Nuclear bunker structure: walls, doors and emergency exit

Withstand what the design states
The structure is sized on the expected loads: the ground, the building above, and the events the client decides to consider. The structural engineer translates them into thicknesses and reinforcement.

Let neither air nor water through
Joints, duct and cable penetrations, the door threshold: every crossing is a sealing point to be designed. Without airtightness there is no overpressure, and air filtration loses its purpose.

Where to build it
Underground offers natural protection and discretion, but requires excavation, waterproofing and water management. An above-ground room built into the house is simpler to build but more exposed: the choice depends on the risk and the site.

Build new or adapt
An existing cellar can become a shelter only if its shell and airtightness can be upgraded. In many cases it makes more sense to build a new room than to force an old one.

A shelter door is not a household security door: it must be airtight, strong, openable from the inside in any condition and, if desired, unrecognisable.

Seals and pressure closure
The door closes airtight against its frame, with seals that must be checked over time.

Forced entry and loads
For burglar resistance, the European reference for doors and windows is EN 1627; for strongroom and vault doors it is EN 1143-1. In Swiss-style shelters, reinforced-concrete doors are the standard solution.

Nobody stays locked in
The door always opens from the inside, even without power and even if the outside is blocked: hence the emergency exit.

Concealed door
Where discretion matters, the door can be hidden behind a bookcase, a wardrobe or a technical wall. Concealment does not replace strength.

Emergency exit.
A shelter has a second route independent of the main door: a tunnel, a hatch, a passage to another room. In Switzerland it is a standard requirement for domestic shelters: armoured closure, tunnel and shaft with a ladder opening outdoors, outside the area where the rubble of the house could fall; the shelter also draws its air from the same tunnel. In private projects it is a common-sense choice that avoids being trapped.

The route from inside.
The route from the bedroom to the shelter must be short, free of obstacles and walkable in the dark. It is tested in person, at night, before handover.

Integration with the house.
The shelter's alarm, video verification and access control are designed together with those of the home: whoever is inside the shelter must be able to see what is happening outside without exposing themselves.