There has been much discussion among designers and craftspeople, within the blogosphere and elsewhere, about whether what today gets called shiplap is actually shiplap. By definition, shiplap consists of boards that are joined in an overlapping manner via a rabbet, which is a recess that forms the joint between the boards. In shiplap, the overlapping manner of the boards and style of the rabbet leave a small space between each board, although they are edge to edge in order to be watertight in the back.
The gap is about the width of a nickel, so sometimes "nickel slot" can be used to describe shiplap. Real shiplap does have a joint, but it's not a tongue and groove situation. The rabbet joint is stacked rather than inserted. Shiplap is nailed directly to the surface, leaving nails visible, which is appropriate for the material's rustic appearance.
When it was initially used in home construction, shiplap was not meant to be exposed, according to the Durasupreme Cabinetry blog. It provided a shield between the exterior and the framing and was covered with a cheap fabric, then wallpaper. Shiplap's location behind the visible wall is the reason Joanna sometimes discovers it during demo.
In a blog post, she explained how she found it in her family's farmhouse residence: "It was during the first few days of demo that we discovered shiplap in nearly every space of this house. I had spotted this material before in other projects and was immediately drawn to its timeless style and organic texture. ... The more shiplap we found around the farmhouse, the more I knew that I wanted to expose it throughout our home."
Her appreciation for the rustic stuff appeared in many of her renovation projects, and if there was none present, it could be added. Thus, shiplap became a design feature that was used to accent space and not only uncovered but applied. Chip has a video explaining how to make shiplap, and he details that when he finds a piece of shiplap – a rough, old plank – he removes the nails, gets rid of any splinters and voila! It's still rough looking, but that is the way Jo likes it.
However, unless Chip's boards have a rabbet joint, they are not true shiplap, they are just old boards that are going to be applied to the wall or piece of furniture, as Scott Sidler explained in The Craftsman Blog.
Does it matter to the average fan of farmhouse style?
"There are different styles of how it attaches together," says Mike Cheatham, owner of Movable Roots custom tiny home builders. "But the end look of it from the outside pretty much all looks the same."
Homeowners seeking to incorporate a shiplap look might be less concerned with the facts about shiplap and more interested in its visual effect. For example, Jenna Sue Design Co. provides a DIY Shiplap Tutorial video where she shows viewers how to use plywood and nickels to create easy and inexpensive "shiplap" walls. Shiplap typically ranges in price anywhere between $2.50 and $7.00 per square foot for real wood boards.