Medium Density Overlay Plywood: What Is It?
Medium Density Overlay or MDO as it is known in the stores, is one of the several engineered wood panels that can be found on the wood market, although it might be the one with the biggest growth in popularity in the past years.
MDO is a type of material that is made from pressed plywood along with a weather-resistant resin layer that is bonded to the wood surface through an industrial process of heat and pressure.
The MDO’s main property is its overlay, which has the purpose of adding stability to the panel, resistance from unwanted substances that could damage it, and provide a smooth surface that can be painted and worked on.
The overlay usually contains around 28% of phenolic resin, which allows the MDO panels to endure water, rain, direct sunlight, chemicals, abrasion and time degradation more effectively than other materials.
MDO plywood is specifically designed to have a smooth, paintable surface, making it the number one option for those who need to paint panels for outdoor use: any paint finish is three times more durable on MDO than on any other similar surface.
The MDO’s core is plywood substrate which is the precise characteristic that sets it apart from what people usually believe are quite similar materials, like MDF, which’s core is a mix of board, wax, resin and water.
- MDO is available in different sizes. The thickness includes 3/8”, 1/2”, 5/8”, 3/4” and 1”, the width ranges from 2 to 4 feet, and the length can be 8’, 10’ or 12’
- MDO panels normally come with one side overlaid and although it is also possible to acquire it overlaid on both sides, you might have to make a special order through your timber provider
- It is weather resistant and will last years before starting to degrade
- It can withstand everyday usage and friction much better than other materials
- It can resist a lot of weight, far more than the well-known MDF. A 4”x8” sheet has a tensile strength of 90lbs
- It is cheaper than real wood panels but more expensive than MDF or other less resistant plywood panels
- Long panels of MDO will not sink in the middle (while other plywood panels do), thus offering a more stable structure when building
- The routed edges of the panels are stable enough to not splint or split
What Is It Used For?
There are two main types of MDO: special proprietary MDO plyform, which is generally used for concrete forming and construction, and regular MDO, which can be bought in most wood stores and is normally used for painting.
Because of its properties, MDO can be used by woodworkers for different purposes, the most common being:
- Indoor furniture: it offers strong structural support and will produce stable and integral pieces of furniture, countertops, etc. It is exceptionally useful when used in places that have high levels of moisture such as laundry rooms and bathrooms
- Outdoors: because of its weather-resistant properties and its smooth, paintable surface, it is normally used to make outdoor and garden furniture, from tables and chairs to children’s playgrounds
- Signs: MDO is commonly used to make painted signs that will have to be put in places where they will receive rain, sun and extreme weather conditions. Also, the overlaid surface allows the paint to adhere better than on other surfaces, offering a professional look and practical solution for outdoor signboards
- Concrete forming: although regular MDO won’t work for this type of job and a special MDO is needed, it has been gaining popularity among those who work with cement forms, especially for one time cases where the form will be used just one time
- Marine Usage: MDO is considered a great choice when working with any boat’s structure or appearance. To keep up with demand, a specially constructed Marine grade of plywood was created that can now be bought with MDO panels
Tips for Working with MDO
As stated above, MDO can resist water and extreme weather; however, it will perform better if treated when used: this can be done by applying a layer of paint or veneer that will offer extra protection to the panels and seal the edges against the damage of water absorption.
Because of the high content of fiber and resin, MDO is difficult to work when sawing or using the router. If the latter is needed, it is best to use carbide tipped bits, which will need less sharpening than normal ones.
Lastly, MDO can be nailed and drilled. Nevertheless, it is necessary to apply a coat of water-resistant material that will keep the spaces between nails and holes sealed and dry.
About the author
Chloé is writer and DIY enthusiast. She fell in love with writing at the age of 12 when she started to write for school yearbook. When she’s not writing, Chloé loves to take road trips, cook and binge watch her favourite TV shows.