Stucco Sheathing

osb sheathing

Sheathing is basically the “backing material” that can be found underneath the various layers of stucco that form the backing of residential and commercial buildings.

They can be made out of wood, cement, gypsum, fiberglass and other materials. Let’s take a deeper look at these different sheathing materials to get a better understanding of each of them.

​Wood Sheathing:

This is the most common type of sheathing found on most residential applications these days and can come in two different forms:

​OSB:

Short for (orientated strand board) is a man-made product that is constructed using adhesives and flakes of wood that are compressed in multiple layers. This is an inexpensive product and is what most residential and commercial builds use, when wooden sheathing requirements are needed.

  • Is usually around 3/8″-5/8″ thick for most stucco applications (unless noted by building plans, or county/state requirements)
  • Can be found at most large home improvement stores and is readily available
  • One of the cheapest sheathing options out there
  • Comes in 4′ by 8′ sheets typically
  • Additional links for OSB:
    1. Wikipedia
    2. HowStuffWorks.com

​Plywood:

Is layers of thinner “veneer like” ply-woods that are glued together, alternating the grain of the wood that form a single solid sheet. Ply wood is more expensive than OSB, but repels water a little bit better and provides a bit more strength too.

  • Is usually around 3/8″-5/8″ thick for most stucco applications (unless noted by building plans, or county/state requirements)
  • Can be found at most large home improvement stores and is readily available
  • Moderately priced, but still competitive
  • Comes in 4′ by 8′ sheets typically
  • Helpful links on plywood:
    1. Wikipedia
    2. HowStuffWorks.com

​Additional Notes: When using wood substrates, you should space the sheets about 1/8″ to allow for expansion if the sheets happen to get wet. If you do not, then the sheets could potentially buckle and create cracking issues in the base coat(s) and/or finish coat of the stucco.If installing new wooden substrate, you can use 16d nails to create an 1/8 of an inch gap on all plywood/OSB sheathing. If already installed with no gaps included, a skillsaw or router can be used to create the gaps by cutting down where the sheets meet. Only gap if the manufacturer requires it, if not, follow their directions for proper installation.

When using wood substrates, you should space the sheets about 1/8″ to allow for expansion if the sheets happen to get wet. If you do not, then the sheets could potentially buckle and create cracking issues in the base coat(s) and/or finish coat of the stucco.If installing new wooden substrate, you can use 16d nails to create an 1/8 of an inch gap on all plywood/OSB sheathing. If already installed with no gaps included, a skillsaw or router can be used to create the gaps by cutting down where the sheets meet. Only gap if the manufacturer requires it, if not, follow their directions for proper installation.

​Exterior Gypsum Sheathing

This is basically an exterior grade drywall that is more commonly found in commercial projects, but can also be found in some residential applications as well. It has additive mixed into the base of it, which make it water-resistant and is coated with a water-resistant paper material as well.

  • Is usually found in 1/2″ – 5/8″ thick and comes in a 4′ by 8′ sheet, typically, but can also be found in 10 and 12′ lengths as well
  • Is more of a specialty item and is not typically found anywhere and everywhere
  • Is moderately priced
  • Make the installation process much faster, so it’s easier to achieve deadlines
  • More typical in commercial applications
  • A couple of related links:
    1. ASTM.org & ASTM.org
    2. Gypsum.org
  • Manufacturers of exterior gypsum and their websites:
    1. Georgia Pacific (Densglass)
    2. National Gypsum
    3. CertainTeed
    4. American Gypsum

​Glass Mat Sheathing

Similar to exterior gypsum board, but uses a fiberglass barrier instead of a paper product on the outside.

  • Similar sizes to exterior gypsum
  • Is also a specialty item, but is usually found at most stucco supply yards or can be ordered
  • Is a bit pricey
  • More common in commercial applications
  • Helpful Links:
    1. ​Coming Soon!
  • Manufacturers of glass mat sheathing and their websites:
    1. Georgia Pacific (Densglass)
    2. USG
    3. CertainTeed
    4. National Gypsum

​Additional notes for gypsum and glass mat sheathing:

  • Both can be cut using a utility knife, just like you would if you were cutting interior drywall
  • Glass mat sheathing has fiberglass on the outer layers, which can irritate the skin, eyes and other parts of the body, so take the necessary precautions when handling or applying the material
  • They both are typically available in 1/2″ and 5/8″ thickness
  • They both carry a fire rating, which can help if building within close quarters of another structure (check manufacturer’s specs)

​Cement Board

Cement board is basically a mixture of cement and reinforcing fibers (fiberglass strands) that is formed into a sheet that can be attached to a wall easily, providing a great base for tile or other masonry products.

Resources For This Article:

About the author

The Stucco Guy

My name is Ryan and I have been in the construction trades for many years now and I feel that there is a huge "knowledge gap" when it comes to particular trades.... like stucco.

I hope you find the information here useful and if you have a question that requires a more in depth answer, then please check out my consultation gig. Thanks for stopping by!

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