Escape Windows in HMOs: Sizes, Positions and When They Count

Open the bedroom window during an HMO inspection and if it does not swing wide enough, sit low enough, or open freely without a key, the fire risk assessor will fail that room there and then. A failing escape window can hold up an HMO licence renewal, trigger enforcement action under the Housing Act 2004, and in the worst cases sits behind a prohibition notice that closes the room to tenants until it is fixed. None of this is complicated once you know the numbers, but landlords get caught out on this more often than almost any other single item on a fire risk assessment.

What Counts as a Compliant Escape Window

An escape window, sometimes called an emergency egress window, is a secondary means of escape for a bedroom or other habitable room that does not open directly onto a protected escape route. The dimensions come from Approved Document B of the Building Regulations, and they are specific: the openable area must be at least 0.33 square metres, and neither the height nor the width of that opening can be less than 450mm. Both conditions apply together, so a tall, narrow window that technically clears 0.33m² but is only 400mm wide still fails.

The window also has to be usable. The bottom of the openable area, the cill, must be no more than 1100mm above the floor. Any higher and an occupant, particularly a child, an older tenant or someone who has been woken by smoke in the dark, will not be able to climb out unaided. A window that meets the area and width test but has a cill at head height does not count as a valid means of escape, whatever the risk assessor's tape measure says about square metres.

This is not guidance you can round up on. Fire risk assessors working from LACORS-based HMO fire safety guidance apply these figures literally, and a window that is a few millimetres short on any one measurement is recorded as a fail, not a near miss.

The 4.5 Metre Rule: When a Window Stops Being Enough

Escape windows only work as a means of escape on lower floors. Once a room sits more than 4.5 metres above ground level, roughly the second floor and above, a window is no longer treated as an adequate escape route on its own. At that height the assumption is that most occupants cannot safely jump or lower themselves out, so the room needs a properly protected escape route instead: a fire resisting door onto a protected stairway or corridor, or fire separation that gives occupants a safe route to the final exit.

This catches out landlords converting attic or second floor rooms into extra lettable bedrooms. It is tempting to put in a roof window and call it done, but if that room sits above the 4.5 metre threshold, the window does not solve your escape problem no matter how big it is. You need a protected route through the building, which usually means upgrading doors and partitions on that floor, not the glazing.

When You Do Not Need an Escape Window at All

The escape window requirement is a fallback, not a universal rule. If a bedroom opens directly onto a protected escape route, a hallway or landing separated from the rest of the building by fire doors and fire resisting construction that leads straight to a final exit, the room does not need its own escape window, because the occupant already has a safe way out that does not depend on the room itself. This is why purpose-built flats and well-converted HMOs with a protected stairway often have bedrooms with ordinary windows and no escape window at all, and it is perfectly compliant.

The trap is assuming your corridor counts as protected when it does not. If the doors off that corridor are ordinary internal doors rather than certified fire doors with self-closers, or if the corridor also serves as a route through a room with a fire load such as a kitchen, it is not a protected route, and every bedroom off it falls back to needing its own compliant escape window. Check the corridor's fire doors and construction before you assume your bedrooms are exempt.

Position, Obstructions and Escaping Unaided

A window that opens onto a wall, a fence, railings, or a light well is not a valid fire escape even if the glass itself meets every dimension. The principle is that occupants must be able to get out and reach a place of safety without help and without obstruction. A basement bedroom with an escape window opening into a sunken lightwell surrounded by railings fails this test even when the opening is technically the right size, because nobody is climbing out and over railings while a building fills with smoke.

Furniture causes as many failures as building fabric. A wardrobe pushed in front of an escape window, a bunk bed frame that blocks the opening, or a desk permanently positioned under the sill all defeat a compliant window just as effectively as a badly sized one. Tenants rearrange rooms constantly, and a window that was clear on the day of the fire risk assessment can be blocked within a month. Make it part of your routine property checks, not just the annual assessment, to confirm nothing has been placed in front of an escape window.

Locks matter too. If an escape window needs a key to open, and that key is not kept somewhere the occupant can reach it instantly in the dark, it is not compliant. Restrictor stays and child safety catches are common in HMOs and are generally fine, provided they release quickly and without tools. Anything that needs more than one simple, obvious action to open in an emergency is a problem worth fixing before your next inspection.

Where HMOs Get This Wrong

The most common failure is not a badly sized window, it is an inner room. If a bedroom's only way out runs through another room, a shared kitchen diner used as a thoroughfare, for example, then that bedroom is treated as an inner room under Approved Document B and needs its own escape window unless the space it opens off is low fire risk, such as a bathroom or hallway with little fire load. Landlords who converted a large room into two by adding a stud wall frequently create an inner room without realising it, and without adding a second escape route to compensate.

Replacement windows are another regular trap. Original sash or casement windows in Victorian and Edwardian conversions often had generous openings, but cheap replacement windows are sometimes fitted with smaller top hung vents that never reach 0.33m², or with fixed lower panes that do not open at all. If you have replaced windows in an HMO bedroom since your last fire risk assessment on escape routes, check the openable area again before your next inspection, not after.

Basements, Attics and Inner Rooms

Basement rooms bring the obstruction problem and the 4.5 metre problem together in reverse: they are below ground, so the escape window has to open onto something an occupant can actually climb into and then out of, such as a lightwell with a ladder or steps, not just up against a solid retaining wall. If that is not achievable, the basement room needs an alternative protected escape route instead of relying on a window at all.

Loft conversions used as bedrooms need the height check done properly, measured from the actual floor level of the room, not the roofline. A loft bedroom is very often above the 4.5 metre mark once you measure from the room's floor to the ground outside, which means a roof window alone will not satisfy a fire risk assessor, however large it is.

Recording It Properly in Your Fire Risk Assessment

A verbal confidence that "the windows are fine" will not survive a licensing inspection or an insurance claim. Measure and record, room by room: the openable width and height, the calculated area, the cill height above the finished floor, and the drop height to ground outside. Photograph each window in its open position alongside a tape measure, and keep that evidence with your written fire risk assessment rather than as loose photos on a phone that gets replaced in two years.

Repeat the check whenever anything changes. New windows, a loft conversion, a stud wall that creates an inner room, or a tenant's own furniture rearrangement are all reasons to re-measure rather than rely on figures from the last full assessment. Under Building Safety Act 2022 section 156, every responsible person must hold a written fire risk assessment regardless of the size of the HMO, so there is no threshold below which you can skip this and rely on memory instead.

If you are not certain every bedroom window in your HMO meets all three measurements and sits below the 4.5 metre threshold with a clear, unobstructed drop, measure them before your next fire risk assessment rather than during it. FRASafe guides you through a BS 9792:2025-aligned fire risk assessment, with a PDF report for £45. It flags escape window issues room by room so you can fix them before a fire officer or licensing inspector does it for you.