The short version

Homes typically become vacant first (nobody living there), then become derelict when time + exposure + unresolved barriers allow the building to fall into a ruinous or dangerous condition.

1) Ownership and legal “stuckness”

• Probate delays after the owner dies can leave a property in limbo for years.
• Multiple heirs, family disputes, or absent owners (including emigration) can block a decision to sell, rent, or repair.
• Identifying the true owner can be difficult where title/registration is incomplete or unclear.

2) Economics: renovation cost, finance, and risk

• Repair costs can exceed the market value, especially for badly deteriorated buildings or in weaker markets.
• It can be hard to secure finance for properties that are not mortgageable until major works are completed.
• Cost uncertainty (hidden defects, structural issues, compliance and fire safety upgrades) leads to deferral.

3) Planning, regulation, and delivery constraints

• Planning uncertainty, repeated permissions that don’t commence, and feasibility issues can stall reuse.
• Older buildings can require specialist work; protected structures / conservation constraints can increase complexity, time, and cost.

4) Use-pattern drivers (vacant but not necessarily derelict)

• Rental turnover, upgrades, and landlord exit/entry can create medium-term vacancy.
• Properties may sit empty while renovations are planned, funded, or paused.
• Second homes and seasonal use can increase long periods of non-occupation in some areas.

5) Weak incentives and slow enforcement (why vacancy becomes dereliction)

• Dereliction enforcement is often a slow, last-resort process; sites can remain unresolved for long periods.
• It can be difficult to prove “derelict” (as distinct from merely “vacant”), and local authority resources vary.