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3-1-1-1 True Flat Large Oversized Doors


Sing panels make large oversized doors!

Click the picture to see our oversized sliding door gallery!

Click the picture to see our oversized sliding door gallery!

The challenge for high end door makers – especially large oversized doors – is attempting to provide a high precision, true flat solution that is fully insulated, lightweight and high strength. Even the best millworks in the world are looking for solutions. Primary concerns are raised when an oversized large door is made of a beautiful exotic wood, metal door, FRP door or paint grade door. A door like this can cost tens of thousands of dollars but still has potential to warp, if not made of patented Sing Core using our premium true flat and stay flat technology.

The Only 50 Year True Flat Guarantee

Premium Sing Core doors are the only doors that can be guaranteed to be made true flat and stay true flat for 50 years in writing. These are the only insulated, lightweight, high-strength doors that do not warp, bend, twist or cup regardless of application and/or size, even if they are oversized large doors exposed to the elements. See a clients list of Sing Core doors.

Sing Core’s true flat definition far exceeds the Architectural Woodwork Institute industry standard.

Poor standard for flatness Sing standard for flatness
Door height not greater than 84 inches Any door height. Even greater than 84 inches
Allowable deflection: 1/4 inch Deflection not allowed (1/16 inch or less)*
Over 84 inches: No warranty Over 84 inches: No problem – Guaranteed

Professional Sing Core large doors outperform the national standard and 7 ft. or larger doors can be guaranteed true flat prior to placing your order. Patented premium Sing large door technology is the only insulated, lightweight, high strength  large door with the best true flat warranty in the door industry.

True Flat Guarantee premium certified true flatSing Core’s true flat guarantee is available in all products that have been designed and built for specific environmental and performance standards as specified by the architect or client. This proprietary technology ensures a specific degree of true flatness based on science that takes into consideration the height, width, thickness, skin material(s), exposure and stress.

Sing Doors are the only Eco-friendly fully insulated, lightweight high-strength doors that are true flat and will stay flat for 50 years guaranteed.

* True Flat Guarantee only applies to end product accompanied by written Sing Core guarantee. To qualify, Sing Core is involved in the design of the core and skin materials for the specific use of the product over the life of the product. Different materials may be necessary to guarantee precision and performance over time. Confer with salesperson regarding spec requirements prior to building.

Solid as a Rock

Sing Core end product compares in weight to hollow core aluminum panels, but patented Sing Core is a solid core that exceeds the performance of any other honeycomb core (or even solid cores) available elsewhere. No other affordable insulated Eco-friendly flat building material can compete in comparison to patented Sing Core’s shear strength and light weight.

Large Doors – No Problem

Copper-DoorOne of the challenges in building any wood product of any dimension where the customer desires a perfectly flat surface over long spans is impossible in many circumstances.

Patented Sing true flat technology is based on expertise in building any panel that can be guaranteed true flat and stay flat. This composite science includes the proper proportions of Sing Core, aluminum and/or other composite materials and bonding agents based on your requirements or specifications. In this way each Sing door is a work of art.

This is the proven niche specialty service provided by Sing Core to the World’s most high-end, demanding, high-profile millworks and end users for years. Due to the unique properties of the patented Sing Core material, true flat designs can come to life and deliver superior satisfaction while carrying a 50 year structural guarantee for everything from high-end homes to sliding hangar doors.

The True Flat Challenge

The true flat door is a challenge for architects, door manufacturers, millworks and general contractors, especially if the door is 1 inch thick (or more), over 8 feet wide and/or 16+ feet tall.

Aluminum composites are common in the aerospace industry, but are cost prohibitive and not insulated, sound deadening or user-friendly for mill working or broad earth-bound use. Sing Core is designed to be used in millworks and does not require any specially-trained labor or specialized equipment; treat it just like you would any other standard wood-based substrate material.

Sing Core’s true flat process utilizes vertical grain torsion-box/foam-core/aluminum composites to deliver the solution. Contact us for more information, and if you like, we will show you how to integrate this new technology into your operation.

True Flat Sliding Doors

One of the greatest attributes of your sliding door is the actual performance of the sliding door.

Certainly, upon installation, your wood sliding door or interior pocket doors may perform superbly… but for how long?

