correct installation of hard board siding

Have googled and searched nachi forum but have not found a detailed installation procedure, want to be able to inform my client what flashing materials need to be used and to aid the client to know which contractor to hire given these answers and of course the approx cost for repairs.

Just a side note, looks to me that the current rot could be cut out to salvage the upper part of the siding and to allow the installation of flashing materials and so on.
And yep some type of butyl rubber caulk was used in addition to fresh paint on the siding.

My understanding of the proper installation of hard board (glorified cardboard) siding is to leave a 2" gap to top of roof coverings. My real question is are both of these flashings installed:

  • full length down the wall-roof intersection
  • and step flashing on top of the full length flashing
  • can counter flashing be somehow used (this does not seem to be an option for hardboard).

Thanks much for the help.



Suggested fix: cut the siding away at two inches above the roof line and verify if the siding is installed on sheathing or framing. If installed on sheathing step flashing may be used. If installed over framing only, continuous flashing should be used. The bottom of the siding should be primed and sealed to prevent wicking. Keep in mind this is only my opinion, but one based on experience.

If there is rot I modify the comment. If not this is what I use. Obviously cuting would be best, but when the roof or home is 18 years old, then its much easier to seal it unit the roof is repalced.

The siding makes contact with the shingles where it meets the roof. While no wood rot was found there should be a 1" clearance to prevent water from damaging the noted areas. This is something that can be repaired when the roof is replaced or at your convenience. If the issue is not addressed it could become damaged and repair may be needed in the future. Caulk or sealant should help reduce deterioration.

As Mark stated the most crucial thing with “cardboard” siding is The bottom of the siding Must Be Sealed to prevent wicking and deterioration.

try this … Roy

Thanks guys.
All good stuff.
So what’s the best “sealer” that will bond with best adhesion and be an excellent paint primer; obviously these areas being around dormers and wall roof intersections means desiring to fix it once for a long time. Yeah I know the best way to fix is to replace with cement board but this will likely not happen, I know I don’t relish working with hardie panel again anytime soon, great product; just heavy as all get out and not fun to cut either at least as a DIY project.

Thanks again guys.