Where the stairs go is one of the first decisions in any loft conversion, and one of the hardest to change later. The staircase decides how much space you lose on the floor below, how much headroom you have on the way up, and how the new room fits into the fire escape route through the house.
This guide covers the three usual positions, what each one takes from the floor below, the headroom and stair types that Building Regulations allow, and how the escape route shapes the choice. If you are planning a project, our loft conversion services across West Sussex page explains how we work.
Where can the stairs go in a loft conversion?
The stairs in a loft conversion usually go in one of three places: directly above the existing staircase, off the first floor landing, or up from part of a bedroom. The right position is the one that gives enough headroom at the top, keeps the escape route protected and costs the least useful floor space below.
Two things fix the shortlist before anything else. The first is where the loft has enough height for someone to arrive at the top of the stair, which usually means near the ridge or under a new dormer. The second is where the stair can start on the first floor without blocking doors or cutting a room in half. A survey of the loft and the floor below answers both, and the design drawings then test each option against the regulations.
Can the new stairs go over the existing staircase?
Yes, and where the space allows it this is usually the most efficient position. The new flight sits directly above the existing one, so it uses space that is already given over to a staircase rather than taking it from a room. It also continues the existing stairwell, which keeps the escape route in one line from the loft to the front door.
Stacking the stairs this way depends on the roof. The top of the new flight has to arrive where the loft is tall enough, so the direction of the existing stair and the line of the ridge both matter. Where the top of the flight falls under the low part of the roof slope, a dormer above the stair is a common way to gain the height. A short turn or a few winder treads at the top or bottom can also bring the flight round to where the headroom is.
Can the stairs come up from the landing?
Yes. Where the first floor landing is large enough, the new stair can rise from it, either in line with the existing stair or turning off it. This keeps the stair in the circulation space, so it does not cut into a bedroom, and it stays within the route people already use to reach the front door.
The landing has to keep working as a landing once the new stair is in. Approved Document K asks for a landing at the top and bottom of every flight, at least as wide and as long as the narrowest width of the flight, and kept clear of permanent obstructions. Bedroom and bathroom doors around the landing still need to open, and a door may only swing across the landing at the bottom of a flight if it leaves at least 400mm clear, as shown in Diagram 1.8. On a small landing, this option often means losing an airing cupboard or a storage cupboard to make room for the first few treads.
Can the stairs go up from a bedroom?
Yes, but it usually costs the most floor space. Where the existing stairwell and landing cannot take the new flight, the stair can rise from the edge of a bedroom. Because the escape route from the loft must not pass through a room, that part of the bedroom is normally walled off and joined to the landing.
The result is a new section of corridor with the stair in it, enclosed by fire-resisting partitions and reached from the landing rather than from inside the bedroom. The bedroom gets a little smaller and its door may move. On a larger bedroom this can be a fair trade for a whole new room upstairs. On a small bedroom it can leave a room that is only usable as a study or dressing room, so it is worth weighing the space you gain in the loft against the space you lose below.
How much space does each option take from the floor below?
The floor space a loft stair takes depends on where it starts. A stair over the existing staircase takes the least, because the space is already a stairwell. A stair off the landing takes some circulation or cupboard space. A stair from a bedroom takes the most, because part of a room becomes corridor.
| Position | Where the space comes from | What to check |
|---|---|---|
| Over the existing stairs | The void above the existing stairwell, plus a small area at the bottom of the new flight | Headroom where the top of the flight meets the roof slope; a dormer may be needed |
| Off the landing | Part of the landing, often an airing cupboard or storage cupboard | Landing size at the bottom of the new flight; door swings; access to the bathroom and bedrooms |
| From a bedroom | A strip along one side of the bedroom, walled off to join the landing | How usable the bedroom is afterwards; door positions; light from the existing window |
The shape of the stair changes these numbers too. A straight flight needs the longest run in plan. A stair with winders or a quarter landing turns the corner and fits into a shorter space. A space-saver stair is the most compact of all, but Building Regulations only allow it in limited cases, covered below.
How much headroom do loft stairs need?
Approved Document K asks for at least 2m of clear headroom above a stair, measured vertically from the pitch line. For loft conversions in houses, where there is not enough space for 2m, it accepts a reduced headroom of 1.9m at the centre of the stair, falling to 1.8m at the side.
