Q: What is the proper humidity for an office?

A. Your short question makes me think that you made some cabinets, shelves or furniture for an office and now you have experienced some quality issues and want to blame the low humidity in the office for the problems.
 
 

KNOWLEDGE CENTER

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Gene Wengert, aka The Wood Doctor, troubleshoots wood related problems, and explores lumber and veneer qualities and performance, species by species, in Wood Explorer, inside FDMC's Knowledge Center.


A typical air-conditioned office in the summertime will have humidity around 50 percent RH, which means about 8-1/2 percent to 9.0 percent MC in the wood. (A finish on the wood slows moisture movement but does not prevent it. Likewise, kiln drying does not stop the change in MC when the humidity changes.
 
In the wintertime, the typical office that is heated will develop average humidities around 30 percent RH, or even drier in cold climates. Most offices do not have control of the humidity, so they tend to be quite dry in the wintertime. In homes, we have moisture added from house plants, bathroom showers, and cooking, plus we might have a humidifier, but most offices do not have such moisture additions. So, we can expect the wood in an office in the wintertime to reach about 6.0 percent MC or a bit drier in colder climates.
 
 
 
Because wood begins to warp, low quality glue joints begin to open, and small pre-existing cracks can reopen when wood dries over 2 percent MC when in use, we will tend to make most office furniture at around 6.8 percent MC to avoid any excessive drying. This level in the summer does mean a little moisture regain, but the gain is small enough to avoid most problems.
 
So, my questions to you are, “What moisture content was the wood when you made the wood products?“ and “Did you check the moisture content or did you rely on the suppliers stated values?”
 
A good moisture meter (over $200) that is used to monitor the incoming lumber and also the products when you ship them can assure you that any moisture related problems by the consumer are the shipper’s or the consumer’s mishandling (assuming your moisture checks were at appropriate values). Without these moisture values, you “are on thin ice.”

 

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