Single Stair Residential Buildings

Why Refusals Happen and What to Do About It

Single stair design is back in the conversation. Permitted development changes and urban densification mean more developers are looking at compact residential buildings where a single escape stair is the only practical option. The problem is that applications relying on single stair arrangements keep getting refused, often for reasons that could have been addressed before the drawings went in.

Here's what's going wrong, and how to fix it.

The refusal isn't always about the stair

Most single stair refusals aren't really about the stair itself. They're about the supporting fire strategy not making the case clearly enough. Building control bodies and local planning authorities aren't opposed to single stair in principle, BS 9999 explicitly accommodates it within defined parameters. What they won't accept is an assertion that it works without the engineering rationale to back it up.

If your fire strategy says "single stair is acceptable" without explaining why the building's risk profile supports it, expect pushback.

What BS 9999 actually requires

BS 9999 takes a risk-profile approach. Building height, occupancy type, travel distance, and the characteristics of the occupants all feed into whether a single stair arrangement is defensible. The standard sets out the conditions under which simultaneous evacuation from a single stair is viable, and where it isn't.

The common failure points are travel distance from the furthest point of a flat to the stair enclosure, lobbying arrangements, and the assumption that stay put applies when the risk profile doesn't support it. Getting any one of these wrong undermines the whole strategy.

The lobby question

Protected lobbies are often where single stair schemes fall apart at design stage. Architects want to maximise net internal area. Lobbies cost space. The temptation is to minimise them or argue they aren't needed. In many single stair configurations, they are needed both to protect the stair from smoke ingress and to satisfy the travel distance requirements within the flat.

Getting the lobby design right early saves significant abortive work later.

What a good fire strategy does differently

A fire strategy that supports a single stair application needs to do three things well. First, it needs to demonstrate that the building's risk profile falls within the parameters BS 9999 sets for this approach, not assume it. Second, it needs to address evacuation management explicitly, including how residents are informed and what the evacuation strategy actually is. Third, it needs to show that the passive fire protection elsewhere in the building, compartmentation, fire doors, service penetrations, is robust enough to make the strategy work in practice.

The stair is only one component. The strategy has to hold together as a whole.

The earlier the better

The worst outcomes happen when fire engineering input comes after planning. By that point, floor plates are fixed, lobby positions are fixed, and the stair geometry is fixed. If any of those need to change to make a single stair arrangement work, the cost and delay are significant.

Bringing a fire engineer in at RIBA Stage 1 or 2 isn't a luxury on schemes like this. It's the difference between a viable application and an expensive revision.

If you want a single stair design to work, the fire strategy needs to earn it, not just assert it. That's what we do.