What Is MDO Plywood? [Complete Guide]

Are you searching for a strong durable panel that can be used inside or out that has a smooth paintable or routable surface? Check out MDO (Medium Density Overlay) plywood. Never heard of it or wondering what is MDO plywood?

MDO is premium plywood with a durable weather and waterproof resin-impregnated overlay bonded to one or both sides. The smooth finish evenly accepts primer and paint, is routable, and can be used for anything from signboards to countertops and facia to wainscoting.

In this guide, we’ll explain what MDO plywood is, how it is manufactured, and its specs. We’ll identify how it can be used, advantages and drawbacks, cost, and where to purchase. We’ll also compare MDO with other plywood panels. This guide will provide you with all you need to know about MDO plywood, so you can better make decisions for material choices for your projects.

What Is MDO Plywood

What Is MDO Plywood?

MDO is a specialty waterproof all-purpose plywood panel designed for exterior use. It can be used for all applications plywood or MDF commonly are used for, both inside and out. The panels have the structural strength of plywood but the finishing quality of MDF or ‘A-grade” veneers, making them a versatile rough use and high finishing material.

The plywood layers are defect-free and of uniform density allowing for cleaner and more detailed cutting, routing, shaping, and drilling. The waterproof resin used to form the overlay or film makes the surface water and weatherproof and is thicker than a heavy block or butcher paper, and much more durable. The overlay forms a smooth surface that better accepts paint, stencils, veneers, and transfers than standard plywood.

How Is MDO Plywood Made?

MDO plywood is manufactured using thin defect-free veneer layers of B and C-grade hardwoods or softwoods. The layers are laid perpendicular to each other with a waterproof WBP (phenolic) CARB-approved glue layer between each veneer to bond and fuse them together as pressure and heat are applied.

The 1/16” overlay is made using a waterproof resin-impregnated wood cellulose fiber and fused to one or both sides of the plywood for a waterproof paintable surface. The overlay is 28% waterproof resin making it highly resistant to moisture.

MDO Specifications

MDO plywood is water and weatherproof exterior core 4×8 or 4×10 sheets in a full range of thicknesses – 1/4″ to 1-1/4” or 6mm to 30mm. Some retailers offer pre cut signage-sized panels in a variety of common dimensions such as 10”x12” and 24”x48”. The 1/16” overlay may be on one or both sides, pre-primed or not, and one side may be MDO and the other a thin waterproof paper-like backer film.

MDO panels have a tight, solid core for high strength, durability, and screw holding ability. The waterproof bond resists humidity and precipitation for a superior surface life, while the smooth surface offers better paintability and finish adhesion. The panels resist temperature extremes, UV, moisture, swelling, mold, and insects.

What Is MDO Plywood Used for?

MDO plywood is easily cut and routed into letters or shapes for signage. The smooth surface is easy to paint or apply vinyl or other medium prints or images for advertising, real estate or traffic signs, or other purposes. The solid, defect-free layers allow for a clean chip and splinter-resistant finish too.

The sheets can be used for:

  • Hard-to-maintain locations like chimney enclosures, gable ends, and fascia
  • Ideal for weatherproof garage door panels
  • Reusable emergency window and door coverage
  • Fence panels, and much more
  • The panels are even used for concrete forms and provide a smooth even finish and are easy to clean up too.

MDO is not only weather-resistant for exterior use but has interior applications too:

  • It’s also used where moisture may be an issue in bathrooms, for baseboards and floorboards.
  • Trim
  • Countertops
  • Wainscoting
  • Furniture
  • Shelves
  • Cabinetry.

They are stronger and more durable than MDF and easier to finish than standard plywood.

Advantages and Drawbacks

As with all products, there are advantages and disadvantages. Some are more apparent when compared against other materials or uses. However, looking at the product alone is the best place to start.

Durability

MDO plywood is manufactured to give it advantages over other products. It is manufactured similar to other multi-layered panels using alternating grain directional plies for strength and durability, However, MDO uses only B and C-grade wood veneers that are free of flaws or plugs.

