This example demonstrates how to create a complex traditional timber roof in ARCHLine.XP.

Traditional Asian roofs are excellent examples for understanding complex roof modeling because they combine multiple roof slopes, large overhangs, structural beams, columns, purlins and repeating timber elements.

Instead of creating the entire structure as a single object, the recommended workflow is to divide the building into logical BIM components and gradually increase the level of detail.

The basic workflow is:

Roof geometry → Columns → Main beams → Purlins → Rafters → Timber joints → Repeated elements → Documentation

1. Create the basic building geometry

Start with the main supporting geometry of the building.

Create the walls or reference geometry that defines the footprint of the structure.

For an open timber pavilion or tower, the column grid itself can define the basic footprint.

At this stage, concentrate only on:

• overall dimensions,
• symmetry,
• main structural axes,
• roof support positions.

Do not model detailed timber connections yet.

2. Create the main roof

Create the main roof using the Roof tool.

Traditional timber buildings commonly use roof forms based on hip, hip-and-gable or pyramidal geometry.

Define:

• roof footprint,
• eave position,
• roof slope,
• roof thickness,
• roof elevation.

For symmetrical buildings, begin with a symmetrical roof geometry whenever possible.

3. Define the roof slopes

Select the roof and adjust the slope of the individual roof planes.

The slope has a direct effect on:

• ridge height,
• roof proportions,
• eave-to-ridge relationship,
• overall architectural character.

For complex roofs, different roof planes may use different slopes.

Always check the result in both 3D View and Elevation.

4. Create the extended eaves

One of the characteristic features of traditional Asian timber architecture is the large roof overhang.

Adjust the roof contour so that the eaves extend beyond the supporting walls or columns.

The overhang should be defined according to the architectural proportions of the building.

At this stage, concentrate on the main roof shape. Detailed curved or decorative eave components can be added later.

5. Add the main columns

Create the vertical timber structure using the Column tool.

Place columns at the primary structural positions.

Define the required:

• width,
• depth,
• height,
• material,
• elevation.

For traditional timber structures, the columns usually form a regular structural grid.

Create one correctly configured column first, then copy it to the other positions.

6. Add the primary beams

Use the Beam tool to create the main horizontal timber members connecting the columns.

These beams form the primary supporting frame below the roof.

Define the beam:

• cross-section,
• material,
• elevation,
• start and end positions.

Whenever several identical beams are required, create one correctly configured element and then copy or mirror it.

7. Create the ridge beam

Create the main structural member along the roof ridge.

The ridge beam should follow the geometry of the roof and provide a reference for positioning the secondary roof structure.

Check its position in:

• Floor Plan,
• Elevation,
• Section,
• 3D View.

For more complex roof forms, several ridge or hip supporting members may be required.

8. Add purlins

Create horizontal purlins between the eaves and the ridge.

Purlins provide intermediate support for rafters and other roof components.

Depending on the size and slope of the roof, several purlin levels may be required.

Create the first purlin at the correct elevation and offset, then copy it to the other required positions.

For symmetrical roofs, use mirroring whenever possible.

9. Create inclined rafters

Create the rafters as inclined structural members following the roof slope.

The start and end elevations of each rafter must correspond to the supporting beams and purlins.

A practical workflow is to position the rafter first in Floor Plan and then adjust its vertical position in Elevation or Section.

Check that the upper surface of the structural system follows the roof geometry correctly.

10. Repeat the rafters

Once one rafter is correctly positioned, use it as the basis for the remaining structure.

Copy the rafter at the required spacing.

For symmetrical roof planes, the same geometry can often be mirrored to the opposite side.

This approach provides two important advantages:

• faster modeling,
• consistent geometry.

Avoid modeling identical rafters individually.

11. Model hip and corner rafters

Hip roofs require additional structural members along the diagonal intersection of roof planes.

Create these members according to the hip geometry.

Because their length and orientation differ from ordinary rafters, check their position carefully in 3D.

The roof surface itself provides a useful geometric reference.

12. Create special timber profiles

Traditional timber buildings frequently contain structural members with more complex cross-sections than simple rectangular beams.

Create a custom profile when a standard beam section is insufficient.

Custom profiles can be used for:

• shaped beams,
• decorative structural members,
• brackets,
• historic timber profiles,
• special supporting components.

Create the profile in 2D and use it as the cross-section of the corresponding structural component.

13. Model tenon-and-mortise connections

Traditional timber architecture frequently uses tenon-and-mortise joints instead of simple overlapping structural members.

These joints can be represented at different levels of detail.

For an architectural BIM model, a simplified representation is often sufficient.

For restoration, heritage documentation or detailed visualization, the connection can be modeled more accurately.

Typical examples include:

• beam-to-column connections,
• intersecting beam connections,
• beam extensions,
• notched beams,
• overlapping members,
• tenon-and-mortise joints.

Use custom profiles and 3D modeling operations where detailed geometry is required.

14. Create repeating timber assemblies

Traditional roofs may contain hundreds of similar structural components.

Identify repeating parts of the structure before creating them individually.

A repeating assembly may contain:

• a short beam,
• bracket,
• supporting member,
• decorative timber element,
• connection component.

Create and verify one complete assembly first.

Then duplicate it around the building using copy, mirror or other repetition methods.

15. Add secondary and decorative elements

Once the primary structural system is correct, add the smaller components.

These may include:

• secondary beams,
• brackets,
• decorative rafters,
• fascia elements,
• exposed timber details,
• ornamental roof components.

These elements should be added only after the main structural geometry has been verified.

This keeps the model manageable during the earlier design stages.

16. Check the roof structure in Section

Create one or more sections through the building.

Sections are especially important for complex timber roofs because they clearly show the vertical relationship between:

• columns,
• beams,
• purlins,
• rafters,
• roof planes.

Check that the supporting elements meet correctly and that no structural members extend unintentionally through the roof surface.

17. Check the model in 3D

Inspect the complete roof from several directions.

Use 3D views to identify:

• incorrect beam positions,
• missing rafters,
• incorrect elevations,
• unwanted intersections,
• misaligned structural members,
• inconsistencies between symmetrical parts.

For complex structures, temporary hiding of the roof covering can make the timber structure easier to inspect.

18. Complete the architectural roof

After the structural system has been checked, display the roof covering again.

The architectural roof and timber structure should now form a coordinated model.

At this stage, add the remaining architectural details required for the project.

The result is not simply a visual 3D model: the roof remains composed of identifiable and editable BIM components.

19. Generate drawings from the model

The completed BIM model can be used to generate project documentation.

Typical drawings include:

• Floor Plan,
• Roof Plan,
• Elevations,
• Sections,
• construction details,
• structural diagrams,
• 3D views.

Because these views originate from the same BIM model, changes to the roof geometry or structural components can be reflected consistently throughout the project documentation.

20. Extract quantities

Individual columns, beams and other structural components can contain BIM information.

This allows the model to be used for quantity calculations.

Depending on the level of detail, information can be extracted about:

• number of columns,
• number of beams,
• number of rafters,
• element dimensions,
• element lengths,
• cross-sections,
• materials,
• timber quantities.

The detailed roof model can therefore support both architectural documentation and quantity takeoff.

Recommended modeling strategy

When working with a complex timber roof, avoid starting with the smallest details.

Build the model hierarchically:

1. Main roof geometry

2. Columns

3. Primary beams

4. Ridge and hip structure

5. Purlins

6. Rafters

7. Timber connections

8. Repeating assemblies

9. Decorative details

This large-to-small modeling strategy makes even highly complex traditional roof structures easier to understand, modify and maintain.