Dry land

Much of Lagos, including parts of Ikoyi, Lekki and Ajah, was swamp before it was filled and built up. Adverts therefore say "dry land" to tell buyers that a plot is firm ground, not a swamp still waiting to be filled.

Why it matters for building. Swampy ground usually has weak soil. Structural engineers say that building on it calls for a soil investigation and piled or raft foundations that carry the load down to firm sand, and that the foundation is the biggest extra cost. Many developers avoid swamp for that reason, while low prices draw some buyers in. Houses on poorly prepared swampy plots in parts of Lagos have tilted, cracked or sunk.

Soil investigation. Lagos lists a subsoil investigation report among the documents for building approval. It records soil types, groundwater and bearing capacity, and it guides the foundation design. Even on dry land, the report tells you what foundation your building needs; weak clay layers can sit under firm-looking ground.

Reclamation rules. Lagos suspended all land reclamation projects over flood and erosion risks, requiring developers to resubmit approvals and new projects to complete full environmental impact assessments. The order followed a federal moratorium on shoreline reclamation along the Lagos lagoon. We could not confirm whether the suspension has since been lifted, so a swamp plot that still needs filling carries real regulatory risk.

Dry is not flood-free. "Dry land" describes the ground, not the flood risk. The national flood outlook lists both Lagos and Ogun among the states expected to flood, so a firm plot can still sit in a flood path or beside a blocked drainage channel.

• Lagos: the coastal belt along the lagoons, from Lekki and Ajah eastwards, has many low-lying plots near wetlands and floodplains, so adverts often stress "dry land". Parts of the mainland, such as Yaba and Gbagada, also have swampy pockets.
• Ogun: Ogun is also on the national flood list, so check riverside and low-lying plots as carefully as in Lagos.
• Everywhere: a seller's "dry land" is a description, not a certificate. Your own visit and a soil test are the evidence.