- 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
The role of HVAC systems in the safe return to work.
CLC provides guidance related to product marks, post-Brexit.
Net zero goals incorporated into plans for a new European Bauhaus.
BREEAM offers its resilient approach to Building Back Better.
Country moves one step closer to creating independent body.
BSRIA examines factors driving the industry.
Ensuring designs are developed, validated and can be effectively implemented.
The Homebuyer Survey most suitable for newer homes or simple properties.
Health and safety practices for body and mind.
28 leading bodies set out their vision for the future.
Chancellor announces latest Winter Support packages.
Tapping technology to boost infrastructure and create jobs.
4 ways to ensure certificates are valid.
White elephant construction projects.