It does not seem like such a good idea to us, but at least one manufacturer we found has a detail for installing the transition between vertical (or, in this case, semi-vertical) vinyl lap siding and horizontal. Here’s the installation detail recommeded by PlyGem.

     Unfortunately, the installation shown in the photo above uses a single J-channel, while the recommended installation diagram specifies two J-channels back-to-back, undersill trim under the lower one, and flashing between them. Here’s a close-up of the transition area, which is definitely less than adequate.

    It’s important to note that vinyl siding is not designed to be waterproof. According to the Vinyl Siding Institute, a national trade organization, “vinyl siding, insulated siding, and polypropylene siding are exterior claddings, not water-resistive barriers, and are designed to allow the material underneath to breathe. This factor provides a supplemental rainscreen that reduces the amount of water that reaches an underlying water-resistive barrier.” But sloppy installation means that more than a little water will get behind the “supplemental rainscreen"—and eventually cause a problem. 

    Also, see our blog posts What do you look for when inspecting vinyl siding? and Can vinyl siding be painted? 

• • • • • • • • • • • • • • • • • • • • • • • • 

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

• 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 structural problems in a retaining wall? 

• 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 if the concrete block walls of my house have vertical steel and concrete reinforcement?

• Should I buy a house with structural problems? 

• What are those powdery white areas on my brick walls?

• What causes cracks in the walls and floors of a house?

• How can I tell if the exterior walls of a house are concrete block (CBS) or wood or brick?

• What are the common problems of different types of house foundations? 

• What are the warning signs of a dangerous deck?

    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. 

Photos - Ben Michler, Diagram - PlyGem