Updated at: 24-08-2022 - By: Sienna Lewis

When it comes to fixing waterlogged walls, how long does OSB board need to cure before it can be utilized as sheathing? You don’t want rot and mold to set in because of prolonged exposure to wetness.

Oriented strand board is one of the most flexible building materials available today (OSB). Uses range from flooring and wall sheathing to roofing and even furniture. Despite its resistance to water, this material can deteriorate much like wood. To help you out of this jam, we have compiled a list of several things you can do to your OSB boards.

What Happens When An OSB Board Get Soaked

These planks are made from engineered wood specifically to withstand the humidity and moisture levels found inside a home. However, they still shouldn’t be subjected to a deluge of water.

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OSB deteriorates faster than other wood products when subjected to extremes of moisture and humidity. Not having adequate protection against water damage could lead to other problems as well.

Fungal growth

Wet OSB, which includes mold spores already, can promote the spread of fungi. Mold may grow with very little moisture.

Quick action is needed to eradicate them before they can spread further. Molds are dangerous and can cause breathing problems for you and your loved ones.

Thankfully, all you need is a solution of water and detergent to get the job done. Bleach can be used to clean the area and deter bugs at the same time.


OSB typically dries slowly, but it may take a long time to completely remove all moisture. Sheathing may deteriorate from the inside if work is done too slowly, which could affect the adjacent boards.


Boards that have absorbed an excessive amount of moisture, either through direct touch with water or from the surrounding air, will expand. They won’t leak, but they can promote decay and mildew.

Sanding the thicker area and its edges will still do the trick, though. If it doesn’t work, maybe completely drying the board will do the trick.

How Much Moisture Does An OSB Tolerate

Keep in mind that although OSB can withstand some moisture, it is not totally waterproof. These planks are manufactured so that there are no empty spaces between the individual strands. In order to fortify and waterproof them, resin glue and wax are used as filler.

Therefore, it is not recommended to cut boards into smaller pieces. Too much moisture can ruin your boards beyond repair.

Sheathing boards made from oriented strand board (OSB) have a lifespan that varies according on the type of OSB used and the environmental conditions to which it is subjected. Remember these four levels of difficulty:


Standard oriented strand board, or OSB/1, is widely used for paneling and furniture. It’s perfect for when it’s damp outside.


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


OSB/2 is a thicker and stronger panel that is typically used for load bearing purposes. They thrive in dry environments, such as the first grade.


If you need something sturdy, this is the grade for you.

If left untreated, OSB is more likely to rot when exposed to moisture. A surface’s durability can be improved by applying a stain or coat of paint. So long as a topcoat is in place, they will dry out even if they are regularly exposed to the weather.

How Long Does It Take For An OSB To Dry

OSB dries takes a few days to a week, depending on the humidity level and how deeply the panels were wet. Wet and humid conditions can hasten the deterioration of OSB if it isn’t properly treated and protected.

Without any kind of assistance, drying the wet panels can take up to eight weeks. If they don’t get the swelling under control in time, it might become life-threatening. You can dry them naturally if there is enough air circulation.

Even while this is possible, there are measures you may take to lessen the likelihood of it happening:

1. Dry them as early as possible

If OSBs become wet inside of your house, you need to dry them out as quickly as possible. The panels can be severely damaged by even a minimal amount of water penetrating the boards. Make use of a moist cloth to wipe away any remaining water.

2. Use carpet drying fans and a dehumidifier

Carpet drying fans can be used to hasten the drying process. To put it another way, this will help the wood dry out faster.

If you’re doing it indoors, let some fresh air in by throwing open the windows and doors. One other option is to utilize a dehumidifier to force dry air into the affected OBS.

3. Pay better attention to the cuts and edges

Surface cracks and crannies are common entry points for water. When drying the boards, more pressure should be applied to the edges to dry the inside as well.

4. Test the panels with a moisture meter

Moisture meters can be used to determine the amount of moisture in OBS. If you want to know how much longer the boards will need to dry, you can utilize this information. See if the OBS can be repaired or if it has to be replaced.

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

The OSB product has a far longer lifespan than other synthetic woods. Because of its superior durability over MDF and even plywood, OSB (Oriented Strand Board) is frequently utilized in outdoor construction.

Wood shavings can endure rain and moisture because the adhesive used to bind them together is waterproof.

It’s true that water resistance falls short of the ideal of completely waterproofing a structure. What about OSB board; will it become wet if it gets a little rain on it?

Wetness on OSB board is restricted to a small area. Grades 3 and 4 OSB can absorb up to 21% moisture after being submerged in water (without falling apart). Once the moisture content of the OSB boards is below 19 percent, construction can commence even if the boards were previously wet.

How do you define “Moisture Content?” The amount of water in wood is the single most important factor in establishing its moisture content.

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Green wood, or wood directly from a tree, has a moisture level of roughly 100%. However, the moisture content of kiln-dried pressure treated wood is 19 percent or less.

As long as the OSB board’s moisture content isn’t too high, it should be fine to use. Right?

If the OSB boards get damp, you can be in a bind. How about this: is the other side of the OSB panel still wet? Is it important to care about OSB quality?

Those who find themselves asking any of the above have come to the right place. Because we know the answers to the seven most pressing concerns regarding the drenched OSB board, simply put…

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

OSB is completely watertight and will not swell or warp in the rain. All of the wooden strands are held together by a glue that can endure moisture, thus this material can be used outside.

