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Escape route checker

About this app

Floor plan as a heat map of walking distance: drag stairwells and check the 35 m rule and the second escape route.

With explain mode: an AI tutor walks you through the app, points out what matters in the scene and answers your questions.

What the 35 m rule requires

Under § 28a(2) of the Baden-Württemberg building code (LBO), at least one exit into a required stairwell or to the outside must be reachable within 35 m from every spot in a habitable room. § 15(3) requires two independent escape routes for every occupancy unit on each storey with habitable rooms; both may run through the same required corridor within the storey. Several required stairwells should lie as opposite as possible. The second route can be another stair or a spot reached by fire service rescue equipment; a smoke-proof stairwell makes it unnecessary.

What the app shows

You see the floor plan of one storey at an angle from above, to scale with rulers. The floor is a heat map: every spot is coloured by the shortest walking line to the nearest exit, with contour lines every 5 m. Above the limit the map is hatched red. The LBO says “distance” and names no method; the app measures along the walking line through the door centres and says so. The check panel lists the rules with traffic lights and sections, including corridor width 1.25 m, stair 1 m and smoke sections up to 30 m. The app is an illustration, not a smoke or evacuation simulation and not legal advice.

What you can try

Drag a stairwell along the exterior wall towards the middle and the red corners grow. Tap a spot: a line of light runs around the walls to the exit, the dashed straight line is visibly shorter, and a second line shows the second escape route. With “Fire in stairwell A” the map recalculates. You can move corridor walls, tap doors and smoke barriers, and switch between office floor, school under the 2025 model school building guideline and assembly venue under the VStättVO BW. The examples office block, school wing, dead end, L-shape and hall show typical solutions and one violation.

Frequently asked questions

Is the 35 m rule measured as the crow flies or along the walking line?
§ 28a(2) of the Baden-Württemberg LBO says “distance” and names no method. The assembly venue regulation says explicitly in § 7(1) that distance is measured along the walking line. Designers therefore plan with the route around the walls and through the doors, since that is the only way a person can walk. The method should be agreed with the building authority in each case.
Are two stairs side by side two escape routes?
Escape routes must be independent of each other, and under § 28a(2) LBO several required stairwells should lie as opposite as possible. Two stairwells in one place meet this poorly, because both routes run in the same direction almost everywhere. It is allowed for both routes to run through the same required corridor within a storey.
May the second escape route use the fire service ladder?
Yes, under § 15(5) LBO the second route can be a spot reachable by fire service rescue equipment if access and suitable set-up areas are provided. If the ladder access point is more than 8 m above ground, § 15(6) requires a driveway; a passage is at least 1.25 m wide. In special buildings this only applies if there are no concerns about rescuing people. Schools and assembly venues require two structural escape routes.
What does the app show when a stairwell fails?
The pill “Fire in stairwell A” takes that stairwell out of the calculation, the map recalculates and the line of light leads to the second route. Red areas are no violation here, because § 28a sets no length limit for the second route. The app only shows routes; it does not simulate smoke or crowds.

Subject: Architecture & scenography

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