Threshold
A threshold is a strip of wood, stone metal and so on that forms the bottom of a doorway, which is crossed when in entering a building or a room. It is sometimes referred to as a door sill or door saddle.
Thresholds can pose a barrier to passage for people with disabilities, and so thresholds are now typically level, rather than stepped, with a level or ramped approach. However, this can create difficulties preventing water penetration or air infiltration through a doorway from the outside, and so modern threshold designs can be complex.
An ‘accessible threshold’ is defined as a threshold that is level or, if it is raised, has a total height of not more than 15mm, a minimum number of upstands and slopes and with any upstands higher than 5mm chamfered.
Other acceptable solutions are described in ‘Accessible thresholds in new housing – Guidance for house builders and developers’, The Stationery Office Ltd. 1999.
Ref Approved document M, Volume 1: Dwellings.
The word threshold can also refer to a level at which a change applies, for example; the payroll threshold above which the apprenticeship levy applies, a size of project above which an Environmental Impact Assessment might be required, the threshold for appointment of principal contractors and principal designers, the temperature threshold above which overheating might occur and so on.
[edit] Related articles on Designing Buildings Wiki
Featured articles and news
Deputy editor of AT, Tim Fraser, discusses the newly formed society with its current chair, Chris Halligan MCIAT.
Barratt Lo-E passivhaus standard homes planned enmasse
With an initial 728 Lo-E homes across two sites and many more planned for the future.
Government urged to uphold Warm Homes commitment
ECA and industry bodies write to Government concerning its 13.2 billion Warm Homes manifesto commitment.
Places of Worship in Britain and Ireland, 1929-1990. Book review.
The emancipation of women in art.
CIOB Construction Manager of the Year 2025
Just one of the winners at the CIOB Awards 2025.
Call for independent National Grenfell oversight mechanism
MHCLG share findings of Building Safety Inquiry in letter to Secretary of State and Minister for Building Safety.
The Architectural Technology Awards
AT Awards now open for this the sixth decade of CIAT.
50th Golden anniversary ECA Edmundson awards
Deadline for submissions Friday 30 May 2025.
The benefits of precast, off-site foundation systems
Top ten benefits of this notable innovation.
Encouraging individuals to take action saving water at home, work, and in their communities.
Takes a community to support mental health and wellbeing
The why of becoming a Mental Health Instructor explained.
Mental health awareness week 13-18 May
The theme is communities, they can provide a sense of belonging, safety, support in hard times, and a sense purpose.
Mental health support on the rise but workers still struggling
CIOB Understanding Mental Health in the Built Environment 2025 shows.
Design and construction material libraries
Material, sample, product or detail libraries a key component of any architectural design practice.
Construction Products Reform Green Paper and Consultation
Still time to respond as consultation closes on 21 May 2025.
Resilient façade systems for smog reduction in Shanghai
A technical approach using computer simulation and analysis of solar radiation, wind patterns, and ventilation.