There are 2 of the most popular types of paintgrade options available for your architectural door specs from Sing Core, and each includes patented Sing technologies to maximize the potential of these formats, ensuring you can enjoy the only

50-year Warp-free Guarantee

Sing Core Paintgrade Door Blanks


The secret to creating an incredibly smooth paint grade door is what lays underneath the painted surface. At Sing Core, the True Flat Team is likely to suggest using a 1/8″ MDF over 1/4″ Plywood surface for the smoothest surface area. Another alternative would be  3/8″ Marine Plywood, which would require a preparatory priming prior to painting for a perfect paint job. Of course, your door will only remain straight for 50 years, if you have Sing Core technology inside.

  • Warp-free MDF is lighter in weight and stronger than other MDF.
  • Average 1.5-inch to 3-inch thick MDF paintable door blank weighs approximately 1.5 to 3 lbs.
  • The surface of MDF is very smooth which makes it great surface for painting.
  • MDF is very consistent throughout, so cut edges appear smooth and won’t have voids or splinters.
  • Because of the smooth edges, you can use a router to create decorative edges.
  • Warp-free MDF is excellent substrate for applying .020-inch wood veneer or other thin laminates. (see below)
  • Made from multiple layers of wood veneer, marine plywood is a strong wood fiber material.
  • Marine plywood is water resistant and good for use in exterior door applications.
  • Marine plywood face grain can be easily stained.
  • Marine plywood holds screws very tightly since the varying grains of wood on each layer give the screws something to hold onto.
  • Marine plywood is an excellent substrate for applying natural wood stave, wood planks, or other materials. (see below)
.020 Walnut Veneer over extremely smooth Warp-free MDF

The most popular and least expensive is marine plywood.

Warp-free patented and patent pending Sing Core marine ply door substrate

Our marine ply is used in oversized exterior door applications and is constructed using water resistant adhesive using an A-grade veneer face, C-grade inner plies, and a B-grade back which is used for securing patented Sing Core. Marine plywood is a better grade of plywood, commonly used in cabinetry, where the backside need not be presentation quality.

16 ft Tall Billionaire’s Teak plank front Door on Warp-free marine plywood

The 16 ft tall door (above) is teak wood stave door for a mansion in Beverly Hills with Sing Core inside and can be guaranteed not to warp, bend, twist, or otherwise fail for 50 years.

The A-grade is the highest quality veneer and most sheets will be free of flaws resulting in a plywood surface that is smooth and can be prepped and painted easily.

Warp-free MDF Guaranteed True Flat for 50 Years

The above picture shows MDF substrate ready for paint grade or laminating thin veneer. We work with millwork companies and high end door manufacturers to provide the most strong, lightweight, non-warping door with best guarantee in the USA.

Large barn sliding door with paint-grade 1/4″ marine ply skin.

Warp-free MDF

Sing Core’s MDF is not your father’s MDF. Inventor Peter Sing has developed a method or creating a perfectly smooth surface, which is a well-known characteristic of MDF, which is lightweight MDF and will not warp. Moving due to lack of strength, especially amidst long spans, is also a well-known characteristic of MDF.

Sing uses a combination of patented and patent-pending technologies which result in the only large warp-free MDF door blanks in the door industry. That’s why Sing Core is known for creating the highest grade MDF in the door industry.

When making big doors, like the large oversized doors which Sing Core is famous for, to try to use MDF without Sing Core inside would be like building a door with a giant noodle, granted the surface would still be smooth as can be.

Because MDF is not water resistant it is not recommended for exterior applications, so avoid specifying MDF for large entry doors due to its inherit weakness, instead spec marine plywood as your base material instead.

Due to the smoothest surface area material, MDF can easily be painted, or used as underlayment for thin veneers, vinyl, or other laminations.

16 ft tall White Oak veneer pivot doors on warp-free MDF top floor World Trade Center

The above doors are 16 ft. tall feature .o20 white oak veneer. Door substrate made of patented Sing core with MDF substrate for the tallest building in North America, on the 86th floor’s Sky Club atop the New York World Trade Center.

In fact, all the most high-end veneer-work done by Sing Core uses this warp-free MDF solution as underlayment for the perfect veneering for which they are known. See: How to Make the Best High-end Veneer Doors. Likewise, their high-end millworks and door companies who apply their own laminates, they order this material as their gold standard.

On the other hand, if your intention is to add natural wood planks, then marine plywood is preferred substrate, especially for exterior doors.

While marine plywood and MDF are the most popular there are many other skin types for plywood, paintgrade, and others.

Now, maybe you have a better idea about why architects spec Sing Core