Updated at: 15-06-2022 - By: Sienna Lewis

How long does OSB board need to dry before it can be used as a sheathing for water-damaged walls? Too much time left in the dampness can lead to decay and mold growth, neither of which you want within your house.

One of the most versatile materials on the market is Oriented Strand Board (OSB). It can be used for everything from flooring and wall sheathing to roofing and even furniture. Although this substance is water-resistant, it is nevertheless subject to rot, just like wood is. In order to assist you, we’ve listed numerous things you may do for your OSB boards to help you get through this predicament.

What Happens When An OSB Board Get Soaked

The primary purpose of these engineered wood planks is to tolerate the constant presence of water in the residence. Even so, they should not be exposed to excessive amounts of water.

4 Factors On How Long To Dry OSB Board In Water Damaged Wall - Krostrade

When frequently exposed to damp and dry conditions, OSB degrades more quickly than other wood products. That’s not all that could happen if you didn’t have proper water damage protection in place.

Fungal growth

Moist OSB can encourage fungal growth because it already contains mold spores. Mold may thrive in even the tiniest amounts of moisture.

You must remove them as soon as possible because they might swiftly spread. Molds can cause respiratory difficulties in you and your family members, and they are also hazardous.

Fortunately, a simple water and detergent solution will do the trick. Bleach can also be used to sanitize the area and keep the pests away.


As a general rule, the drying process for OSB is gradual, but it can take a long time before all the moisture is eliminated. Slow progress might cause the sheathing to deteriorate from the inside, impacting surrounding boards ultimately.


Swelling occurs as a result of excessive moisture absorption by the boards, whether from water contact or air moisture. They don’t create leaks, but they can cause rot and fungus growth.

In any case, sanding down the thicker region and its edges will still work. Alternatively, drying the board fully may help to reduce the swelling.

How Much Moisture Does An OSB Tolerate

It’s crucial to keep in mind that OSB is water-resistant but not completely waterproof. These boards are made in a way that ensures that there are no gaps between the strands. To strengthen and seal them, they are stuffed with resin glue and wax.

Because of this, it’s best to avoid cutting boards into smaller pieces. Your boards can be irreparably damaged by excessive wetness.

OSB sheathing boards have a life expectancy that varies depending on the type of OSB used and the ambient conditions it is exposed to. You should be aware of these four grades:


As a paneling and furniture material, OSB/1 is commonly employed. When it’s wet outside, it’s ideal.


Typically utilized for weight bearing applications, OSB/2 is a thicker, stronger panel. They are best used in arid places, like the first grade.


In addition to load bearing, these can also withstand wet situations because of their water-resistant construction.


If you’re looking for a heavy-duty grade, this is the one for you!

The OSB would be more susceptible to water damage if left alone. Stain or paint can be used to increase the life of a surface. As long as they are protected by a topcoat, they will ultimately dry out if they are frequently exposed to rain.

How Long Does It Take For An OSB To Dry

OSB dries in a range of days, depending on the amount of water that has permeated the panels. Without proper treatment and protection, OSB is susceptible to deterioration from exposure to rain and humidity.

It can take up to eight weeks for the soaked panels to dry without any equipment. Swelling can become dangerously out of control if they don’t get it under control in time. As long as there is adequate air flow, you can let them to dry naturally.

Even though this can happen, there are some things you can do to avoid it:

1. Dry them as early as possible

OSBs should be dried out as soon as possible if they are exposed to water in your home. Allowing even a small amount of water to permeate the boards can have a severe impact on the panels. Using a damp cloth, remove any remaining water from the surface.

2. Use carpet drying fans and a dehumidifier

In order to speed up the drying process, carpet drying fans can be used. To put it simply, this will assist the wood’s moisture evaporate more quickly.

Open the windows and doors if it’s indoors so that more fresh air can circulate. A dehumidifier can also be used to expel dry air into the afflicted OBS. if necessary.

