How do you edit a floor slab in Revit?

Editing a floor slab in Revit is a fundamental task that allows you to adjust its shape, modify its surface elevation, or change its structural composition. You can achieve this using several key methods, primarily by editing its boundary, modifying its sub-elements to create slopes or depressions, or adjusting its type properties to define its structure and materials.

How Do You Edit a Floor Slab in Revit?

To effectively edit a floor slab in Revit, you'll typically use one of three main approaches, depending on whether you need to change its perimeter, its surface contour, or its underlying construction details.

1. Editing the Floor Boundary (Shape and Footprint)

This method is used when you need to change the two-dimensional shape or perimeter of the floor slab, create openings within it, or adjust it to align with new wall layouts.

Steps to Edit the Boundary:

Select the Floor: In a plan view or 3D view, click on the floor slab you wish to modify.
Activate Edit Boundary: On the Ribbon, within the Modify | Floors tab, click the "Edit Boundary" button.
Sketch Mode: Revit will enter sketch mode, displaying the floor's current boundary as pink lines. If there are openings, their boundaries will also be visible.
Modify the Sketch:
- Use the drawing tools (Line, Rectangle, Arc, Pick Lines) in the Draw panel to add, delete, or reshape lines of the boundary.
- Ensure all boundary lines form a single, closed loop for the main perimeter, and separate closed loops for any openings. Lines must not overlap or have gaps.
Finish Edit Mode: Once you've completed your modifications, click the green checkmark "Finish Edit Mode" in the Ribbon to apply the changes. If there are warnings, address them before finishing.

Practical Insight: This is the most common method for adjusting a floor's size, cutting out spaces for stairs, or accommodating changes in a building's plan.

2. Modifying Sub Elements (Slopes, Depressions, Drainage)

This powerful feature allows you to create complex slopes, depressions, or raised areas within the floor slab's surface. It's ideal for designing sloped floors for drainage, recessed shower areas, or varying slab thicknesses for architectural effect.

Steps to Modify Sub Elements:

Select the Floor: Click on the floor slab you want to modify in a plan or 3D view.
Activate Modify Sub Elements: In the Modify | Floors tab of the Ribbon, click the "Modify Sub Elements" button. When you select the floor, you can click Modify Sub Elements right here to access this functionality.
Adjust Elevations:
- Points: Click on any point (vertex) on the floor's surface. A temporary dimension will appear. You can drag the point up or down, or type a precise elevation value in the Options Bar or the Properties Palette.
- Edges/Lines: Select an edge or a line segment. You can drag it up or down, or enter a specific elevation.
- Faces: To raise or lower an entire face, select it and adjust its elevation.
Add Control Points/Lines:
- Right-click on the floor while in sub-element modification mode and choose "Add Point" to create a new vertex for more granular control over the slope.
- Choose "Add Split Line" to draw a line across the floor, dividing it into sections that can be manipulated independently.
Exit Mode: Press Esc twice, or click outside the floor to exit the modification mode. The floor will automatically adjust its surface to reflect the new elevations.

Practical Insight: This method is crucial for ensuring proper water runoff in wet areas like bathrooms, balconies, or parking garages, creating ramps with a varying slope, or detailing stepped floor levels.

3. Adjusting Floor Type Properties (Structure, Material, Thickness)

To change the inherent characteristics of the floor slab, such as its structural layers, materials, overall thickness, or fire rating, you'll edit its type properties.

Steps to Edit Type Properties:

Select the Floor: Choose the floor slab you want to modify.
Access Type Properties: In the Properties Palette, click "Edit Type."
Duplicate (Recommended): To avoid changing all instances of that floor type in your project, always click "Duplicate" and give the new type a unique name (e.g., "Concrete Slab - 300mm with Tile Finish").
Edit Structure: In the Type Properties dialog, next to the "Structure" parameter, click the "Edit" button.
Modify Layers:
- Add/Remove Layers: Use the "Insert" and "Delete" buttons to add or remove layers (e.g., finish, substrate, structural deck).
- Change Material: Click in the "Material" column for a layer, then click the browse button (...) to open the Material Browser and select a different material.
- Adjust Thickness: Enter a new value in the "Thickness" column for each layer.
- Set Function: Assign a function (e.g., Structure, Substrate, Finish 1, Finish 2) to each layer for proper analysis and scheduling.
Apply Changes: Click "OK" on all open dialog boxes (Edit Assembly, Type Properties) to confirm and apply your structural changes to the floor type.

Practical Insight: This is essential for creating an accurate Building Information Model (BIM) that reflects the actual construction, facilitates quantity take-offs, and supports detailed documentation.

Summary of Floor Editing Methods

Editing Method	Purpose	When to Use It	Key Action	Learn More (Autodesk)
Edit Boundary	Change footprint, shape, or create openings	Adjusting perimeter, cutting out spaces for stairs or shafts	Drawing tools to redefine perimeter, "Finish Edit Mode"	Sketching Floors
Modify Sub Elements	Create slopes, depressions, variable height	Drainage, sloped ramps, shower recesses, irregular surfaces	Dragging points/lines, entering elevation values, adding points	Shape Editing Floors
Edit Type Properties	Change structure, materials, thickness	Specifying construction details, fire ratings, material changes	Duplicating type, modifying "Structure" layers' materials/thickness	Defining Floor Types

By utilizing these comprehensive editing tools, you can accurately model virtually any floor condition required for your building design in Revit.