A 2025 headline suggested that more than 100,000 homes could be built in England’s highest-risk flood zones. That number needs context. It was not a list of planned developments, a count of planning permissions or a forecast that 105,000 homes would definitely be completed.
The Guardian’s analysis, published on 8 February 2025, took two figures: a government target of 1.5 million additional homes over the parliamentary term, and the reported share of new homes in Flood Zone 3 in two earlier years. The Environment Agency’s report for 2021–22 records that 7% of new homes were in Zone 3, unchanged from 2020–21. Applying that historic percentage to 1.5 million gives roughly 105,000. It is a simple scenario calculation: it assumes both that the target is achieved and that the earlier share continues. It does not account for where future sites will be chosen, planning decisions, mitigation or whether homes are completed.
Flood Zone 3 is a planning category for land with a 1% or greater annual probability of river flooding, or a 0.5% or greater annual probability of sea flooding, before taking account of flood defences. Those probabilities describe mapped areas, not the certainty that a particular building will flood in a particular year. Flooding can also come from surface water, groundwater, overwhelmed drainage, reservoirs and other sources, so a river-and-sea zone map is not a complete property-level risk check.
Government planning guidance requires flood risk to be assessed when relevant. Plans and applications use a sequential approach intended to steer development towards areas at lower risk where possible. A site-specific flood-risk assessment may be required, and the Exception Test applies in specified circumstances. If development proceeds, design and mitigation should make it safe over its lifetime without increasing risk elsewhere. Flood Zone 3 therefore does not mean every proposal is automatically refused, but it does require the risks and planning tests to be addressed.
The official 7% statistic is historical, not a current annual rate. The Environment Agency report covers April 2021 to March 2022; later national flood-risk mapping uses updated methods and describes exposure to several flood sources, which is not the same measure as the share of new addresses built in Zone 3. Readers should treat the 105,000 figure as a conditional illustration of what could follow if old patterns and the housing target both held—not as evidence that those homes have been approved or built. For a real site or home, consult current planning records and the Environment Agency’s relevant flood-risk services rather than relying on this national extrapolation.