MDO has the strength equivalent to all multi-layer plywood, plus it will withstand exposure to the elements much longer due to the use of waterproof glue. Additionally, the lack of voids, plugs, or flaws means that cuts won’t expose any weaknesses that could cause delamination, increasing its lifespan.

Weather Resistance

The use of waterproof resins to bond flawless veneer layers together makes for superior exterior grade plywood. Adding the water and weatherproof overlay to seal the outside makes MDO even more weather resistant. The absence of voids, flaws, or plugs at cut edges keeps moisture out and prevents layers from separating.

Uses

The waterproof glues and overlay make MDO an excellent choice for exterior, interior, and marine uses where moisture exposure is a risk. Use outside for gable ends, chimney chases, pillar boxes, siding, garage door panels, trailer sides, concrete forms, and storm or emergency window and door coverings.

It is used indoors where moisture may be a problem like floors, baseboards, and bathroom walls. Additionally, the smooth overlay accepts paint and finishes better than other plywood, and the absence of plugs or flaws in the layers is better for edge and face screwing, making MDO great for cabinetry, furniture, countertops, trim, wainscotting, and shelves.

How Much Does MDO Plywood Cost?

MDO is a strong, high-quality product with greater durability making it more expensive than other panels of equal dimensions. A 4×8 MDO panel may range from $40 to $180 depending on thickness, overlay on one or both sides, priming, and availability. If it isn’t available, it will need to be specially ordered, which can also add to the cost.

Is MDO Ply Waterproof?

MDO plywood is a durable, weather-resistant exterior grade marine plywood and is considered waterproof. It is manufactured using 100% waterproof glue to bond the plies of wood with the grain of each layer running perpendicular to the next, making it resistant to warping, swelling, and shrinkage.

A waterproof overlay made of 28% waterproof resin and 72% wood fiber seals the face of the panel to further enhance its resistance to water and weather. MDO has a 6% absorption rate when immersed in water for 24-hours, and will withstand immersion 24/7.

Can MDO Plywood Be Painted?

The smooth resin-saturated cellulose composition of the overlay makes MDO plywood easier to paint than wood grain and provides for a more consistent color presentation that will last three times longer than other painted plywood.

A primer, however, is necessary for paint adhesion due to the waterproof nature of the resin. MDO plywood commonly has a wood-tone overlay, although some manufacturers color their overlay for branding purposes, while others offer a pre-primed option.

What Is the Difference Between MDO and Mdf Plywood

Both products are wood panels and share some similar manufacturing processes. MDF is a medium density fiberboard made of wood fibers bonded together with resin adhesive and wax, pressed and heated before being cooled and milled to size. MDO is a quality exterior-grade plywood made of flawless B and C-grade wood veneer laminated together with 100% waterproof resin glue, heated and pressed, and covered with a medium density wood fiber or cellulose overlay, also made with waterproof glue.

Durability and Strength

MDO is more durable than MDF, it is weather and waterproof and will last indoors or out much longer than MDF in similar locations. MDO has a span strength significantly greater than MDF of equivalent thicknesses. A 3/4” – 4×8 MDF panel will bend and break under 90-pounds of pressure if not supported, whereas MDO can support three or more times that.

MDF also doesn’t handle moisture exposure well, nor does it have the structural integrity of MDO. Additionally, MDO holds screws, nails, and pegs better too.

Density

MDO plywood is denser than MDF. The materials and processes for manufacturing MDO make it denser, more durable, and stronger than MDF and will withstand dents and dings better.

Weight

MDO is not only stronger, more durable, and denser than MDF, it is also lighter. A 3/4″x4’x8’ sheet of MDF weighs between 70 and 90 pounds or more depending on the density of the core material. A similar sheet of MDO will weigh between 65 to 70 pounds depending on if there is an overlay on one or both sides.

