Home » Framing » Structural Wall Sheathing

It is important to be aware of proper wall framing basics because the walls of your small house will bear the load from the roof down to the foundation and act as the protector against the elements of changing weather for many years to come. Basic carpentry framing for the walls must be accomplished with future projects in mind such as drywall and kitchen cabinet installation. If the walls are not constructed properly it will make these future projects difficult to achieve.

If you live in an area that is subjected to high-velocity winds or is rocked by frequent earthquakes then you should pay special heed to the exterior walls of your house. These walls now need to not only repel moisture as any other house but also need to withstand nature’s fury when it is being pounded by rain and high winds or being rocked by an earthquake. Structural wall sheathing is a product that not only imparts structural rigidity to your house but also ensures that it has the strength to support siding materials that will be attached to it in due course.

The sheathing itself can be done using various materials such as plywood, external gypsum board, oriented strandboard or OSB, wafer-board, steel or even synthetic resin-based panels. In fact there are some sheathing materials that have managed to combine both strength and insulation to save on time and labor.

A stack of exterior plywood with tongue-and-groove edging.

Half inch thickness plywood or any other material is ideal for structural sheathing since the vagaries of nature might otherwise simply peel off the sheet and throw it in the air like a feather. While most exterior sheathing is done after the frame has been built, there are also people that use pre-fabrication processes to get an entire wall ready before tilting it into position.

Once the external sheathing is done, it is very important to ensure that it is covered with house wrap to protect it from rotting due to moisture. One of the biggest enemies that attack walls is water as it leads to rotting or the development of mold. Moisture can attack the wall from outside and inside and hence it is necessary that you take steps to protect your walls from both ends with the use of sealants. Felt paper or housewrap will also be required to be installed perfectly to prevent chronic moisture infestation.

A handy illustration from This Old House on how to use a rope to help carry a single sheet of plywood. There are also special handles, in plastic or metal, to help extend your arm to hold the bottom of a panel in a similar way. These are examples of “working smarter”,
not harder!

If you are using plywood then remember to choose the correct grade and ensure that the higher grade is facing towards the outside of your house. Other materials need to be chosen only as per their designated roles (ie. graded for exterior use).

You should also ensure that you have a 1/16 inch gap between two consecutive panels and 1/8 inch gap between the edges of your panels depending on the material that you use. This ensures both a way for the wall to “breathe” a little and a bit of expansion space during seasonal fluctuations in temperature and humidity.

You will also need to use galvanized nails at approved distances to attain the level of rigidity based on the local climate. Additional bracing should be provided if your neighborhood is prone to attacks from hurricanes or tornadoes. If you are using structural sheathing with inbuilt insulation then you will also need to meet fire-code regulations before you affix them on your house. Inspection by the building inspector will ensure that your sheathing is properly installed and remains in the best of health and keeps you and your loved ones safely cocooned at all times.

Oriented strand board, or OSB, is composed of large flakes of wood essentially glued and pressed together. The big disadvantage to OSB, I feel, is it’s fantastic ability to absorb water. If exposed to rain for even a short amount of time it’s as good as garbage. Maybe future development of the product will try and improve
on this.

Check your local building codes to find out if type and spacing of nails or screws is specified There’s usually a good reason that the codes specify a certain product used in a certain way. It’s usually because somebody in the past learned the hard way.

Structural wall sheathing is an integral process in the construction of any house, especially if it is subjected to bad weather or earthquakes. Care should be taken to use the right material for sheathing and to follow building codes to perfection. Regular maintenance and checkups will ensure that your sheathing lasts longer and does the job for which it was installed in the first place. Instead of only thinking about lowering your costs while sheathing your walls, think about the safety factor first and spend a little more if need be to ensure complete external and internal protection for a very long time.