Rules for Building Spiral Staircase

As they twist round in a tight curve they offer a very space-saving solution when accessing a different floor, taking up considerably less floor space than a conventional staircase.

In medieval times, spiral staircases were commonly located in circular castle turrets and were often constructed in stone. They were configured in a clockwise assent to give attacking right handed swordsmen a disadvantage whilst ascending.

These days spiral staircases designs have developed dramatically and whilst maintaining their space saving benefits, are manufactured in a variety of materials such as glass and stainless steel. They now offer the right property a stunning alternative to a standard staircase, becoming a stylish 'feature' of a room.

Due to their tight construction they are not overly easy for the elderly or disabled to use and moving large pieces of furniture between floors can prove tricky. For safety reasons there are currently various rules and regulations governing the size of spirals staircases installed in new builds and renovations in residential and commercial settings.

UK Building Regulations

Spiral staircases have their own 'British Standard' dedicated to them - BS 5395 part 2. The BS is referred to in Building Regulations part K and ensures the spiral staircase is large enough for the given application.

Within the document, spirals are divided into five categories, A-E with A being a secondary domestic spiral and E being a large fully public spiral. Each category dictates the relationship between the rise (height of each step) and going (depth of each step) and 'clear tread width' (the distance from the inside of the handrail to the centre column) required for the spirals' usage. Generally, the more people the spiral is providing access to, the larger diameter and the smaller the rise height, making it safer and more comfortable to climb.

Domestic Spiral Staircases

With domestic spirals there are two generally rules to adhere with - there should be no gap between the treads or the balustrade of more than 100mm, and the balustrade should not be constructed with climbable rails.

Category A and B of BS 5395 deal with the measurement requirements for domestic spiral staircases. Category A is referred to as a secondary domestic spiral and category B covers spirals used as main stairs within a dwelling.

The clear tread width of a secondary spiral should be 600mm which (depending on the specific model / design) gives a 1450mm diameter when taking into consideration the centre column and the balustrade to both sides. The height of each step should not exceed 220mm and the centre going should be at least 145mm. A spiral used as a main staircase should have a clear tread width of 800mm (1800mm diameter) and 220mm maximum rise and a 190mm minimum central going. Generally the opening in the floor for a spiral should be around 100mm larger than the diameter whether the opening is square / rectangular or circular. For example a 1600mm diameter spiral should have a 1700mm square or diameter opening. This is to allow for a 50mm 'knuckle gap' between the handrail and edge of floor / wall on both sides. The top step of a spiral staircase is normally an enlarged step which connects the centre column to the edge of the floor. This top landing platform can sometimes be shaped to allow for slightly smaller openings.

Commercial Spiral Staircases

Categories C-E of BS5395 covers the required dimensions for commercial staircases - those to be used by the public. The guidance ensures that people unfamiliar with the spiral can use it safely. With all commercial spirals staircases there is a requirement of a centre column handrail and a 'rest' platform if the flight consists of more than 16 risers.

Category C is for a small semi-public stair and has to have a rise height of no more than 220mm and a clear tread width of 800mm. The diameter of this (with the centre column handrail in place) is therefore around 1900-2000mm. Category D is for a semi public stair serving more than 50 people. The regulation looks for a minimum rises of 190mm and a clear tread with of 900mm (2100mm diameter).

Category E deals with spirals intended to be used by large number of people at one time - shopping centre or football stadium for instance. A 1000mm clear tread width is required along with a 190mm maximum rise and 250mm minimum going measurement.

The guidelines covered by BS5395 are subject to interpretation by planning offices and are not always set in stone. A relaxant is sometimes offered when, for example, one is replacing an existing spiral.

OVERVIEW

Spiral Staircases offer the right property a stunning solution when accessing an upper level. There are a vast number of different models currently on the UK market with many off-the-shelf kit solutions imported from Europe. Should you be looking to install / purchase a spiral, it is important to check with the supplier that is up to UK standards. If in doubt, check with your building control officer.