30 Jul What Are the Different Types of Exterior Wall Sheathing Materials and Their Uses
Table of Contents
Builders use a few main types of exterior wall sheathing. These include plywood, oriented strand board (OSB), fiberboard, ZIP System panels, and magnesium oxide boards. Each exterior sheathing material has its own good and bad points. Knowing the difference between structural and non-structural choices helps people make better decisions. Important things like strength, moisture resistance, insulation, fire resistance, and cost all matter when picking the best exterior wall sheathing for a job.
The table below shows some of the most common exterior sheathing types and what they are used for:
Sheathing Type | Examples | Key Use |
|---|---|---|
Structural | OSB, Plywood, Gypsum | Strength, rigidity, nailing base |
Non-Structural | Fiber Board, Foam Board | Insulation, increased R-value |
Key Takeaways
Exterior wall sheathing makes buildings stronger. It also keeps out wind, rain, and moisture. – Structural sheathing like plywood and OSB holds up the building. It also makes it last longer. Non-structural sheathing like fiberboard helps keep heat in. – Plywood is good for wet places if you seal it well. OSB costs less but must be kept dry. – Some sheathing, like ZIP System panels, helps build faster. They also stop air and water from getting in. Magnesium oxide boards are very strong against fire and water. – You should pick sheathing based on weather, money, and what the building needs. Checking and sealing sheathing often helps it last longer.
Exterior Wall Sheathing Overview
Purpose and Functions
Exterior wall sheathing is very important in building today. Builders put it on the outside of a building’s frame before siding goes on. This layer makes the building stronger. It also helps protect the building from wind and rain.
Structural exterior wall sheathing makes the building strong and stiff. It gives a good base for siding and keeps the frame safe from weather.
Non-structural exterior wall sheathing adds insulation. It can also help block heat from the sun. This type helps save energy by keeping heat in and stopping moisture.
Sheathing membranes go outside the structural layer. They control how water and air move. These membranes help keep the building sealed and dry.
Exterior sheathing helps the building stand up to wind and earthquakes. It blocks water, air, and moisture from getting inside. Some types add insulation, so the building stays warm and comfortable.
Tip: Pick a moisture resistant exterior wall sheathing. This can help stop water damage and mold.
Structural vs. Non-Structural
The main difference is if the sheathing can hold up weight or not.
Aspect | Structural Exterior Wall Sheathing | Non-Structural Exterior Wall Sheathing |
|---|---|---|
Load-Bearing Capacity | Holds up building weight (over 100 pounds per foot) | Only holds its own weight |
Code Definition | Part of the building’s main frame | Not part of the main frame |
Fire-Resistance Rating | Needs higher fire resistance (2-hour rating) | Needs lower fire resistance (1-hour rating) |
Application | Used where walls hold up floors or roofs | Used for insulation or as extra walls |
Construction Cost | Costs more because it is stronger and safer | Costs less and is simpler |
Structural exterior wall sheathing, like plywood or OSB, makes the building strong. It helps the building stay up during wind and earthquakes. Non-structural exterior wall sheathing, like fiberboard or foam board, does not hold up the building. It adds insulation and saves energy. Builders pick the right type based on what the wall needs to do and the local rules.
Exterior Wall Sheathing Types
Plywood
Plywood is a common choice for structural exterior wall sheathing. To make plywood, thin wood layers are peeled from logs. These layers are stacked with the grain going in different ways. Glue holds the layers together with heat and pressure. This makes plywood strong and stable. It does not change much with weather. Most exterior plywood uses softwood like pine, fir, or cedar. These woods are strong and not too expensive.
Builders pick plywood because it lasts a long time. It is a good base for siding. It also supports walls, roofs, and floors well. Plywood does not bend or split as easily as some other materials. In wet places, like corners or cut edges, plywood works better than OSB. It stays strong and keeps out water better.
Tip: Seal the edges and surfaces of plywood. This keeps water out and helps it last longer.
Aspect | Advantages | Disadvantages | Climate Considerations |
|---|---|---|---|
Strong, lasts long, keeps out water better than OSB, light, can be used in many ways | Costs more than OSB, can soak up water if not sealed, sun can damage it | Use marine or pressure-treated plywood in wet places; use CDX or exterior plywood in dry places and seal it | |
Moisture Resistance | Better than OSB; special plywood works best in wet places | Can bend or come apart if not sealed | Always seal edges and surfaces; check and fix often |
Aesthetic Qualities | Smooth look, can be changed to fit needs | Not as tough as marine plywood | Good for looks in places that are not too wet |
Installation & Maintenance | Easy to use and put in, sealing helps it last | If you do not seal it, it gets worse faster | Check and seal it often |
Plywood is best in places where there is a lot of moisture. It works well if you seal it right. Builders use it for structural exterior wall sheathing in homes and businesses.
