Strip foundation
Foundations provide support for structures, transferring their load to layers of soil or rock that have sufficient bearing capacity and suitable settlement characteristics.
Very broadly, foundations can be categorised as shallow foundations or deep foundations. Shallow foundations are typically used where the loads imposed by a structure are low relative to the bearing capacity of the surface soils. Deep foundations are necessary where the bearing capacity of the surface soils is not adequate to support the loads imposed by a structure and so they need to be transferred to deeper layers with higher bearing capacity.
Strip foundations (or strip footings) are a type of shallow foundation that are used to provide a continuous, level (or sometimes stepped) strip of support to a linear structure such as a wall or closely-spaced rows of columns built centrally above them.
Strip foundations can be used for most subsoils, but are most suitable for soil which is of relatively good bearing capacity. They are particularly suited to light structural loadings such as those found in many low-to-medium rise domestic buildings - where mass concrete strip foundations can be used. In other situations, reinforced concrete may be required.
Older buildings may have brick strip foundations.
Very broadly, the size and position of strip foundations is typically related to the wall’s overall width. The depth a traditional strip foundation is generally equal to or greater than the overall wall width, and the foundation width is generally three times the width of the supported wall. This results in the load being transmitted at 45º from the wall base to the soil.
Approved document A of Building Regulations defines minimum widths for strip footings based on the type of ground and load-bearing wall, although it is generally advisable to consult a structural engineer when designing foundations.
The underside of strip foundations should be deep enough to avoid frost action; for example, at least 450 mm unless they are bearing on rock, and at least 1 m on high shrinkage clays.
Deep strip foundations may be necessary where soil with a suitable bearing capacity is deeper.
Wide strip foundations may be required where the soil is soft or of a low bearing capacity, so as to spread the load over a larger area. Wide strip foundations will typically require reinforcement.
Where there are higher localised loads, such as columns, pad foundations may be used. See pad foundations for more information.
Where ground conditions are poor, settlement is likely, or where it may be impractical to create individual strip or pad foundations for a large number of individual loads, raft foundations may be used. See Raft foundations for more information.
Where the bearing capacity of the surface soils is not adequate to support the loads imposed by the structure, deep foundations such as pile foundations may be used. See Pile foundations for more information.
Larger or more complex buildings may involve the use of a number of different types of foundation.
Additional guidance is available in BRE's Simple foundations for low-rise housing: 'rule of thumb' design.
[edit] Find out more
[edit] Related articles on Designing Buildings Wiki
- Building foundations
- Raft foundation
- Pad foundation
- Pile foundations
- Trench fill foundation
- Types of excavation
- Bearing capacity
- Brick strip foundation
- Approved Document A
- Stepped foundation
- How deep should foundations be
- Footings in foundations
- Types of pad foundation
- Reinforced concrete
- How to design a pad foundation
- Driven piles
- Building regulations
- Rubble trench foundation
- Subsoil
IHBC NewsBlog
IHBC FREE CPD Boost - Easy Access Webinar from Historic England and the IHBC
'Enhancing conservation areas & townscapes with S.215s', 13 December - numbers limited so book now!
IHBC Out of Context - CPD check-up and prize
‘Who said that and what would you say back? FREE BS7913 for the best responses…
IHBC CPD boost: bite-sized briefings
‘Periodically’, Bob Kindred’s bite-sized briefings from the best of current heritage handbooks.
IHBC CPD Green Issue QuickQuiz
Do you know the ABCs of EPCs?
IHBC CPD Green Issue QuickQuiz Part 2
Do you know the ABCs of EPCs? - The answers! You tested your knowledge on energy performance certificates (EPC’s) in the last Newsblog so now see how well you did!
IHBC at Listed Property Show London 2019 – FREE CPD
4 hours free CPD via IHBC and partners + lots more at the show in association with Historic England, on 9-10 February 2019 at London’s Olympia.
IHBC launches new Toolbox Guidance Note for small traders
IHBC’s latest Guidance Note in our Toolbox aims to provide sole practitioners and small traders with advice on taking on new work, offering ‘Ten Red Flags’ to watch out for.
Scotland - Historic Environment Audit (SHEA) 2018 is now out
HES lead officer, Karen Robertson, has offered her personal blog looking at the trends and findings.
Slate Landscape of North-West Wales - preferred UNESCO World Heritage Site
The Slate Landscape of North-West Wales will be the UK’s next preferred nomination for UNESCO World Heritage Site status, Heritage Minister Michael Ellis announced recently.
Draft Parliamentary Buildings (Restoration and Renewal) Bill for Palace of Westminster
The draft Bill has been presented to allow ‘interested parties the opportunity to consider the approach taken to the governance of the Restoration and Renewal Programme’.
APPG for Healthy Homes & Buildings White Paper published
The White Paper highlights ‘the need for a holistic approach to building design and renovation’.
Register English Community Assets on CAsE and you could win £100 gift voucher
The Architectural Heritage Fund (AHF) asks if you own or manage a community asset that you register it on the new Community Assets Exchange - you could win £100 gift voucher.
North of Tyne gets £600m devolution deal
Northern Powerhouse minister Jake Berry has confirmed a £600 million devolution deal for the North of Tyne. It is expected to generate £1.1 billion for the local economy.
Fifteen projects reach final of Heritage Angel Awards Wales
Fifteen outstanding examples of heritage achievement have been selected for a Heritage Angel Award by a panel of judges headed by Baroness Kay Andrews.
Entries open for 2019 John Betjeman award: Closing 26 Feb 2019
SPAB invites nominations for the award celebrating excellence in the repair to specific elements of places of worship of all denominations and faiths in England and Wales.
Civic Voice: Guidance tool for communities to identify local heritage assets
A resource developed as part of Civic Voice’s Big Conservation Conversation and their ‘Local Heritage List’ campaign.
The economic value of culture - a benefit transfer study on museums in England
New research has been published to help understand the visitor and non-visitor value of cultural engagement at 4 cultural institutions in England – is this transferrable?
Former housing minister Nick Raynsford issues warning on planning
He writes that it has been reduced to a ‘chaotic patchwork’ of responsibilities which is not compatible with promoting the health, wellbeing and civil rights of communities.
DCMS revises - Principles of Selection for Listed Buildings
The Department for Digital, Culture, Media and Sport (DCMS) has issued its revised ‘Principles of Selection for Listed Buildings’ with new dates, definitions and more.
Specialist contractors call for government regulation of the construction industry
The chairman of the Specialist Engineering Contractors’ (SEC) Group wants to government to set up a statutory authority to regulate construction industry practice.
Brexit skills shortages - survey
Add your company’s take to the largest-ever poll on Brexit skills shortages.
Slow progress on encouraging female apprentices to construction industry
With 88% male in 2016/17 industry initiatives to encourage young women to join the construction industry do not appear to be making much headway.
Water-jet cutting of stone changes the industry, but only so far!
Nuclear archive wins Andrew Doolan Best Building in Scotland Award for 2018
A national archive for the civil nuclear industry by Reiach & Hall Architects has won a top Scottish architecture prize: the Andrew Doolan Best Building in Scotland Award for 2018.