Flood risk assessment for garden room — overkill?

Applied for a garden room/office (2.5m high, 15m2 floor area, flat roof). It's in our back garden, well away from any watercourses.

The council has come back saying we need a flood risk assessment because the property is in Flood Zone 2. But the house itself has been here since 1960 and never flooded. The garden room would be at the same ground level as the house.

A flood risk assessment costs £800+. For a glorified shed, this feels ridiculous. Is there any way to challenge this requirement or get a simpler screening?

You can request a "sequential test" exemption if you can demonstrate that the garden room is above the predicted flood level and doesn't increase flood risk elsewhere. This is much simpler and cheaper than a full FRA.

Also, Flood Zone 2 only has a 0.1% annual probability of flooding (1 in 1,000 year event). For a small garden room, requiring a full FRA is massively disproportionate. Push back hard on this.

Hadn't heard of the sequential test exemption. We'll push back with that. Cheers.