Alternating tread stair
Approved document K, Protection from falling, collision and impact, defines an alternating tread stair as:
A stair with paddle-shaped treads where the wide portion is on alternate sides on consecutive treads.
In dwellings, alternating tread stairs may only be used in loft conversions where there is not enough space for conventional stairs and where the stair is for access to only one habitable room and, if desired, a bathroom and/or a WC (although this must not be the only WC in the dwelling).
Alternating tread stairs should:
- Make alternating steps uniform with parallel nosings.
- Have slip-resistant surfaces on treads.
- Should be constructed so that a 100mm diameter sphere cannot pass through the open risers.
- Provide a minimum clear headroom of 2m.
- Have tread sizes over the wider part of the step in line with the table below, and should comply with the diagram below.
 Related articles on Designing Buildings Wiki
Featured articles and news
Eleven Magazine announce the winner and runners-up in their Moontopia competition.
As January is the time for hitting the gym, Designing Buildings Wiki lists the best gym architecture in the world.
London is at the top of the list of global construction megacities, beating Dubai and Abu Dhabi.
What are the innovative business models of the future, and how to incentivise supply chains to work on a whole life basis?
One of the largest churches in the world, the monumental St. Peter's Basilica.
How thermal comfort is quantified and how it can affect wellbeing.
Snøhetta complete a treehouse cabin that allows guests to lie beneath the Northern Lights.
Christiania is an anarchist 'freetown' in Copenhagen where strange and experimental architecture has flourished.
“UK waste data needs improving” say BRE specialists, in this summary of their report into construction waste.
UandI announce new joint venture with US developer to work on office refurbishment projects.
Why buildings crack, how cracks are categorised and what can be done.