It may be important for you to seek out how to make a sliding door that has a high level of performance. And what are the benefits that will increase the performance of your sliding door? Consider:


1. True flat straight and will stay flat
2. Lightweight 1/3 the weight (or more)
3. High strength stronger than steel lb. for lb.
4. Insulated starting at R3 per inch
5. Sound-deadening starting at STC 30
6. Resistant to warp, twist & rot to meet your specifications
7. Longevity built to last for centuries
8. Guaranteed 50 year guarantee
9. Eco-friendly sustainable true green technology

Only one door company can deliver a sliding door that delivers high marks in all those important features. See our comparison chart comparing Sing Core doors panels to other door core materials.

So if you’re looking for closet ideas, sliding closet doors or double closet doors for your wardrobes that are true flat and stay flat without warping or twisting, then you might consider the Sing Core alternative.

Click here to see our galvanized steel page.

True Flat Composite Decoded

The mystery of the true flat composite materials has been solved and reduced to simple scientific process that is the key to patented Sing Core’s success in delivering a product that is true flat (far beyond AWI national standards) and will stay flat for a hundred years.

One of the key ingredients is knowing when to use patented sing core and substrate enhancers and composite materials in the proper proportions and for specific uses to deliver the high-end performance that you or your client demands.

In fact, Sing Core’s aluminum honeycomb panels are the most popular product used all over our planet from beneath the sea to outer space and everywhere in between.

Industrial – Extreme Weatherproof

oversize-large-magnetic-sliding-door-room-dividerOur industrial sliding doors and marine sliding doors are specially designed to survive the rigorous changes in the elements including exposure to extreme weather conditions.

The secret lies within the core of the sliding door which is basically one of our honeycomb panels that is the foundation for the superior performance of sliding doors that must remain perfectly straight to reduce maintenance over time.

Even though any Sing sliding door can be finished in any flat exterior building material, the aluminum sliding door is extremely popular and can easily have any other surface material, like

any wood species, concrete, glass, FRP, HPL, and can be made to be water-resistant or bullet-proof.

The Sing sliding door is not only a light door that reduces strain and wear on the door hardware, but it is also stronger than metal hanging sliding doors and even make magnificent plastic sliding doors.

And when it comes to big sliding doors, our custom oversize sliding doors continue to deliver the best results enjoyed by the top millworks and door companies in the world service the most demanding high-end users.

Meeting the Highest Demands

We maintain the highest degrees of integrity when meeting the requirements of our clients, and their customers, assuring complete satisfaction. Most importantly, proper communication is the key. If you have certain expectations – and you let us know – our team can deliver the product that matches your specifications.

simple-order-lightweight-high-strength-panel-process-length-width-thicknessSimple Order Process

At this time, we only service commercial wholesale accounts and private individuals are expected to contact their architect, designer, contractor or lumber supply to inquire about Sing Core.

Our commercial accounts find our easy online ordering system uniquely simple and pricing can be assessed by providing us with your dimensional requirements:

  1. height
  2. width
  3. thickness

along with what your preference for visual presentation (exterior skin material) and performance expectations are (noted in the comments section), we can provide you with the solution to best suit your application.

True Flat Large Oversized Door Technology

Patented Sing Core makes true flat technology possible especially when properly blended with other component materials. One example might be a 10 ft. tall 6 ft. wide warp-free pivot door blank.


10×6 ft. wide warp-free pivot door blank

Save money by purchasing Sing Core’s only Standard 4×8 Warp-free Pivot Door Blanks.

See the specific details in the photos below showing different methods for making the science of true flat technology come to life in super large doors that will not fail.

How Much Does Our True Flat Guarantee Cost?

All Sing professional products are guaranteed true flat, that means that they exceed the AWI standards for flatness, but if the specifications for your project or application requires a specific degree of flatness, Sing Core has the technology to meet the demands of the most demanding clients.

The cost is dependent on the requirements of the resulting engineered panel that meets or exceeds your expectations and can be guaranteed to meet your performance standards over time. No two true flat solutions are identical, and the price may vary according to resource and budget constraints.

Some of the materials used in our true flat composite resolutions that battle the temperature and moisture weaknesses that accompany utilizing natural components (like wood) include

Large extreme edge pivot swing doors with man door Center for Architecture Design Seattle singcoreIntegrity in Problem Solving

Our lifetime of experience dedicated to solving the challenges of architects, designers and craftsmen who serve the most prestigious clientele, especially in terms of sustainable, lightweight, super strong and true flat solutions that maintain structural integrity over many years, while retaining the beauty and elegance of natural wood (or any other desired external material) makes all the difference.

