Reviewing the James Hardie Hardieplank installation instructions shows that this detail is not addresses specifically, however, there is a detail which addresses 'similar' points of installation, that being "Clearances" "Maintain a minimum 2" clearance between James Hardie products and decks, paths, steps and driveways." "Figure 4".

Figure 4 shows that 2" clearance to both the horizontal surface and the vertical surface on steps (i.e., treads AND risers).

The riser (vertical) portion would be 'similar' to the vertical chimney, so, *in my opinion*, a trim should be installed between the Hardieplank and the chimney.

Or, send the photo and an e-mail to James Hardie and get the answer from the horses mouth.

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Jerry Peck, Construction / Litigation Consultant
Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )