How to Create Slabs in BricsCAD BIM

Quick answer: DMEXTRUDE extrudes a closed 2D entity (polylines, circles, ellipses) or a detected boundary enclosed by walls and/or 2D entities. POLYSOLID creates pitched roofs.

Creating Floor Slabs Between Walls

Before starting, make sure: Enable Boundary Detection under SELECTIONMODES is on (the same setting covered on this hub’s roofs and BIM entity selection pages), the surrounding walls’ bottom faces sit in the current coordinate system’s XY-plane (move the origin if needed), and Dynamic dimensions are on.

1. Move the cursor inside the surrounding walls.
2. Once the boundary highlights, choose Extrude from the Model command group in the Quad; the slab extrudes dynamically.
3. Either type the slab’s thickness in the dynamic dimension field, or pick a point.

Creating a Pitched Roof Slab

Before starting, make sure: Dynamic UCS is on, Dynamic dimensions (DYN) are on (the Tracking dynamic dimensions option of DYNMODE is recommended), Entity Snap Tracking (STRACK) is on, and Endpoint entity snap is on.

1. Launch POLYSOLID. You’re prompted for a start point, or to choose Height, Width, Justification, Entity, Separate solids, or Dynamic.
2. Move the cursor over the outside face of a wall perpendicular to the roof slab you want to create.
3. Once the face highlights, press Shift to lock the dynamic UCS.
4. Either snap to the wall’s exterior top corner to create the roof at the top edge, or create an overhang (eave): hover over that same corner to acquire a snap tracking point (a small red cross confirms it), then move the cursor outward and type the overhang distance in the dynamic entry field.
5. Press Tab to activate the Angle field, type the pitch angle, then press Tab again to jump to the Distance field.
6. Specify the roof slab’s height, then press Enter twice, the first Enter creates the roof slab’s footprint, the second interrupts creation of a second solid; the roof slab extrudes dynamically.
7. Specify a point to define the extrusion’s length.
8. Repeat the previous steps to create more roof slabs.
9. Use CONNECTWITHNEAREST, the same shortcut mentioned on this hub’s solid connecting page, to connect the walls to the roof slabs.

Frequently Asked Questions

What’s the difference between DMEXTRUDE and POLYSOLID for slabs? DMEXTRUDE extrudes closed 2D entities or detected boundaries into floor slabs. POLYSOLID specifically creates pitched roof slabs.

How do I create a roof overhang instead of ending the slab right at the wall? Acquire a snap tracking point at the wall’s exterior top corner, then move the cursor outward and type the overhang distance.

Why do I need to press Enter twice when creating a roof slab’s height? The first Enter creates the slab’s footprint; the second interrupts creation of a second solid, letting you continue with just the one.

How do I connect the surrounding walls to newly created roof slabs? Run CONNECTWITHNEAREST after creating the slabs.