Deck Stair Treads

[Gary M]

The International Residential Code (IRC) in the footnote (c) in Table R301.5 specifically calls for 300 lb concentrated load compliance at stair treads, which thus far in my investigation, treated 5/4 x 6" deck boards fail to perform on 18" centers. The IRC also calls for a max 1 1/4” nosing, which means 2x nominal lumber is not compliant as a tread with closed risers, either.

This is an odd code compliance dilemma for the treated wood products at deck stairs.

Are you aware that anyone proved 5/4 treated deck boards meet this 300 lb. concentrated live load criteria?

 

[MtnArch]

Use the 2x material and provide flush nosing.

 

[Francis Vineyard]

R301.7 Deflection. The allowable deflection of any structural member under the live load listed in Sections R301.5 and R301.6 or wind loads determined by Section R301.2.1 shall not exceed the values in Table R301.7.

Allowable deflection L/240?
Below illustration from the AWC DCA6-12

 

[SCBO1]

Footnotes R301.5 - 40LL* c. 300-pound concentrated load acting over an area 4 square inches which ever produces the greater stresses.

 

[jwilly3879]

1 1/4" nosing is the projection beyond the closed riser.