Capping beam
Pile foundations are a type of deep foundation. They are formed by long, slender, columnar elements typically made from steel or reinforced concrete, or sometimes timber. A foundation is described as 'piled' when its depth is more than three times its breadth.
Pile foundations are principally used to transfer loads from superstructures, through weak, compressible strata or water onto stronger, more compact, less compressible and stiffer soil or rock at depth. They are typically used for large structures, and in situations where soil is not suitable to prevent excessive settlement.
Piles can be used individually to support loads or grouped and linked together with a reinforced concrete cap.
Pile caps can also be linked together with reinforced concrete to create a capping beam. At least three capped piles are needed to ensure stability against lateral forces (with the exception of caisson piles). Capping beams are also suitable for distributing the weight of a load-bearing wall, or of close-centred columns to a line of piles.
This differs from a ground beam which is provided between adjacent pile caps as a structural element to improve the stability of the foundation. For more information, see Ground beams.
Piles may be staggered along the beam to allow for any eccentricities that may occur in loaded conditions. If light loading is expected to result in only minor eccentricities, then the piles can be driven in a line beneath the capping beam’s centre.
The capping beam should be kept clear of the ground where the purpose of the piles is to overcome the problem of the subsoil swelling and shrinkage. This can be done by casting the capping beam on polystyrene or other compressive material, thereby allowing an upward ground movement without damage to the beam.
An economical construction method that can be adopted is to construct concrete block walls to the exact sizes of the cap. Having first backfilled the wall with soil the space can then be filled with concrete. This cuts down on the need for formwork and the extra excavation required to position it.
[edit] Find out more
[edit] Related articles on Designing Buildings Wiki
Featured articles and news
A transformative shift in the design, construction and management of built assets.
Apprenticeship announcement by the Prime Minister
Welcomed but with call for more actionable detail.
Heat pump announcements, what homeowners need to know
An 'ultimate guide to heat pumps' from a heating company.
Construction contract awards reach 7.1bn in February
Their highest level in seven months.
The journey to sustainability in heritage
Research is the key to better understanding.
Heritage approaches to adaptation, mitigation and loss.
Bridging the gap between policy, finance and installation.
Development on brownfield land
Definition, background, policy and the latest consultation.
With the Design Framework for Building Services.
Retrofit of Buildings, a CIOB Technical Publication
Pertinent technical issues, measures and the roles involved.
ECA joins HSE campaign to support mental health
Working Minds’ five simple steps based on risk assessment.
Mental health in the construction industry
Mental health issues in brief with related articles.
Transitional arrangements, Building Control and the BSR.
For pre-October buildings with substantial progress by April.
Why quality counts in domestic ventilation systems
From products, to systems to the installation.
Empowering the Future with CIOB Academy
Lifelong learning, upscaling, and reskilling for the built environment.