The staircase is one of the most important — and most often underestimated — design decisions in a loft conversion. A new stair to the loft creates a new route vertically through the house, but it also takes space from the floor below. Where that floor area comes from, and how it affects the layout of the existing bedrooms or landing, is a decision that can significantly change how well the finished project works for the household.
The most common approach in a London terraced house is to extend the existing first-floor landing to accommodate the new stair. The landing is widened or extended rearward, typically taking a portion of the rear first-floor bedroom. The new stair rises from this extended landing area to the loft. The floor area taken from the rear bedroom is typically two to four square metres — enough to add a small alcove or landing at the cost of a slight reduction in the bedroom behind it. Whether this is acceptable depends on the existing size of that bedroom.
In houses where the first-floor layout positions the staircase directly below the point where the loft stair will land, it is sometimes possible to build the new stair in the same vertical stack — rising above the existing stair. This is architecturally neat and minimises the floor area taken from any bedroom. However, it requires the geometry of the existing stair to align well with what is required above, and the head heights must work in both the existing stair and the new one.
Where neither of the above works, the stair can be positioned to rise within a bedroom, entered through a door at the base. This is sometimes the only viable solution in houses with very tight landing geometries, but it permanently changes the way the bedroom functions — typically making it a through-room from the landing to the loft rather than a standalone bedroom.
Building Regulations requirements for loft staircases are specific. The maximum pitch is 42 degrees for a standard stair. The minimum going (the horizontal depth of each tread) is 220 millimetres. The minimum rise is 155 millimetres, maximum 220 millimetres. Minimum clear headroom on the stair is 2000 millimetres, though 1800 millimetres is sometimes accepted at the oblique edge of the stair beneath a sloped ceiling. Where space is very constrained, an alternating tread staircase (also called a space-saver stair or paddle stair) is permitted in a loft conversion under Building Regulations, but only where a conventional stair is genuinely not feasible — it must be agreed with Building Control.
RCB discusses staircase options with every loft conversion client before the design is frozen, because the impact on the floor below is as important to get right as the loft design itself. 07359 872594 | contact@rcbgroup.co.uk | www.rcbgroup.co.uk