A Guide to Exterior Wall Sheathing

Construction as an industry is continuing to grow in the aftermath of the coronavirus pandemic, in spite of material shortages that have plagued the industry in recent years. Its continued growth makes it a viable contender for a new career path – especially with regard to property construction. But getting started in such an industry requires in-depth knowledge of key techniques and principles. One less-explained technique is that of exterior wall sheathing, a technique that can improve structural integrity and heat efficiency amongst other things. But what exactly is it, and how does it work?

What is Exterior Wall Sheathing?

Sheathing is a critical building process in the construction of new buildings, whether domestic properties or commercial premises. Sheathing is a process wherein materials are used to clad the internal structure of external walls, with different purposes and outcomes depending on the application. 

Often, wall sheathing provides a uniform surface on which to adhere sidings or final external cladding; they are also a useful boundary for the preservation of insulation pockets, and in certain circumstances provided structural rigidity to a build. Exterior wall sheathing can be divided into two key categories: structural, and non-structural. The key distinctions between these two types are further illustrated below.

Structural Sheathing

Structural sheathing is a form of exterior wall sheathing whereby the material used provides fundamental structural support to the building’s framework. This is especially important in cheaper, quicker timber-frame builds; timber studs alone can be weak to lateral and torsional forces, causing the structure to twist and lean. Rigid sheet materials like plywood provide structural rigidity to the studs onto which they are installed, preventing excess movement. Structural sheathing also forms a strong foundation onto which heavier sidings can be installed, without taxing the overall structure too much.

Non-Structural Sheathing

Of course, not all structures require structural sheathing to remain rigid; some stud-based structures may be more rigid by design, while other designs may utilise more rigid base materials such as metal frames. In these instances, sheathing is still desirable for a number of reasons – the first of which is to provide something called the building envelope.

The building envelope is the main barrier between the elements and the interior environment. Building envelopes are more complicated than simple physical protection from the elements, though. For example, thermal envelopes are achieved not with the addition of material but with the creation of an air barrier between outside and inside – the air space in the attic included. Building envelopes are of particular importance in newer projects, owing to their energy efficiency and resultant effect on upkeep costs.

Non-structural sheathing aids in the creation of a building envelope, with different results depending on the material used. Foam boards are a popular choice owing to their insulative properties and uniform surface, while gypsum board can provide an inexpensive waterproof layer in lower-budget builds.