quick response.  Since the weather was mild this fall, we did open the windows in the morning for fresh air.  In terms of humidity overall, while Charlotte is normally humid in the summer -- our house is extremely dry in the winter and somewhat humid in the summer.  I am wondering if that could be causing some of this buckling and popping based on your comments above??  Since it is effecting multiple rooms throughout the house?

The other thought I wanted to ask your opinion if you think the expanding and contracting of the roof (due to weather, etc.) could be impacting the drywall and nail popping?  We have a standard shingled roof and I wasn't certain if that could be having an impact on this as well.  Would welcome your thoughts.

Jason

Answer
Hi again Jason, the roof may affect your walls but for a different reason.  The roof structure takes the most wind shear because of the size and the height.  If the roof system isn't properly braced and tied down then yes it could put the walls under undo strain.  I don't know.  Is there anything else you can think of?  Get any hurricanes this summer or strong tropical force winds?  What about the recent systems that have moved through the south east?  

bruce e johnson