What is the difference between SPF and SPF south? DF-L and DF-L(N)? HF and HF(N)?

Design values for Spruce-Pine-Fir (SPF) and SPF south (SPF-S) are included in NDS supplement.

SPF is a Canadian species combination graded per National Lumber Grades Authority (NLGA) grade rules. SPF south is the US species combination graded per the following agencies:

Northeastern Lumber Manufacturers Association (NELMA)
Northern Softwood Lumber Bureau (NSLB)
West Coast Lumber Inspection Bureau (WCLIB)
Western Wood Products Association (WWPA)

Similarly, Douglas fir - Larch (DF-L) is produced in the U.S. DF-L (North) or DF-L(N) is produced in Canada. They have different grade marks and different assigned design values. The same holds for Hem-Fir (HF) and HF(N). DF-L will typically be found in western states since it is produced there, while DF-L and DF-L(N) can be found in the Midwest. Note, however, that this is not always true, so the specifier and the contractor need to be in agreement about what is being specified and purchased.