8.5′ x 20′ Deck Over Trailer Plans – 7,000 lb GVWR

Product Overview

Build your own 8.5′ × 20′ deck-over trailer with the professionally engineered Deck-Over Trailer Plans. Designed for a maximum 7,000 lb Gross Vehicle Weight Rating (GVWR), this heavy-duty tandem-axle trailer combines a full-width 8’6″ deck with a 20-foot hauling platform, making it an excellent choice for equipment, tractors, vehicles, building materials, pallets, and oversized cargo.

The finished trailer features an approximate 20′ 3½” deck length, an overall width of 102″ including the rub rails, and an approximate overall length of 301″ (just over 25 feet) including the tongue. Builders can choose multiple deck materials, permanent or removable side configurations, loading ramp styles, tie-down options, stake pockets, front rail configurations, and numerous other builder-selectable features to customize the trailer for their specific hauling needs.

Built around a rugged welded steel frame using rectangular tube main beams and tandem leaf-spring axles, this trailer is engineered for long-term durability while remaining straightforward to fabricate using common steel materials. Its full-width deck-over design maximizes usable deck space and allows wider loads than conventional between-the-fenders trailers, making it ideal for contractors, equipment owners, farms, ranches, and commercial hauling applications.

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Complete Plan Package Includes

Plan Model: MDo820DS70 (8×20-70ds-dtrailer)

• 35 Pages of Detailed Engineering Drawings
• 20 Pages of Illustrated Instructions, Material Lists, Purchased Components Lists (BOM), Engineering Considerations, and Practical Building Guidance
• Complete Material Cut List
• Purchased Components List (BOM)
• Trailer Frame Construction Details
• Axle, Suspension, and Brake Installation Information
• Multiple Deck Configuration Options
• Permanent and Removable Side Options
• Loading Ramp Design and Capacity Options
• Tie-Down, Stake Pocket, and Rub Rail Options
• CAD Files for Optional Laser, Plasma, or Waterjet-Cut Components
• Illustrated Construction Techniques and Practical Building Guidance

Trailer components, steel, running gear, coupler, lighting, brakes, wheels, tires, decking, and fabrication materials are NOT included with the plans. A matching 7K Deck-Over Trailer Parts Kit is available separately.

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Available Plan Formats

Instant PDF Download

Download your plans immediately after checkout and begin preparing your build right away. The downloadable ZIP file contains the complete engineering drawing package, illustrated instructions, material information, purchased components list (BOM), engineering considerations, CAD files for optional components, and supporting documents.

Professionally Printed Paper Plans

Prefer working from paper in the shop? Choose our professionally printed plan package.

• Engineering drawings printed on 11″ × 17″ sheets for improved readability
• Instructions printed on standard 8.5″ × 11″ pages
• Shipped flat — never rolled or folded
• Free shipping within the lower 48 states

Important: Printed engineering drawings are provided for reference during construction and should never be scaled for dimensions. Always use the dimensions and measurements provided within the plans.

CAD Files: The downloadable plans include CAD files for optional components. Customers who purchase the professionally printed paper plans can simply contact us after purchase and we’ll gladly provide the corresponding CAD files electronically.

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Heavy-Duty 20-Foot Deck-Over Design

The MDo820DS70 is our longest 7,000 lb deck-over trailer design, providing additional deck length for hauling larger equipment, longer materials, and oversized cargo while maintaining the versatility of a tandem-axle trailer. The fully engineered design emphasizes structural strength, long-term durability, and practical builder-friendly fabrication using readily available steel materials.

Its full-width deck-over layout maximizes usable deck space while optional ramps, side configurations, tie-down locations, stake pockets, rub rails, and front rail options allow builders to tailor the finished trailer for everything from equipment transport to general-purpose hauling.

Proper fabrication, welding, material selection, component installation, and load placement remain essential to the safety, durability, and long-term performance of the completed trailer.

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Customizable Trailer Options

• Permanent or Removable Side Configurations
• Multiple Deck Material Options
• Loading Ramp Length and Capacity Options
• Optional Slide-Under Ramp Storage
• Raised Front Rail Options
• Tie-Down Configurations
• Stake Pocket Options
• Heavy-Duty Rub Rails
• Tongue Tray Option
• Mounted Toolbox Option
• Spare Tire Mount Option

Thinking about customizing these trailer plans? Read When Safe to Customize the Plans before making modifications to the original engineered design.