3. Pay better attention to the cuts and edges

Water tends to find its way into the crevices and nooks of the surface. When drying the boards, apply greater pressure to the edges to ensure that the insides are also dried.

4. Test the panels with a moisture meter

The OBS’s moisture content can be measured with moisture meters. This can be used to determine how much longer the boards will need to dry. Determine if the OBS is still salvageable or if it has to be completely replaced.

Can OSB Board Really Get Wet? (7 Things You Need To Know)

In comparison to other engineered woods, OSB is an incredibly durable product. OSB (Oriented Strand Board) is commonly used in outdoor construction because it is more durable than MDF and even plywood.

The adhesive used to bond the wood shavings together is water-resistant, so they can withstand rain and dampness rather well.

Still, water resistance isn’t quite as good as total water resistance. Also, can OSB board get wet even if it’s been exposed to a few raindrops?

Only a limited amount of OSB board can be wet. Grades 3 and 4 of OSB can soak up to a moisture content of 21% by soaking in water (without falling apart). When using wet OSB boards, you must wait until the moisture content level drops to less than 19 percent before you can begin building.

What exactly does “Moisture Content” mean? When it comes to determining wood’s moisture content, it’s all about the amount of water present.

OSB vs Plywood - Difference and Comparison | Diffen

The moisture content of green wood (wood that has just been cut from a tree) is approximately 100 percent. However, kiln-dried pressure treated wood has a moisture level of 19 percent or less.

That damp OSB board should be fine as long as the moisture content isn’t too high. Right?

It’s possible that you’d be stuck with wet OSB boards. Or, worse yet, is that OSB panel still wet on the other side? Is the quality of OSB even a consideration?

If any of these questions pique your interest, you’ve found the correct location. For the simple reason that we’ve got the solutions to the seven most important questions about the sopping wet OSB board…

No. 1) Is OSB OK To Be Left Out In The Rain?

In the event of rain, OSB is more than capable of coping. The water-resistant glue that binds all of the wood threads together was engineered to withstand rain and humidity.

Considering that most outdoor structures aren’t completed in a day. As a result, OSB roofing or siding may be exposed to the weather for weeks at a time. A little rain in the fall (or summer humidity) shouldn’t be an issue with this artificial wood.

No. 2) Are OSB Boards Waterproof At All?

OSB boards are not waterproof. They are water resistant up to a moisture content level of 21% at most.

No. 3) Is OSB Exterior Grade?

OSB boards are not water resistant. Water-resistant up to a maximum moisture content of 21%.

OSB boards are not watertight, as they are made of OSB. A maximum moisture content of 21% can make them water resistant, but that is all.

However, not all of them are appropriate for use in ‘external’ building projects.

No. 4) Is OSB More Water Resistant Than Plywood?

Plywood, on the other hand, is more susceptible to water damage. This is mostly due to the ease and rapidity with which plywood absorbs water.

Exterior Grade Plywood can’t hold a candle to OSB/3 and OSB/4 when it comes to water resistance.

In part, this is due to the fact that OSB takes a long time to absorb moisture (but can take equally as long to dry out afterwards too).

No. 5) Will My OSB Board Be OK Outside On A Humid Day?

If the OSB is of a third or fourth-grade, it can be used outside. High-humidity settings are no match for these two OSB grades.

No. 6) Will This Wet OSB Board Ever Dry Out?

Yes, OSB will dry out over time if the correct conditions are present. Those are the ideal conditions, which include a low humidity level and high air circulation.

No. 7) And How Long Does It Take For OSB To Dry?

A well-soaked OSB panel can take up to two months to dry entirely (at least without any help).

If you use dehumidifiers and fans to circulate air, drying the OSB can be completed in as little as four weeks instead of the usual eight.


Is OSB ruined if it gets wet?

Oriented Strand Board (OSB) and your framing lumber will be good. Since no one can build a house that doesn’t get wet before the roof and siding are put on, the glues used to make OSB are water-resistant. After each day’s work is completed, sweep the OSB flooring.