Metal is used across many industries. Metal honeycomb composite is the leader in honeycomb cores used to create stronger and lighter metal panels as well as posts and beams using much less solid metal.

Sing Core is the leading edge technology of metal honeycomb composite material that solves our future Eco-friendly energy solution by using Sing metal honeycomb composite at a fraction of the weight of solid steel, but is stronger, lightweight, and available in steel plate, steel beam and steel panels.

You cannot deny that warping doors is a challenge for high-end door makers. No other door manufacturer is willing to accept the true flat challenge.

Trust Sing Expertise

This is the reason many door manufacturers trust Sing Core with their large doors customers who desire a premium true flat door that can be guaranteed to remain true flat, regardless of application or size.

Commercial Accounts Deliver the Best Doors Increasing Consumer Satisfaction and Confidence

true-flat-doors-in-quantity-fast-delivery-coast-to-coast-compareLabor is more than half of the cost of door manufacturing. More production with less workforce means you are able to bid on large door projects and still meet the on-time delivery. Our Win the Bid program is there to help you deliver the goods to your clients that supersede any previously known door manufacturing  process.

Besides being the only Eco-friendly insulated, lightweight high-strength guaranteed true flat door, Sing Core stands behind you to increase your productivity by doubling or tripling your door production capacity without having to add more people or machines.

Click here to see a case study of 700 doors delivered in 10 days to help our clients in Chicago win the bid and guarantee on-time delivery.

New Door Manufacturing Technology

Sing Panels are changing the way doors are made: Any type, style or appearance of any door with any shape, size or number of window lite openings CNC cut-outs to offset the high labor cost of traditional stile and rail doors.

Google search lightweight high strength true flat door to see our expertise: Google Text, Google Images

Lightweight, High Strength, Affordable

Patented Sing Core is about 15% the weight of particleboard, stronger than steel pound for pound and costs less than particleboard if you factor-in shipping costs.

This technology has endless applications. Click here to see how: Door News Archive

Note: Only certified premium true flat Sing Doors qualify for 50 year guarantee.

How to BuyMetal Composite Sing Core panels are true straight, light and strong.

To order True Flat Sliding Doors submit an order form either by email,, or print and fax it to: 360.495.4585. We’ll provide a quote within one business day. If you have questions, please contact us.

Easy Ordering

All we need to know is the length, width, thickness and what you desire on the exterior, and your custom specialty panels are made to order. Getting a quote for your specialty product, is easy, thanks to our simple online order system.

Bulk Discounts

If you’re looking for a bargain price, remember, the more you order, the less expensive your total order will be per piece. Quantity and wholesale inquiries are encouraged. Feel free to contact us for more information. Click here for Closeout specials.

Fast turnaround: In you’re in a rush, only Sing Core can be custom made within 24 hours and is proudly manufactured for you in the USA.

Fast delivery: Any thickness and almost any length, less than 5 ft wide, can be made with in 48 hours if it is rush order.

SINGCORE True Flat Sliding Doors are easy to order. You may choose from our stock panels or order custom sized panels. Our price is based on the length, width, thickness, and quantity. Submit a Work Order by fax or email, and we will give you a quote within one business day. If you have a tight budget, give us a call, we might have an alternative solution tailored to your needs.


All Sing products manufactured by Sing Core are true flat. That means that they all exceed AWI standards for flatness. Some products may not maintain flatness if they are not used in the application for which they were designed and manufactured.

Example: A wood door that was designed as an interior closet door, will not perform well if installed as an exterior boat cabin door. While it may perform well upon installation, even though the door still exceeds AWI standards, it may fail and would void the Limited Lifetime Warranty if not used in the manner for which the door was designed. A door manufactured to the performance standards of an exterior marine door could be guaranteed, and would likely require additional materials, options and labor to meet the specifications and naturally would cost more than a closet door.

Suggestion: Specify your performance standards, just like our architects do, and we can manufacture any Sing product guaranteed to meet or exceed your requirements, if possible.

See also: True Flat Guarantee and Limited Lifetime Warranty