They aren’t what they used to be. A gap of up to 1/8”, and caulked at the joint, was an option in 2001 edition of the James Hardie installation manual, as shown below.

    The current edition of the James Hardie manual, along with the International Residential Code (IRC) and Residential Edition of the Florida Building Code (FBC), offers three options for butt joints:

1. Strip of flashing (water-resistive barrier) under the joint.
2. Caulking at joint.
3. “H” joint cover (like the one shown at top of this page)

    A gap between exposed ends is no longer on the list and only “moderate contact” at exposed butt joints is specified.

Here’s a view of an “H” joint cover from below, which covers a small gap between board ends.

    “Moderate contact” is a term that seems to be intentionally vague, but we suppose it means “touching, but not jammed together.” Occasionally we see homes with moderate contact butt ends that were either not contacting moderately enough, or the movement of the underlying structure caused a compression problem, like the example shown below. In this case it was a siding plank near a corner, which normally sustains more movement.

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To learn more about exterior walls and structures, see these other blog posts:

• Is Hardie fiber-cement siding waterproof?

• What is the average lifespan of a house foundation?

• What causes vertical cracks in fiber cement siding planks?

• What causes raised white lines of residue on a block wall that are crusty and crumbling? 

• What is the difference between soil subsidence, heave, creep, and settlement? 

• How much ventilation is required for the under-floor crawl space of a home? 

• What causes stair-step cracks in a block or brick wall?

• What causes a horizontal crack in a block or brick wall? 

• How can I tell if a diagonal crack in drywall at the corner of a window or door indicates a structural problem?

• What causes the surface of old bricks to erode away into sandy powder? 

• What are the pros and cons of concrete block versus wood frame construction?

• Should I buy a house with a crawl space? 

• Why is my stucco cracking?

• There's cracks running along the home's concrete tie beam. What's wrong? 

• What would cause long horizontal lines of brick mortar to fall out?

• How do I recognize serious structural problems in a house?

• What is engineered wood siding?

• Should I buy a house that has had foundation repair? 

• What is a "continuous load path”?

• Should I buy a house with asbestos siding?   

• How can I tell if cracks in the garage floor are a problem or not? 

• What do you look for when inspecting vinyl siding?

• Why is housewrap installed on exterior walls under the siding? 

• How do I recognize serious structural problems in a house?

• Why did so many concrete block homes collapse in Mexico Beach during Hurricane Michael? 

• How can I tell whether my house foundation problems are caused by a sinkhole or expansive clay soil?

        Visit our EXTERIOR WALLS AND STRUCTURE page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.