Because most outdoor constructions don’t get built overnight. This means that OSB siding or roofing could be out in the elements for several weeks. No amount of autumnal precipitation (or summertime humidity) should harm this synthetic lumber.

No. 2) Are OSB Boards Waterproof At All?

This is because OSB boards are not watertight. The maximum amount of moisture that can penetrate them is 21%.

No. 3) Is OSB Exterior Grade?

In other words, OSB boards can easily be damaged by moisture. Up to 21% moisture content is not a problem for this material.

OSB boards, being manufactured of OSB, do not prevent water from seeping through. It is possible to make them water resistant, but only up to a moisture level of 21%.

However, not all of them can be used in “external” construction.

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

However, plywood is more likely to rot when exposed to moisture. Plywood absorbs water very quickly and easily, which is a major contributing factor.

Compared to OSB/3 and OSB/4, exterior grade plywood is not as water resistant.

OSB has a somewhat long drying time because of how slowly it absorbs water (but can take equally as long to dry out afterwards too).

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

Outdoors use is acceptable for OSB of third or fourth grade quality. Both of these grades of OSB are successful in high-humidity environments.

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

The answer is yes, OSB will dry out over time given the right conditions. Those are the best possible conditions, which include a low humidity level and plenty of fresh air flow.

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

OSB panels that have been drenched for an extended period of time can take up to two months to dry completely (at least without any help).

Drying the OSB can be done in as little as four weeks instead of the typical eight weeks with the help of dehumidifiers and fans to circulate air.


Is OSB ruined if it gets wet?

As for framing material, OSB and regular old-fashioned lumber will do just well. Waterproof glues are utilized in the production of OSB since no one can build a house without it getting wet before the roof and siding are installed. The OSB flooring should be swept at the end of each working day.

How do you dry OSB subfloor?

Use as many fans as possible to maintain adequate ventilation. If you can get to the flooring from below, you can direct fans towards the damaged areas to help them dry out. Additionally, fans should be turned up to high and left on for an extended period of time in order to ensure the subfloor dries completely.

How do you protect OSB from rain?

If you plan to sheath your shed in OSB, it’s better to construct the outer walls like those of a traditional house. Because of this, OSB needs to be clad in siding and protected from moisture with a special coating.

How can I dry plywood quickly?

Drying wood outdoors can be sped up by placing it in a spot where it will be exposed to direct sunlight. To hasten the drying of plywood indoors, turn on the central heating or run a dehumidifier.

How long can OSB sheathing be exposed to weather?

OSB 3 is a grade of OSB that has good resistance to moisture. That’s a risky move if you want to avoid confusion. OSB 3 had been lying flat in the rain for at least four months. We didn’t even see the puddles that were forming around us.

Does OSB board absorb water?

OSB board has serious issues with moisture. Due to its thickness and ability to absorb water, OSB can expand when exposed to moisture. However, just because OSB has different permeability and permeance than plywood does not indicate it is of lower quality.

Which side is OSB water-resistant?

Since the smoother side is more impervious to moisture, it will have a longer lifespan and be less likely to succumb to the weather. In order to maximize the board’s capacity to prevent moisture from entering the building, it should be installed with the smooth side out.

What do you seal OSB board with?

OSB that has been baked in an oven OSB’s surface and edges, which are prone to collecting moisture, can be sealed with a waterproofing sealer such as Thompson Water Seal, Flex Seal, or Liquid Rubber’s waterproofing sealant. Using latex paint is also an option.

Will OSB board dry out?

It doesn’t make any difference how many times rain soaks a board. However, if they’re going to be utilized as roofing, it’s important to give them plenty of time to dry out. If it can be demonstrated that the moisture level drops to 18% after 3 months, then a moisture content of up to 21% is acceptable.

How do you make a subfloor dry faster?

They dry the first floor using an industrial dehumidifier, then cut a 4-inch hole in the subfloor and pipe the dry, warm air down into the basement. This simultaneously decreases relative humidity on both floors, which speeds up drying of the subfloor.

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How can I make my floor dry faster?

To speed up the drying process, put the dehumidifier to its highest setting and place it on the floor. Put it in the middle of the room and leave it on for at least 24 hours. Next, place fans strategically around the area to achieve uniform airflow across the entire surface. Make sure the fans are turned up to their highest setting.

Does OSB expand wet?

As soon as OSB is wet, the edges grow very large. If OSB is wet over an extended period of time, it may never dry out and return to its original proportions. Both plywood and oriented strand board need to be protected against water and moisture exposure, with oriented strand board being more vulnerable.

Can I paint OSB for exterior use?

OSB is sold in sheets measuring either 4 feet by 8 feet or 4 feet by 10 feet. The OSB needs to be sealed with two coats of high-quality exterior paint to keep it safe from the weather. Choosing a coat isn’t a slam dunk, so keep the local climate in mind. With the correct paint, protecting OSB from the elements is a breeze.

Is OSB better than plywood?

Osb has better shear resistance than plywood. Shear values are roughly twice as high as plywood due to its thickness. In the case of I-joist webs, oriented strand board (Osb) is a great option. However, nail-holding capacity is crucial to performance in shear wall applications.

What draws moisture out of wood?

Baking soda aids natural wood in absorbing moisture. With its hygroscopic properties, baking soda may absorb moisture from the air and dry up spaces between and under adjacent surfaces.


It is impossible to predict how long it will take to dry OSB board in a water-damaged wall because of the variety of factors that could affect the drying process. Depending on the humidity level of the panels, the process could take anything from several hours to many weeks. When you use a drying tool, you may speed up the process and get better results.