- Project plans
- Project activities
- Legislation and standards
- Industry context
Last edited 06 Oct 2020
Alternating tread stair
Approved document K, Protection from falling, collision and impact, defines an alternating tread stair as:
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.
 Find out more
 Related articles on Designing Buildings Wiki
Featured articles and news
Air rights for developing above existing properties.
New national seismic hazard maps for the UK.
Six technologies guiding O&M into the future.
Homes carved from sandstone cliffs in England.
A review of the HES pilot project.
Organisation alerts membership to findings of IHBC research.
Four outstanding professionals recognised.
Sustainable flooring from super strong grass.
Organisation presents reactions from industry leaders.
New infrastructure bank to be based in the North of England.
Fairer, faster, greener. A summary of the key points.
Strategies to help provide safer working conditions.
Protecting flora, fauna and the other natural features of Scotland.