Moisture Resistance

MDO is manufactured using waterproof glue between plies with an overlay which is 28% waterproof glue, combining to make it highly resistant to moisture, including immersion in water 24/7. It has a 24-hour water absorption rate of 6%, whereas MDF ranges from 18% to 45% depending on material thickness. Even moisture-resistant (MR) MDF has an 11% absorption rate.

Applications

MDO offers greater structural support than MDF, can be used for interior and exterior applications, and offers better screw, nail, and peg holding ability. Both provide a smooth, paintable surface and can be cut, drilled, routered, or milled. MDF tends to be more commonly used for interior applications due to its cheaper cost. MDO is used for interior applications where loading, exposure to moisture, humidity, or direct sunlight make MDF unacceptable.

Cost

The cost of MDF vs MDO depends on thicknesses and dimensions, plus if the overlay is applied to one or both sides of the plywood, and if it is pre-primed. A quick look at a local lumberyard for a 3/4″ x 4’x8’ MDF panel shows the price is $39.35 (US) and $73.88 (US) for the same size MDO with an overlay applied to one side.

MDO vs Marine Plywood

MDO is marine-grade plywood manufactured using waterproof glue and high-quality defect-free plies. Marine plywoods are as close to waterproof as possible with a wood product. MDO is commonly made with Grade-B plies on the exterior and C-grade for the core layers, while other marine plywood is exclusively made with 5 or more cross-laminated layers of Douglas fir or western larch. Both panels are manufactured without voids or air pockets.

Marine plywood, including MDO, is used to build small and large watercraft, indoor and outdoor furniture, cabinets, decks, trailers, sheds and other buildings, signs, and wherever plywood may be used and risks exposure to moisture.

Marine plywood is available in the following five grades:

  • A-A is 1/2-inch-thick 4’x8’ or 5’x12’ panels made of knot and flaw-free veneers bonded together with waterproof resin glue.
  • B-B is commonly available in 3/4″x4’x8’ sheets. It is also called face-back as there may be some surface knots on one or both faces. The interior plies, however, are clear and free of knots.
  • A-B is 3/4-thick 4’x8’ panels and has no visible knots, but has knots present on one or more plies.
  • MDO is commonly manufactured in 4’x8’ and 4’x10’ panels and is a strong, high-quality, exterior-grade product with a smooth paintable waterproof overlay. It is available in thicknesses that range from 1/4” to 1-1/4”
  • HDO is similar to MDO but has a smoother overlay finish which contains more waterproof resin. Interior layers may also have plugs but are otherwise clear of defects. HDO is available in 1/2” and 3/4″ thick 4’x8’ sheets.

What Is the Difference Between MDO and HDO Plywood?

MDO is manufactured using flawless core layers of C-grade veneers with B-grade exterior plies. Waterproof glue is used to bond and seal the layers, and a paintable wood-product overlay that is 28% resin fused to one or both sides. HDO is a high-density overlay with a higher resin content bonded to similar layers of B and C-grade veneer, but the core layers may include plugs.

Both MDO and HDO have smooth, blemish-free overlays equivalent to A-grade veneers. MDO’s overlay is better suited for paint than the harder HDO overlay, which is also smoother. HDO is available in wood-tone overlays, or black, brown, or olive colors, while MDO is opaque wood-tone, brand colored, or pre-primed white.

Where to Buy MDO Plywood?

MDO is available at most lumber or home improvement centers, although it may need to be ordered depending on your location. Smaller pieces for signs, posters, or crafts may be available at arts and crafts or hobby supply stores too. A quick internet search or some phone calls may locate a local supplier and save some legwork.

Conclusion

MDO is a high-quality, waterproof, marine-grade plywood. It is made with defect-free B and C-grade veneers cross-laminated and bonded together with a waterproof resin glue. A paintable, A-grade, medium-density resin-saturated wood fiber overlay is fused to one or both sides.

MDO is used for furniture and construction applications, both inside and out, and anywhere moisture may be a concern. Hopefully, you have a better understanding of what MDO plywood is and where it can be used, and you’re better prepared to make material choices for your project.

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