The pitch line is the line joining the front edges (nosings) of the treads, so headroom is measured from the stair itself, not from the floor below. The reduced figure in Diagram 1.4 applies only to loft conversions in dwellings, and only where 2m cannot be achieved. It does not apply to an alternating tread stair, which still needs 2m of clear headroom under paragraph 1.30.
Headroom over the stair is a separate question from the ceiling height of the room itself. Our guide to the minimum head height for a loft conversion explains how to measure the usable height in the loft and the ways of gaining more.
What types of stairs can you use in a loft conversion?
Most loft conversions use a conventional stair: a straight flight, or a flight that turns with winders or a landing. Approved Document K also allows space-saver (alternating tread) stairs and fixed ladders in a loft conversion, but only where there is not enough space for a conventional stair, and only for limited layouts.
For a private stair in a house, Approved Document K gives a rise of 150mm to 220mm per step, a going of 220mm to 300mm, and a maximum pitch of 42°. Twice the rise plus the going should come to between 550mm and 700mm. Every step in a flight should have the same rise and going. For existing buildings, the document says these figures should be followed unless dimensional constraints make that impossible, in which case any alternative is agreed with the building control body.
Straight stairs
A straight flight is the simplest to build and the easiest to use. It also needs the longest uninterrupted run in plan, which is why it suits the over-the-stairs position where that run already exists.
Winder stairs
A winder stair uses tapered treads to turn a corner without a full landing. Approved Document K sets out how they are measured. Consecutive tapered treads should have the same going, and where a stair mixes straight and tapered treads, the going of the tapered treads should not be less than that of the straight ones. On stairs narrower than 1m, the going is measured at the centre of the tread, and Diagram 1.9 shows a minimum tread width of 50mm at the narrow end.
Space-saver (alternating tread) stairs
A space-saver stair has paddle-shaped treads that alternate left and right, so it can be much steeper than a conventional stair. Under paragraph 1.29 of Approved Document K, it can be used only in a loft conversion, only where there is not enough space for a conventional stair, and only to reach one habitable room. That room can also have a bathroom or WC, as long as it is not the only WC in the house.
Paragraph 1.30 adds the construction rules: straight flights only, handrails on both sides, slip-resistant treads, uniform steps, and a maximum rise of 220mm with a minimum going of 220mm measured between alternate nosings. It also needs 2m of clear headroom.
Fixed ladders and spiral stairs
A fixed ladder, with fixed handrails on both sides, is allowed only for a loft conversion containing one habitable room, and only where there is not enough space for a conventional stair without altering the existing space. Retractable loft ladders cannot be used as a means of escape. Spiral and helical stairs are designed to BS 5395-2, which Approved Document K refers to.
| Stair type | Space needed | Where Approved Document K allows it in a loft conversion |
|---|---|---|
| Straight | The longest run in plan | Anywhere, within the rise, going and pitch limits for a private stair |
| Winder or quarter landing | A shorter run that turns a corner | Anywhere, with tapered treads measured and sized as in Diagram 1.9 |
| Space-saver (alternating tread) | Very compact | Only where a conventional stair will not fit, serving one habitable room plus an optional bathroom or WC that is not the only WC |
| Fixed ladder | The least | Only where a conventional stair will not fit without altering existing space, serving one habitable room |
| Spiral or helical | A small square footprint | Designed to BS 5395-2 |
| Retractable ladder | None when stowed | Not acceptable as a means of escape |
What else do the regulations say about loft stairs?
Beyond headroom and steepness, Approved Document K covers handrails, guarding and landings. Handrails sit 900mm to 1000mm above the pitch line, with one on both sides if the stair is 1000mm or wider. Guarding is needed where there is a drop of more than 600mm.
Where children under five may use the stair, the guarding should not let a 100mm sphere pass through any opening, and it should not be easy to climb. Open risers are allowed in houses as long as the treads overlap by at least 16mm and a 100mm sphere cannot pass through the gap. Approved Document K does not set a general minimum width for a stair inside a house, but the stair still has to meet every other point above, and the building control body will look at the design as a whole.
How does the fire escape route affect where the stairs go?
A loft conversion on a two storey house usually adds a storey more than 4.5m above ground, and Approved Document B then asks for a protected escape route from the loft down to a final exit. The new stair has to sit inside that route, which is why its position and the escape route are designed together.
