Rubble trench foundation
This is a variation of the trench fill foundation, and is a traditional construction method which uses loose stone or rubble to minimise the concrete requirement and improve drainage. It follows the same approach as a French drain, with a trench that is filled with crushed stone letting any water drain down and away from the foundation.
This approach has been used in various guises for thousands of years but it was popularised in the 20th century by the architect Frank Lloyd Wright, and has been promoted as being more environmentally-friendly than other foundation types.
The bottom of the trench should slope with an even descent of at least 3 cm for every 1 m of trench, which diverts the water towards one point, from which it can be diverted away through an outlet or to a dry well.
The trench should be lined with a geotextile material to prevent the surrounding soil from clogging up the trench and outlet. It is then filled with angular and washed stones of average size 2.5-5 cm, with them being compacted at every 30 cm layer using either a pneumatic or hand-powered tamper.
The washing of the crushed stone is important since it removes sand, silt and other small particles that could build up in the trench over time.
When it reaches around 20-30 cm below grade, the larger blocks of stone can begin to be built up as a continuous wall.
This type of trench is unsuitable for particularly expansive or poor load-bearing soils. An alternative, less eco-friendly solution, is to combine the rubble fill with a concrete grade beam.
[edit] Find out more
[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.