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Matching Trailer Parts Kit

Complete your build with our matching 7K Deck-Over Trailer Parts Kit. Designed specifically for these plans, the kit simplifies your build by grouping compatible major trailer components into one convenient package.

View the Matching 7K Deck-Over Trailer Parts Kit

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Professionally Engineered Plans

These trailer plans were professionally engineered by Synthesis Engineering Services. The engineering package evaluates the trailer frame, crossmembers, suspension placement, tongue design, connection points, structural load paths, and major frame components to provide a strong, durable, and reliable deck-over trailer design.

As with any trailer project, proper material selection, fabrication quality, welding, assembly, maintenance, loading practices, and compliance with applicable laws remain the responsibility of the builder.

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Recommended Builder Experience

Intermediate. This project is best suited for builders with welding and metal fabrication experience. Familiarity with trailer construction, axle installation, suspension setup, brake installation, and 12-volt trailer wiring is recommended before beginning the project.

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Understanding Trailer Weight, GVWR, and Payload

These plans are engineered for a maximum 7,000 lb Gross Vehicle Weight Rating (GVWR). GVWR represents the maximum allowable weight of the completed trailer and everything loaded on it, including cargo, equipment, accessories, and the trailer itself.

The completed trailer weight varies depending on the materials and options selected during construction. Estimated base trailer weight is approximately 1,800+ lbs, resulting in available payload that depends on the completed trailer weight. Optional equipment such as heavier decking, permanent sides, loading ramps, toolboxes, spare tires, tie-down equipment, and other builder-selected accessories will affect the final trailer weight and available payload.

Available payload can be estimated using the following formula:

GVWR − Actual Completed Trailer Weight = Available Payload

For the most accurate payload calculation, weigh the completed trailer on a certified vehicle scale after construction. Always stay within the ratings of the completed trailer, axle, suspension, tires, wheels, coupler, hitch, and all other installed components.

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Frequently Asked Questions

What is included with these trailer plans?

Each plan package includes professionally engineered drawings, illustrated step-by-step instructions, material cut lists, purchased components lists (BOM), engineering considerations, configuration options, CAD files for optional components, and practical building guidance to help you complete your trailer project.

Are trailer parts included with the plans?

No. The plans include the engineering documentation only. Steel, axles, suspension, wheels, tires, coupler, lighting, brakes, decking, and other trailer components are sold separately. A matching 7K Deck-Over Trailer Parts Kit is available to simplify your build.

Can I customize these trailer plans?

Yes. The plans include numerous builder-selectable options, including deck materials, ramp configurations, permanent or removable sides, stake pockets, rub rails, tie-down locations, front rail options, and more. Before modifying the engineered structure, we recommend reading When Safe to Customize the Plans.

Are CAD files included?

Yes. The downloadable plans include CAD files for optional components that can be used for laser, plasma, or waterjet cutting where applicable. If you purchase the printed paper plans, simply contact us after your purchase and we’ll gladly provide the corresponding CAD files electronically.

Are the plans available as both PDF and printed copies?

Yes. Choose between an instant PDF download or professionally printed paper plans. Printed plans include 11″ × 17″ engineering drawings and 8.5″ × 11″ instruction sheets, shipped flat with free shipping within the lower 48 states.

What builder experience is recommended?

Intermediate welding, metal fabrication, trailer assembly, suspension installation, brake installation, and 12-volt wiring experience are recommended. The plans provide detailed guidance throughout the build, but basic fabrication skills are expected.

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Why Choose Johnson Trailer Parts?

Johnson Trailer Parts has been helping customers build and maintain trailers since 2000. We offer professionally engineered trailer plans, matching trailer parts kits, trailer axles, suspension systems, hydraulic components, lighting, and thousands of trailer parts backed by knowledgeable customer support before and after the sale.

Whether you’re building your first trailer or adding another workhorse to your fleet, we’re committed to providing quality products, dependable service, and the technical support you need to complete your project with confidence.

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Questions?

Need help selecting the right trailer plans or matching trailer parts kit? Our team is happy to help.

Johnson Trailer Parts
Call or Text: (602) 292-9690
Email: sales@johnsontrailerparts.com