Floor Slabs and Roofs are horizontal BIM objects you draw in BIM Mode. Use a Floor Slab for structural floors between stories, and a Roof for the top of the building. Both start flat; you can shape a roof into a gable or hipped form by splitting its top face and lifting edges.

Before you start

BIM Mode is available on the Pro, Organization and Enterprise plans. It isn't included in the Free or Starter plans.
Draw roofs on the story above your top occupied floor. For a one-story villa, draw the roof on the second story.
If you model with spaces first, Sketch to BIM (in the BIM Mode toolbar) converts them to BIM objects and places a roof on the top story for you. Use the steps below to add or replace slabs and roofs by hand.

Note: Floor Slab is the structural slab (older projects and articles call it "Slab"), and Flooring is a separate object (formerly "Floor"). Roof is its own category, separate from Floor Slab.

Draw a floor slab or roof

Switch to BIM Mode.
Pick a draw tool from the top toolbar: Line (L), Arc (A), Circle or Rectangle (R). The object types appear in the Object Type Panel.
Choose Floor Slab or Roof.
Choose a type from the dropdown and set the thickness with the slider or by typing a value.
Choose a draw mode: freeform, or one of the offset modes (Center, External, Internal).
Click on the canvas to draw the outline. Type a dimension at any point for accuracy.
Close the outline, or press Enter to finish. Snaptrude creates a single solid object from the profile.

Freeform mode

Sketch the boundary of the slab or roof directly. The object is generated from the closed profile you draw.

Offset modes

Offset modes create a band of a fixed width along the line you draw. Pick Center, External or Internal to set which side of your line the width goes, then enter the offset width before drawing. This is useful for a slab edge around an existing slab, or for quick rectangular strips of a known width.

Roof types and properties

Select a roof and open the Properties tab in the right panel to edit it. Roof properties are:

Roof Type: the default types are Generic Roof, RCC Roof, Metal Deck Roof and Asphalt Shingles. On the Organization and Enterprise plans, the Team Library has a Roof section for your team's own roof types.
Roof Thickness
Roof Overhang: extends the roof beyond its drawn outline. Tape measure dimensions update after you change the overhang.

Floor slabs offer types such as Generic Slab and Metal Deck Slab. For both objects, the Properties panel also shows read-only information such as length, area, volume and story.

Note: Roof area is excluded from net and gross area by default, and roofs are listed as their own category in the Take-Off tab (BIM Mode) and in Export > Take-off. Roofs export to the Revit Roof category.

Add custom properties

Floor slabs, flooring, ceilings and roofs support custom properties, so you can record project-specific data (for example, fire rating or a specification code) on each object. Select the object and look for its custom properties in the Properties panel. Custom parameters export to Revit as shared parameters through Snaptrude Manager.

Changes to these objects are also tracked in the project's change log. Open it from the project-name menu under Export > Change Logs.

Change thickness and shape

Select the slab or roof.
Change thickness in the Properties panel, or press P for the Edit tool and drag a face, edge or vertex.
Use the arrow keys while dragging to lock movement to an axis.

Thickness follows the object's construction layers: editing it changes the structure layer. Editing tools such as Move (M), Copy/Array (C), Rotate (Q) and Flip also work on slabs and roofs, and the Offset tool (F) works on floor slabs.

Model a gable roof

There is no slope-arrow tool. You create slopes by splitting the roof's top face and raising the split edge.

In plan or 3D, draw the roof footprint with Roof selected in the Object Type Panel.
Select Split Face. Hover along one short side of the roof to find its midpoint and click.
Hover along the opposite side to its midpoint and click to place the ridge line.
In 3D, press P for the Edit tool, then hover near the ridge line and press J to switch to edge and vertex editing.
Click the ridge edge and move it up. Type the ridge height to set it exactly.
Use the Edit tool on the gable-end walls so they meet the underside of the roof.

Model a hipped roof

Draw the roof profile in plan with Roof selected.
Use Split Face to divide the top face into the sections that will slope (ridge and hip lines). Split Face accepts polylines on any face.
If the roof is symmetrical, you can delete repeated sections and copy them back later. For an asymmetrical roof, keep all sections and edit each one.
Press P, then J near an edge or vertex, and raise the ridge and hip edges to the required height. Type the vertical height for accuracy.
Copy, then flip or rotate sections to complete the roof.

Tips

Use the same Edit tool and J edge editing on a floor slab to make a simple ramp.
Editing edges or vertices sets the structure layer thickness to "Variable".
If you split a face in the wrong place, erase the split line with Erase Edge (E). You cannot split across an existing split line.
Floor slabs and roofs aren't supported in Smart Layouts, and floor slabs don't follow parametric wall edits.

Note: Cutting holes in a floor slab is supported through the Snaptrude plugin API (see docs.snaptrude.com). Contact Snaptrude support if you need to cut openings in a slab.

Walls
Sketch to BIM
Construction Layers
Edit Tool and Edge Editing
Split Face
Keyboard Shortcuts

Floor Slabs and Roofs (Flat and Sloped)