Paragraph 2.21 of Approved Document B Volume 1 says that where a conversion creates a storey above 4.5m, the full extent of the escape route should be addressed. That means fire-resisting doors (minimum E 20) and partitions (minimum REI 30) along the route, including upgrading existing doors where necessary. Where the existing layout is open plan, new partitions are needed to enclose the escape route. Paragraph 2.23 sets out an alternative for open-plan layouts, which involves sprinkler protection to the open-plan areas, a fire-resisting partition and door separating the ground storey from the upper storeys, and separating cooking from the open-plan area.
This is where the three stair positions differ most. A stair over the existing staircase or off the landing already sits in the circulation space, so the escape route runs straight down through the house. A stair from a bedroom needs its own enclosure, joined to the landing, so it does not take the escape route through a room. The house will also need mains-powered smoke alarms with a standby power supply in the circulation spaces. Our guide to fire safety regulations for loft conversions covers fire doors, alarms and the escape route in more detail.
Does the type of loft conversion change where the stairs go?
Yes. The type of conversion decides where the full-height space is in the loft, and the top of the stair has to land there. A dormer, hip-to-gable or mansard adds height across more of the floor, which gives more freedom over the stair position. A rooflight conversion keeps the existing roof shape, so the stair usually has to arrive near the ridge.
That is why the stair and the conversion type are worked out together rather than one after the other. Our guide to the types of loft conversion explains what each one does to the roof.
Who decides where the stairs go?
The stair position is settled at the design stage, before anything is submitted. Apex works with trusted architectural partners who survey the house, draw up the options and show how each one meets Approved Documents K and B. The design is then checked by Building Control as part of the Building Regulations approval.
The homeowner makes the Building Regulations application, either to the council’s building control service or to a registered building control approver, and Building Control inspects the work as it goes. Apex builds to the approved design and works with the inspector on site.
Please note: this guide summarises the guidance in Approved Document K and Approved Document B Volume 1 for houses in England. Every house is different, and the building control body decides whether a particular design complies. Before any work starts, the homeowner should confirm the planning position with their local council and discuss any party wall matters with a party wall surveyor. Apex can prepare planning and Lawful Development Certificate applications, but it does not serve party wall notices or submit Building Control applications.
Not sure where your loft stairs should go?
The best way to find out is a look at the house. Get in touch with Apex Lofts & Construction and we will survey your loft and the floor below, talk through where the stairs could go, and explain what each option would mean for the rest of your home.
Frequently Asked Questions
Can I use a loft ladder for a loft conversion?
A retractable loft ladder cannot be used as the means of escape from a loft room, so it is not suitable for a habitable loft conversion. Approved Document K does allow a fixed ladder with fixed handrails on both sides, but only for a loft conversion containing one habitable room, and only where a conventional stair will not fit without altering the existing space.
Are space-saver stairs allowed in a loft conversion?
Yes, in limited cases. Approved Document K allows alternating tread (space-saver) stairs only in a loft conversion, only where there is not enough space for a conventional stair, and only to reach one habitable room, with an optional bathroom or WC that is not the only WC in the house. They need handrails on both sides and 2m of clear headroom.
How steep can loft conversion stairs be?
For a private stair in a house, Approved Document K gives a maximum pitch of 42°, with a rise of 150mm to 220mm and a going of 220mm to 300mm per step. Space-saver stairs can be steeper because their treads alternate, which is why they are only allowed in limited cases.
Can a loft conversion have a spiral staircase?
Yes. Approved Document K refers spiral and helical stairs to BS 5395-2, and they can work where floor space is tight. The stair still has to give enough headroom and fit into the protected escape route, so its position is checked against Approved Document B as well as the stair standard.
Do the new loft stairs have to match the existing staircase?
No. The Building Regulations deal with safety, not appearance, so there is no requirement for the new flight to match. Where the new stair sits directly above the existing one, many homeowners choose matching balustrades and handrails so the two flights read as one staircase, but that is a design choice.
Does Apex Lofts & Construction design the staircase?
Yes. We work with trusted architectural partners who survey the house and draw up the stair options as part of the loft design. The homeowner makes the Building Regulations application, and Building Control checks the design and inspects the work. We build to the approved drawings and work with the inspector on site.