Room Dimensions Requirements for Installing a Linear Accelerator

Last Updated: October 23, 2026

What are the vault room dimension requirements to install a linear accelerator?

This is a question we often field at ROS. It is also not always easy to find and compare room planning requirements for various linear accelerator models in one place.

We recommend referring to the manufacturers’ current installation manuals, Product Planning Guides (PPG), Designers’ Desk References (DDR), site planning guides, and project-specific documentation for the exact model of the linac being installed. Precise dimensions for minimum room sizes and other parameters may vary by system configuration, site conditions, shielding requirements, local regulations, and utility requirements.

Nonetheless, general room dimensions can be helpful when planning a new vault, evaluating a replacement project, or determining whether an existing treatment room may be suitable for a different linear accelerator. The figures below are intended as general early planning references only. They should not be used as construction drawings or treated as guaranteed minimum functional room sizes.

General Room Dimensions for Linear Accelerators 

Linear Accelerator	Approx. Room Height	Approx. Room Width	Approx. Room Length	Base Frame / Floor Pit Dimensions (L x W x H)
VARIAN
TrueBeam (Slim Stand)	9′	19′ 4″	19′ 4″	12′ 4″ x 5′ 6″ x 1′
TrueBeam (Long Stand)	9′	20′	20′ 6″	12′ 4″ x 5′ 6″ x 1′
Halcyon / Ethos	9′	15′ 1″	19′ 5″	5′ 10″ x 2′ 5″ x 1′
High-Energy / Dual-Energy C-Series (Clinac iX / Trilogy)	9′	20′	25′	12′ 4″ x 5′ 6″ x 1′
Low-Energy / Single-Energy C-Series	9′ 6″	20′	22′	12′ 4″ x 5′ 6″ x 1′
ELEKTA
Synergy	10′ 6″	19′ 8″	20′ 9″	5′ x 4′ 7″ x 9″
Versa HD	10′ 6″	21′ 9″	20′ 2″	5′ x 4′ 7″ x 9″

Note: The general table is intended for early planning only. Values are based on available manufacturer planning documents, diagrams, and reference materials. Meeting these approximate dimensions does not guarantee that a room is fully functional or suitable for installation. Final room requirements should always be verified against the current OEM DDR, PPG, site planning documentation, and project-specific site conditions. For the C-Series entries, pit dimensions assume a Universal VEO base frame; installations with earlier base-frame configurations may differ.

Common models discussed in more detail below include Varian TrueBeam, Varian Halcyon / Ethos, and Elekta Versa HD.

General Linear Accelerator Room Planning Considerations

• Treatment vault dimensions, ceiling height, and clearance around the machine, couch, and gantry
• Floor pit, base frame, and structural requirements
• Shielding, maze or direct-door entry, and physicist review
• Electrical service, grounding, warning lights, door interlocks, and safety systems
• Cooling, HVAC, chilled water, ventilation, and utility routing
• Control area layout, IT/network requirements, service access, and maintenance clearance
• Rigging path, doorway width, hallway turns, elevator access, floor loading, and rigging capacity
• Future equipment needs and overall clinical workflow

Varian TrueBeam Room Dimensions

There are two types of Varian TrueBeam installations that may require different vault room dimensions. They are often referred to as Long Stand and Slim Stand, sometimes referred to as SVC for small vault configuration. As a general rule, TrueBeam systems with serial numbers below 2000 are often treated as Long Stand systems, while serial numbers 2000 or higher are typically Slim Stand systems. Final requirements should still be verified against the relevant Varian PPG or DDR.

• Minimum Pit Dimensions – 5′ 6″ wide x 12′ 4″ long minimum (1′ deep)
• Minimum Ceiling Height – 9′ finished floor to finished ceiling; additional height is helpful for rigging and ceiling-mounted components
• Slim Stand Approx. Minimum Room Clearance – approximately 19′ 4″ x 19′ 4″ wall to wall
• Long Stand Approx. Minimum Room Clearance – approximately 20′ 6″ x 20′ wall to wall

Varian Halcyon / Ethos Room Dimensions

The Varian Halcyon and Ethos systems use a compact, enclosed Varian platform with similar room planning dimensions. Ethos adds adaptive radiotherapy capabilities, so Ethos planning should also account for IT/network requirements and the Adaptive Server Appliance.

