Doors and Moisture: How to Prevent Warping, Bowing, and Costly Mistakes

featuring Triline Cavity Sliding Door solution

28 April 2026

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Here, we explore why doors bow, how temperature and moisture affect their straightness, and the crucial steps to take when handling, storing, and sealing doors to prevent these issues.

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Why Do Doors Bow?

Doors bow when the wood within them absorbs or releases moisture unevenly, causing one side of the door to shrink or swell more than the other. This imbalance results in a curved, or “bowed,” appearance. Environmental factors such as changes in humidity, moisture exposure, and fluctuating temperatures can accelerate this process, affecting the stability of the door.

Wood, being a hygroscopic material, readily absorbs or expels moisture depending on its surroundings. When doors are exposed to high humidity, they may expand; when exposed to dry conditions, they may shrink. If this process happens unevenly, such as when one side of the door faces a different temperature or moisture level than the other (common in improperly sealed doors), bowing occurs. Bowing is not just an aesthetic issue but can lead to functional problems, particularly in interior sliding doors or pocket doors, which rely on precise clearances.

How Moisture and Temperature Affect Door Straightness

Doors that are exposed to fluctuating moisture levels or temperature changes are highly susceptible to warping. In high-humidity environments, wood absorbs moisture and swells, which can cause bowing. Conversely, in dry conditions, the wood loses moisture, leading to shrinkage. If the door is not properly sealed, moisture will penetrate the wood unevenly, increasing the likelihood of warping.

Temperature changes further complicate the issue, as wood expands when warm and contracts when cool. For pocket door systems or taller doors, this can cause serious issues due to the tight tolerances within the frame. If a door bows inside its pocket, it may scrape against the sides, damaging both the door and the surrounding structure. For taller internal sliding doors, even a small amount of warping can make them difficult to open or close properly.

How to Store Doors Correctly

Proper storage of doors before installation is critical to maintaining their structural integrity. Doors should be stored flat on equal-sized packing boards in a dry, well-ventilated area, away from direct sunlight, moisture, and other environmental factors that could cause them to warp. Doors must not be stacked directly on the ground, as this can expose them to dampness and humidity, which can cause bowing. Avoid storing them in freshly plastered or damp areas, as this can increase their moisture content abnormally.

To allow for acclimatization, doors should be conditioned to the building environment before installation. This minimizes the risk of warping as they adjust to the site’s specific temperature and humidity levels.

How to Treat Doors Upon Receiving Them

The moment doors arrive on-site, they need to be treated with care to prevent warping or bowing. As outlined in AS 2688:2017, it is crucial that doors are sealed on all four edges and both faces within seven days of arrival. The sealer used should effectively prevent moisture from being absorbed into or expelled from the door. Failure to carry out this sealing will void any warranty on the product. It’s important to note that using water-based sealers or diluted paints will not properly seal the door and may lead to long-term damage.

Sealing the entire door, including all edges and grooves, is not just a recommendation but an essential requirement under AS 2688:2017. Ensuring that doors are properly sealed before installation can significantly reduce the risk of warping, bowing, or cracking, helping to maintain both the functionality and appearance of the door.