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  Durable Exterior Trim: Equilibrium Moisture Content  
 
 

Moisture Content vs Relative Humidity

Relative Humidity
Moisture Content
0
0
25
5
50
9
75
14
80
15-16
90
20-21

*Taken from: Understanding Wood, by Bruce Hoadley;
calculated at 70 degrees F

For Flat-grain Softwood: every 4% change in MC = approx. 1% Change in Size
 
Shrinkage Values of some Oregon wood species based on their dimensions when green          
(values are in percentages)        
 
Dried to 20% MC
Dried to 6% MC
Species Radial
Tangential
Radial
Tangential
Incense Cedar
1.1
1.7
2.6
4.2
Port-Orford Cedar
1.5
2.3
3.7
5.5
Western Red Cedar
0.8
1.7
1.9
4.0
Douglas Fir (coast)
1.6
2.5
3.8
6.1
Western Hemlock
1.4
2.6
3.4
6.2
Ponderosa Pine
1.3
2.1
3.1
5.0
Redwood (Old Growth)
0.9
1.5
2.1
3.5
Redwood (Second Growth)
0.7
1.6
1.8
3.9
         
From Wood and Moisture Relationships by J.E. Reeb; EM 8600, June 1995        
         
         
         
 
 
 
 
 
 
     
     
   
     
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