Oriented Strand Board (OSB)
Oriented Strand Board, or OSB, is another wood-based structural sheathing. OSB is made by pressing wood strands together with glue. The strands are lined up in certain ways to make it strong. OSB comes in different thicknesses, from about half an inch to one inch.
OSB is strong and works well for walls that hold weight. Builders use OSB for exterior wall sheathing, floors, and roofs. It is a good base for siding and other finishes. OSB is heavier than plywood but costs less. This makes it good for saving money.
Feature | OSB | Plywood |
|---|---|---|
Strong for holding weight | Stiffer and better at taking hits | |
Moisture Resistance | Soaks up water, edges can swell, dries slowly | Keeps out water better, dries fast, stays stable |
Fastener Retention | Nails and screws do not hold as well | Nails and screws hold very well |
Cost | Cheaper by 15–30% | Costs more |
Weight | Heavier | Lighter |
OSB is best in dry places or when you need to save money. But it soaks up water more than plywood, especially at the edges. This can make it swell and get damaged over time. Builders should use water-resistant coatings and install it right to protect OSB in wet places.
Note: OSB is not the best for places with lots of rain or high humidity unless you treat and install it carefully.
Structural Fiberboard
Structural fiberboard is a non-structural exterior wall sheathing. It is made from wood fibers, glue, and wax. How strong it is depends on the type, like particle board, MDF, or HDF. Fiberboard keeps heat in better than OSB. It has an R-value of about 1.3 for every half inch. This makes it good for insulation.
Fiberboard does not change shape much and lets water vapor pass through. This helps stop water from getting trapped in walls. But it is not as strong as OSB or plywood. It may need extra support for some jobs. Fiberboard can crack or get worse if it gets wet, so sealing and care are important.
Pros:
Gives good insulation and saves energy.
Stays the same size and shape.
Lets water vapor out, so less moisture builds up.
Cons:
Not super tough; can crack or get moldy if not sealed.
Heavier and harder to move.
Not as strong as wood-based structural sheathing; needs more support.
Fiberboard is good as non-structural exterior wall sheathing in mild places. It is also used with foam sheathing to add more insulation.
ZIP System Sheathing
ZIP System sheathing is a special wood panel. It has structural sheathing and a water barrier built in. This means you do not need housewrap. When builders tape the seams, the wall blocks air and water.
Key features include:
Built-in water and air barrier.
Strong enough for walls that hold weight.
Can have insulation for saving energy.
Nail lines printed on the panel for easy use.
ZIP System sheathing makes building faster. It cuts down on steps and work. It protects from weather right away, so inside work can start sooner. The panels do not soak up water or bend easily. Taped seams stop leaks. The system works in high-wind areas and has a 30-year warranty.
Tip: ZIP System sheathing is great for fast jobs and saving energy, especially where weather changes a lot.
Builders use ZIP System panels in new homes and businesses. The system can be used for both structural exterior wall sheathing and non-structural jobs, depending on how it is put together.
MgO Wall Sheathing
Magnesium oxide (MgO) wall sheathing is a cement board structural sheathing. It is made from magnesium oxide, magnesium chloride, perlite, wood fiber, vermiculite, and glass mesh. This mix makes MgO boards very strong and fireproof. They also keep out water very well.
Component | Role/Property Description |
|---|---|
Magnesium Oxide | Makes it fireproof and strong. |
Magnesium Chloride | Holds the board together. |
Perlite | Adds insulation. |
Wood Fiber | Makes it stronger and more flexible. |
Vermiculite | Helps with fire resistance. |
Glass Mesh | Makes it tougher. |
MgO boards can take fire for up to four hours without getting weak. They block water, mold, and mildew. This makes them good for wet or humid places. MgO sheathing is also good for the environment.
Pros:
Great at stopping fire and water.
Very tough and hard to break.
Lasts a long time in damp places.
Good for green building.
Cons:
Costs more at first than OSB or plywood.
Can break and is hard to cut.
Nails do not hold as well; may need special fasteners.
Not easy to find everywhere.
MgO wall sheathing is best in places with lots of fire or water risk. Builders should keep MgO boards dry for a long time and install them right to stop cracks.
