Ship Lap

What is Ship Lap?

Definition of Ship Lap in Construction

Type of siding that overlaps each adjacent piece by a predetermined amount. The siding is created in such a way that there are overlapping tongues of material that will cause the installation to be waterproof. Ship lap is a common type siding, made of wood, vinyl or other synthetic products. This type of siding, together with the board and batten, was extremely common in colonial times, and is still used extensively. Ship lap is relative inexpensive and easily installed.

If the product is made of untreated wood, it is recommended that the material be treated prior to installation. The treatment of any type of untreated siding, prior to installation, insures that the product, both front and back, has been at least primed, if not finished treated. In many instances the installation of a ship lap siding is associated with a full building wrap, to further ensure water tightness and proper vapor barrier placement. Ship lap siding has been used for centuries, it is a common, easy and inexpensive method for securing water protection and providing a pleasant exterior appearance.

Thoughts on the Evolution of the Term

Like so many other construction terms emanating from the DIY social media hysteria, the term shiplap has become a common “go to“ word, as the latest crowd of self proclaimed professionals discuss their exploits.

The word has now evolved into a primary focus for large home suppliers, such as Home Depot and Lowe’s to devote aisles of product focused on selling this extraordinary product to the latest group of house renovators.

The term, shiplap, was probably never actually used to describe the profile of the wood planks that were used in old ship building days to waterproof their vessels.

I can remember our old 12 foot fishing boat when I was a kid, and how we had to get it in the water and bail until the wood swelled and sealed the hull. Well guess what? This swelling of wood planks was in today’s modern terminology, shiplap, the swelling of the joints between boards, or the shiplap joints of the hull. Ship builders were very savvy and skillful individuals, and they did not have the sophistication of a google search engine or the insight of academia to instruct them in regard to how to make this planking more efficient and watertight. Skilled craftsmen, trying to create a better and more watertight ship or boat used various techniques to increase the ability of the boards to seal themselves. The final result was the rabbetting of each of the boards edges to create an overlap of wood at the joints. This overlap of the wood allowed the swelling of these thinner rabbets to seal against one another, as the wood swelled.

If contemporary home improvement gurus want to call this type of wood paneling application shiplap, it does make sense, however I have a feeling that the professional shipbuilders of the time merely knew how to make hulls watertight. This rabbet joint worked the most efficiently, however these craftsmen did not have the social media world to identify their level of skill and workmanship.

Any type of planking or interaction of wood elements that is allowed to sit in water and swell will eventually tighten up. The interface of two opposite rabbetts, maximizes the swelling of this joint, and therefore maximizes the watertightness of the end product.

Shiplap is certainly a practical and accurate identification, however let’s not forget the shipbuilder’s professional skill and ingenuity that led to this identification.

The importance of the watertightness of a wood vessel in the middle of the Atlantic is certainly much more impressive than the paneling of the kitchen within a “ Flip”.