HardiePlank is a popular exterior cladding because it seems like it would be impossible to destroy. The cementitious product seems impervious to water related failure and rot. And while many dismiss issues with HardiePlank, the durable layered siding is prone to the same moisture entry issues as every other layered siding. For installation guidelines we have to look to the details in the HardiePlank installation specs.
Fellow inspector, Dan O’Rourke from Oklahoma City, Oklahoma asked, “How important is it to recommend L-flashing behind the siding and then on top of the first row planks to prevent water from deteriorating the bottom course of HardiePlank?”
The photo below shows the installation in question where they installed the deck after the initial construction. You can clearly see that the deck ledger was slapped right over the HardiePlank siding.
To find the answer to Dan’s question we must turn to the manufacturer for guidance. The manufacturer’s installation specs trump all other requirements because they have developed, produced, and tested their product to perform to specific installation guidelines. While you look at the HardiePlank specs below, ask yourself the following question... “Do we really think that JamesHardie wants any liability with deck failures?” The answer is a firm “No”, and the manufacturer does everything they can to stay completely away from being named an integral party to the deck failure liability loop.
In Figure 4 above, the manufacturer’s specs are clear to state that a 2” clearance is needed from decks. Personally, I love it when they show diagram pictures that are so clear that even a child with no building experience can see the pictures and understand. JamesHardie is also clear to show the type of flashing needed that allows their product to stop above the deck ledger. This flashing helps get the moisture that migrates behind the HardiePlank out and over the ledger so that they will not be liable for deck failures due to rotted deck ledger boards. And if that isn’t enough, please read their first disclaimer in their specs again.
HardiePlank is a popular exterior cladding because it seems like it would be impossible to destroy. The cementitious product seems impervious to water related failure and rot. And while many dismiss issues with HardiePlank, the durable layered siding is prone to the same moisture entry issues as every other layered siding. For installation guidelines we have to look to the details in the HardiePlank installation specs.