• Approx. Minimum Room Clearance – approximately 19′ 5″ long x 15′ 1″ wide, based on the ideal minimum room clearance diagram
• Minimum Ceiling Height – 9′ above finished floor
• Minimum Treatment Floor Pit Dimensions – approximately 5′ 10″ long x 2′ 5″ wide x 1′ deep
• Additional Planning Notes – local electrical and regulatory workspace clearances are not included in the ideal minimum room clearance diagram. Ethos planning should also account for IT/network requirements and the Adaptive Server Appliance.

Elekta Versa HD Room Dimensions

The Elekta Versa HD remains a common system for new and replacement vault planning. As with the Varian systems above, the figures below are general planning references and should be verified against the current Elekta site planning documentation and project-specific site drawings.

• Minimum Ceiling Height – 10′ 6″ finished floor to finished ceiling, with higher clearance recommended for rigging and ceiling-mounted components
• Approx. Minimum Room Clearance – approximately 21′ 9″ x 20′ 2″ wall to wall
• Treatment Table Pit Dimensions – approximately 5′ x 4′ 7″ x 9″ deep

Conclusion

There is not a one-size-fits-all blueprint for installing a linear accelerator. General room dimensions can be useful during early planning, but meeting an approximate footprint does not guarantee that a room is ready or functional for installation. The full site review should also account for shielding, pit compatibility and structural requirements, utility routing, service access, rigging capacity, future equipment needs, clinical workflow, and local code or regulatory requirements before finalizing a room design.

Whether you are planning for a TrueBeam, Halcyon, Ethos, Versa HD, or another linear accelerator model, the best approach is to use the current manufacturer planning documents and coordinate closely with your physicist, architect, contractor, and equipment project team.

For further information, contact ROS to learn how we can help with linear accelerator installation planning, floor pit or base frame planning, mechanical and electrical preparation, and room readiness.

Linear Accelerator Room Dimensions Frequently Asked Questions

Note: These answers are for early planning only. Always verify final room requirements using the current manufacturer PPG, DDR, or site planning documentation for the specific system being installed.

What is the typical room size for a linear accelerator?

Typical linear accelerator room dimensions vary by model, system configuration, and site conditions. Many traditional linac vaults are around 20′ wide by 20′ to 25′ long, while some compact systems may fit into smaller rooms. Ceiling height, floor pit or base frame requirements, shielding, utilities, and clinical workflow also need to be reviewed before finalizing a room design.

Can a linear accelerator fit in an existing vault?

Yes, many replacement linacs can fit in an existing vault. However, the room still needs to be reviewed for ceiling height, shielding, floor pit or base frame requirements, utility routing, cooling, electrical service, service access, and rigging access. Meeting a general footprint does not automatically mean the room is ready for installation. A qualified medical physicist should also reassess existing vault shielding when replacing a linac, particularly if the new system uses higher beam energies.

What room dimensions are needed for a Varian TrueBeam?

A Varian TrueBeam may require different room dimensions depending on whether it is a Slim Stand or Long Stand configuration. As a general planning reference, a TrueBeam Slim Stand may fit in a room of approximately 19′ 4″ x 19′ 4″, while a TrueBeam Long Stand may require approximately 20′ x 20′ 6″. Both should be verified against the current Varian PPG or DDR for the specific system and project.

What room dimensions are needed for Varian Halcyon and Ethos?

Varian Halcyon and Ethos use a compact, enclosed Varian platform with similar room planning dimensions. As a general planning reference, both systems are commonly listed with an approximate room clearance of 19′ 5″ long x 15′ 1″ wide, with a 9′ ceiling height and a treatment floor pit of approximately 5′ 10″ x 2′ 5″ x 1′. Ethos planning should also account for IT/network requirements and the Adaptive Server Appliance.

What room dimensions are needed for Elekta Versa HD?

Elekta Versa HD is commonly listed with approximate room clearance of 21′ 9″ x 20′ 2″, with a 10′ 6″ ceiling height and treatment table pit dimensions of approximately 5′ x 4′ 7″ x 9″. Final dimensions should be verified using current Elekta site planning documentation and project-specific site drawings.

What else matters besides linear accelerator room dimensions?

Room dimensions are only one part of linac installation planning. Facilities also need to plan for shielding, floor pit or base frame requirements, utility routing, electrical service, cooling, HVAC, control area layout, service access, safety systems, rigging access, future equipment needs, and clinical workflow.