How to Flatten Warped or Bent Plywood

So your plywood is bent, cupped or bowed? You will need to apply some hot water with a sponge or rag to the concave side of the board (image below).

I fixed a small piece of 1/2″ or 12 mm plywood board with a bad bow.

If the warp is only present in one section of the board then you only need to dampen on the concave side of that specific area.

 

If you need a sponge.

Put the board in direct sunlight with the wet side facing downwards. The resting surface needs to be flat I decided to use our driveway.

Place some form of weights on the upper side I used pavers. Leave the board to dry and the bowl should disappear within an hour depending on how hot it is. The temperature was about 88 Fahrenheit or 31 Celsius.

Check the board every 20 minutes to see how things are going. If you overcook the board it will warp in the opposite direction.

After an hour had passed the original bow was gone but I overcooked the board which now has a slight warped facing upward and is 90 degrees offset from the original bow.

To fix this I’ll wet the concave side of the new warp and place it face down and leave it to cook for just 30 minutes.

This the three sides of the plywood board are perfect and the other edge has a tiny warp on one side which is okay for my needs.

I know this fix is limited to sunny conditions so some of you may have to store your warped plywood until the Summer arrives.

I would recommend securing the board with screws as soon as possible after fixing the warp as some boards just want to return to being bent for life.

 

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