# CAD backgrounds

Source: https://meptools.com/tools/plant-room-studio/docs/cad-backgrounds/

A **CAD background** brings an existing DXF drawing in as a backdrop you can trace your plant-room
layout over — for example an architectural floor plan. Open it from the **CAD** ribbon verb →
**Import background**.

> DXF is parsed **in your browser — nothing is uploaded**. Limit: **DXF only, max 15 MB**.

## The import wizard

Importing runs a three-step wizard:

1. **File** — drop or browse for a `.dxf` file. The wizard reports what it found: detected units,
   entity and layer counts, and how many unsupported entities were skipped. You can choose whether
   to **import text** and **import dimensions**.
2. **Calibrate** — set the drawing's real-world scale. Either accept **"Drawing is already to
   scale"** (use detected units directly), or pick two points a known distance apart and enter that
   **known real-world distance**. The wizard shows the resulting scale and the drawing's span so you
   can sanity-check it (_"If these read in kilometres, your distance is off by 1000×."_).
3. **Place** — position the background. Here you can set **layer visibility & colour**, turn on
   **Snap walls/columns to CAD vertices**, and optionally **use a layer as the room outline** —
   including **Draw room from largest closed loop** to build the room directly from the drawing.

## Working with the background

Two status-bar toggles control it once loaded:

- **CAD bg** — show or hide the background underlay.
- **Snap CAD** — snap your walls and columns to the CAD geometry's vertices while drawing.

The background is a **reference layer**: it helps you trace but is not part of your equipment or
document geometry, and it isn't sent to the server on export.

## Exporting to CAD

The **CAD** verb also offers **Export to CAD**, which writes your layout to DXF with one layer per
element type. See [Exporting](/tools/plant-room-studio/docs/exporting) for formats and plan gating.