Before you build a bunker, build the right brief.

Define the intended use

Identify the occupants, duration and specific scenarios. A room designed for a short power cut is different from a specialist protective shelter. Avoid generic claims that a structure is “disaster-proof” or “radiation-proof”.

Commission a site assessment

Bring in appropriately qualified engineers and designers to assess ground conditions, the water table, flooding, drainage, existing foundations and structural loads. Excavation can affect your neighbours as well as your own property.

Design life safety as a complete system

Ask how safe escape, ventilation, fire protection, sanitation, water, power and communication work together. Specialist filtration or protective claims need competent design and verification for the intended hazard.

Check permissions before commissioning work

Planning and building-control requirements depend on location and scope. New basement excavation is likely to need planning consideration, and building regulations address structural and life-safety issues. Conservation, listed-building and party-wall issues may also matter.

Plan to maintain it

Include inspection, servicing, consumables and rehearsals in the budget. Consider whether a more resilient ordinary home or alternative accommodation better fits your risks and budget.