Other Sheathing Types
Some jobs use gypsum based structural sheathing or rigid foam sheathing for special needs. Gypsum based structural sheathing stops fire and is used in many business buildings. Rigid foam sheathing gives high insulation and is often used as non-structural exterior wall sheathing or in EIFS. EIFS, or exterior insulation and finish systems, mix insulation with a nice finish. This makes buildings save energy and look better. Builders use EIFS for new buildings or to add insulation and keep out water.
Note: Always pick the right sheathing for your weather, building rules, and project needs to get the best results.
Exterior Sheathing Comparison
Strength and Durability
Tests show magnesium oxide boards are the toughest. They do not bend, swell, or crack in bad weather. Plywood and OSB are strong if they stay dry. Fiberboard keeps heat in but can break when put in. ZIP System panels mix strong wood with a water barrier. This makes them tough and dependable. The table below shows how these materials compare:
Material | Durability and Strength Characteristics | Insulation (R-value per inch) |
|---|---|---|
Magnesium Oxide | Extremely durable; resists mold, mildew, insects, warping, swelling, and cracking | N/A |
Fiberboard | Eco-friendly; superior insulation (R-2.5); less durable; prone to moisture damage | 2.5 |
OSB | Cost-effective; strong in dry conditions; weakens with moisture | 0.5 to 0.62 |
Plywood | Balanced performance; moderate durability; similar insulation to OSB | 0.5 to 0.62 |
ZIP System | Strong with integrated water resistance; enhances energy efficiency | N/A |
Moisture and Weather Resistance
Water can cause big problems for exterior sheathing. OSB and plywood need sealing to stop swelling and rot. MgO boards and ZIP System panels block water and mold very well. Fiberboard can soak up water and fall apart if not protected. Builders use plywood in wet places because it stays steady. Rigid foam sheathing and glass mat gypsum also block water and mold. These are good for rainy places.
Water can get in at roof edges, windows, or where siding meets.
Trapped water causes rot and damage, mostly in OSB and wood.
MgO and ZIP System help stop these problems.
Insulation and Energy Efficiency
Insulating sheathing helps keep buildings warm or cool. Fiberboard and rigid foam sheathing give the best insulation. ZIP System panels also help by stopping air leaks. Plywood and OSB give some insulation but not as much as foam or fiberboard. Adding more insulation, like EIFS or rigid foam, helps save energy and money. This keeps rooms comfy and lowers bills.
Fire Resistance
Fire safety is very important. MgO boards and gypsum sheathing protect well from fire. Plywood and OSB burn faster, so builders use special treatments in fire zones. Fiber cement and EIFS with mineral wool also fight fire well. The chart below shows fire ratings for common wall types:
Cost Considerations
OSB costs the least, so it is good for cheap projects. Plywood costs more but lasts longer in wet places. MgO boards cost more at first but save money later because they last. ZIP System panels cost the most but save time and work. Rigid foam sheathing and EIFS cost more at first but help save energy and make buildings comfy.
Material | |
|---|---|
Magnesium Oxide | $1.50 to $3.50 |
OSB | Cheapest |
Plywood | More than OSB |
ZIP System | Most expensive |
Tip: Builders should pick sheathing that fits the weather, job, and budget. EIFS and rigid foam sheathing are best for saving energy. MgO and gypsum are best for fire safety.
Builders and homeowners have choices like plywood, OSB, fiberboard, ZIP System, and MgO boards. Each one is good for certain weather and money plans.
Experts say to make sure the building is airtight and keeps out water.
You should also put the panels in the right way.
Some places with strong winds need thicker panels or special fasteners.
Checking and sealing the sheathing often helps it last longer.
To get the best outcome, look at all your choices and ask a building expert before you decide.
FAQ
What is the main purpose of exterior wall sheathing?
Exterior wall sheathing gives strength to walls. It helps keep out wind and rain. Builders use it as a base for siding. Some types also add insulation.
Which sheathing material works best in wet climates?
Plywood and magnesium oxide (MgO) boards work well in wet climates. Plywood resists water when sealed. MgO boards block water, mold, and mildew. ZIP System panels also protect against moisture.
Can you use foam board as structural sheathing?
No, foam board does not support building weight. Builders use foam board for insulation only. It works with structural sheathing like plywood or OSB.
How often should exterior wall sheathing be inspected?
Builders should check exterior wall sheathing once a year. Look for signs of water damage, mold, or cracks. Early repairs help keep the building safe.