How do you dry OSB subfloor?

Make use of as many fans as you can to keep the room well-ventilated. Place fans aimed at the damaged sections if you have access to the flooring from a lower level. Fans should also be set to high levels and left running until the subfloor has dried fully.

How do you protect OSB from rain?

It’s best to build your shed’s exterior wall like an actual house, especially if you’re going to utilize OSB to sheathe the shed. As a result, you would need to cover the OSB with siding and then apply a moisture-resistant coating.

How can I dry plywood quickly?

To speed up the process of drying wood outside, you should arrange it in an area that receives direct sunshine. Turn on the central heating or use a dehumidifier in order to speed up the drying process of plywood indoors.

How long can OSB sheathing be exposed to weather?

OSB 3 is a moisture-resistance grade of OSB. To avoid misunderstandings, this is a risky choice. For at least four months, OSB 3 has been exposed to rain in a horizontal posture. Even puddles were being overlooked by us, despite the fact that they were developing.

Does OSB board absorb water?

Moisture is a major problem with OSB board. OSB can swell due to its thickness and water absorption capacity. OSB, on the other hand, should not be regarded as inferior just because its permeability and permeance differ from that of plywood.

Which side is OSB water-resistant?

Moisture resistance is better on the smooth side, therefore it will be better able to withstand the elements. The board’s ability to keep moisture out of the structure will be maximized if it is facing smooth side out.

What do you seal OSB board with?

Oven-curing OSB A waterproofing sealer like Thompson Water Seal, Flex Seal, or Liquid Rubber’s waterproofing sealant can be applied to the surface and edges of OSB where moisture is more likely to accumulate. Even latex paint can be applied.

Will OSB board dry out?

It doesn’t matter how many times a board is soaked by rain. Nevertheless, if they are going to be used as roofing, they should be allowed to dry completely before being installed. Having a moisture content of up to 21% is permitted if it can be shown that this falls to 18% after three months.

How do you make a subfloor dry faster?

They utilize an industrial dehumidifier to dry out the main level of the house, then drill a 4″ hole in the subfloor and blow the heated, dry air into the basement, as shown in the photograph. This reduces the relative humidity in both levels at the same time, which expedites the drying process of the subfloor.

OSB vs Plywood - Pros, Cons, Comparisons and Costs

How can I make my floor dry faster?

Use a dehumidifier with the maximum setting possible to dry the floors.. Leave it on for at least 24 hours in the middle of the room. Next, distribute fans throughout the space to ensure that the entire surface is being blown into. Set the fans to the maximum possible setting.

Does OSB expand wet?

When wet, OSB’s edges expand substantially. OSB may never regain its previous dimensions if exposed to dampness for an extended period of time. Oriented Strand Board is more susceptible to water damage than plywood, however both materials should be protected from water and moisture exposure.

Can I paint OSB for exterior use?

Sheets of OSB are available in 4-by-8-foot and 4-by-10-foot sizes. In order to protect the OSB from the elements, apply two coats of premium exterior paint. Consider the weather in your location before choosing a topcoat. Protecting OSB from the outdoors is considerably easier with the right paint.

Is OSB better than plywood?

Osb is more shear-resistant than plywood. Through its thickness, shear values are approximately two times greater than plywood. When it comes to webs of I-joists, Osb is a good choice. Performance in shear wall applications, on the other hand, depends on nail-holding ability.

What draws moisture out of wood?

Natural wood moisture absorption is facilitated by the use of baking soda. Baking soda’s hygroscopic qualities allow it to draw water molecules from the surrounding environment and so remove moisture from behind and beneath neighboring surfaces.


Because every circumstance is unique, it’s impossible to say how long it will take to dry OSB board in a water-damaged wall. It may take hours, days, or even weeks, depending on the amount of moisture in the panels. Using a drying tool will make the process go more quickly and effectively.