Core Value of Steel Doors
It is how steel door shapes the future by invention of Sing Core.

Cold Rolled Steel Metal Door with Patina Finish Patented SingCore Substrate

Steel door technology has not made any significant improvements since the development of the EPS(Expaned Polystyrene)  core, which has higher insulation than the traditional paper and wood based core. Sing Core uses reinforced EPS or urethane foam to fill the voids of the structural torsion-box to create a strength that is approximately 30 times stronger than any other regular door made from foam. Steel doors made of patented Sing Core provides more insulation, strength, and is extremely lightweight. The result is a more eco-friendly door, stronger, and lighter, without using any heavy gauge steel

Master Inventor Peter Sing standing on long span, light weight, high strength metal panel.

This photo features Inventor Peter Sing standing on a long span light weight, high strength, fully insulated 13 ft. x 3 ft. x 1 inch steel door with 20 gauge metal under 160 lbs. of load with hardly any deflection. No steel studs, no welding. See pix of steel panels ready for door applications.

Achieve the security, safety and elegance of the most economical, advanced steel door technology to your entryway with Sing Metal Doors made in your choice of high quality stainless steel, galvanized steel or cold rolled steel.

Sing steel doors
Click the picture to see our steel door gallery!

Sing Steel Doors are the only insulated Eco-friendly steel doors that can be guaranteed true flat thanks to patented Sing Core’s torsion box/foam composite base material that not only ensures flatness at the time of manufacture but stays flat for centuries.

The only 50 year warp-free guarantee and full structure warranty



We say, “Heavy does not mean strong- and light does not mean weak.” With Sing Core products you can get extremely strong, lightweight metal doors with built-in insulation that is backed by our limited lifetime guarantee. Sing Steel doors weigh much less than other steel doors and do not require heavy steel reinforcement studs to achieve the high strength. This also means that Sing Core doors do not need expensive, heavy duty hardware that traditional steel doors require.

High Strength

Sing Core doors are stronger than steel pound for pound. Patented Sing core can reach 1,000 PSI strength vs. paper honeycomb core traditionally used in the steel industry. Sing steel doors will not dent or kink like a regular hollow core, paper core, or a foam core steel door.


Patented Sing Core costs a fraction of high-end honeycomb substrates and still outperform traditional aerospace applications in lightweight, high-strength, and eco-friendly economical solutions. This doesn’t even take into account the reduction in transportation and installation costs and the reduction in maintenance and repair costs over time.

No Welding


Sing Steel Doors are manufactured without welding which reduces labor costs, environmental and health hazards and our patented method will not compromise the integrity of the steel surface of the steel door, like welding does. No need to compromise the integrity of your steel doors by incorporating the most high precision Sing Core (+/- .006 inch) material and our patented metal fabrication process.

Custom Lite Openings

Sing Steel Doors can come complete with custom lite opening cutouts for adding glass to your door. You are not limited to the type, shape or style of cutout for your glass opening. Other steel door companies offer a variety of window openings to select from. Sing Steel Doors allow you to create any glass enhancement that you can imagine.

Steel Door Replacements

Sing Steel Doors are the number one replacement steel doors specified by architects and designers who demand high-quality and longevity backed by our rock-solid limited lifetime warranty. See our Clients List.

Steel Door Hardware

When it is of primary importance to achieve high-end security and stability of a steel door, one invariably runs into the issue of heavy steel doors causing additional strain on the structure and hardware. Patented Sing Core eliminates the heavy weight of solid steel while out-performing solid steel.

Service Industries

Sing Steel Doors are replacing other steel doors used in commercial, healthcare, educational industries as they are being retrofitted in schools, hotels, storm shelters and retail installations.

The Best light weight Steel Stile and rail doors.
Cold Rolled Steel Sliding Patio Doors

More Options to Meet Your Specifications

Sing Steel Doors are completely customizable to your specifications. For years the design teams have been working with architects, designers and contractors to solve the problems associated with pre-existing steel door technologies. There is nearly no limit to composite options that can be adapted to the sing Steel Door that will satisfy your requirements.

Variety of Applications

Patented lightweight steel door panel
Patented lightweight steel door panel

The versatility and customizable attributes of Sing Steel Doors offers almost unlimited applications including (but not limited to) bullet proof, lead lined, extreme weather, tornado, hurricane, fire door, STC rated* and acoustical applications.

Available in Any Size or Configuration

Sing Steel Doors are available to meet your specifications and are not limited to a catalog of available items. Commercial steel doors are the best steel entry doors that are available in any configuration including steel double doors and commercial exterior steel doors.

Fast Turnaround Time

Special rush orders for custom size doors can takes less than one day if we have the materials required in stock.

Eco-friendly Sing Steel

Only Sing Steel Doors are a composite of patented Sing Core embracing our true green technology for a better world and steel which is one of the most recycled materials on our green earth.

Added Security and Benefits

Sing Steel Doors have the added benefits of increased security for vandalism-proofing, protection against windstorm or other acts of god, water proofing, increased fire protection and sanitation.

Substitute Architectural Spec # 08 13 19 Stainless-Steel Doors

Hot Rolled Steel Large Sliding Doors

Beautiful Hot Rolled Steel Doors

* Note: STC rating varies according to size, thickness, skin, and other factors. Sing Core does not rate doors, although we are fortunate enough to have one of the best sound testing labs in the world, here in the Pacific Northwest. If you require a specific STC rating, Sing Core can build a door to your architectural specifications and have the resulting door tested at our rating facility for an official rating.