How to Use MDO Plywood for Exterior Trims

Use MDO to trim around new doors and windows.

Medium density overlay or "MDO" is a composite building material. It comes in sheets and can be used for cabinets, floor underlay or trim of any kind. Its versatility comes from dense compacted layers, and a smooth resin fiber finish. It takes any kind of paint and has become popular for exterior window and door trim. The uniformity of MDO make it a great choice when trimming a home.

Things You'll Need

• Table saw
• Paint
• Airless paint gun
• Tape measure
• Miter saw
• Finish nailer with 1 1/2-inch nails

Instructions

1. Use a table saw to cut sheets of MDO into 2-inch strips.

2. Lay the MDO out on two sawhorses. Spray the MDO with exterior paint that you plan on using when you paint the house. Spray the edges of the MDO to seal it. Do both sides of the strips.

3. Measure along the bottom of the window. Cut a strip of MDO at that measurement with the miter saw. Using a finish gun, nail the MDO to the bottom of the window, flushing it with both sides. Paint the ends of the MDO with a paint brush to seal.

4. Measure along the vertical sides of windows from the bottom edge of the MDO that you just put on, to the top of the window. Cut strips of MDO to that length. Paint the ends of the MDO where you cut it.

5. Nail the strips along both vertical sides of the window, covering the ends of the MDO on the bottom, and flushing it with the top.

6. Measure along the top of the window from the outside edges of the vertical MDO strips. Cut MDO strips 1/2-inch longer than the measurement.

7. Lay the strips on top the window, spanning over both vertical strips of MDO. Leave 1/4 inch hanging over both ends. Nail them on with the nail gun.

Tips & Warnings

• Seal around the edges of the MDO with silicone. Seal any edges that you might have missed with paint. You can also silicon the nail holes if you want, but most exterior paint will fill them.

• Always wear safety glasses when working with wood.

References

• Inside Woodworking: MDO and HDO, A Strong Choice
• Hammer Zone: Siding and Exterior Trim