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
The benefits of writing articles for your organisation
How to create a profile for your organisation and publish for free.
No Falls Week. The importance of safe working at height
What to expect and what is on offer to avoid accidents.
Scottish Government action to reach net-zero targets
Retrofit expert group highlight critical actions needed.
A forward thinking, inclusive global community of members.
From engineered product life-spans, to their extension.
Circular economy in the built environment
A brief description from 2021. Where are we now?
Mental Health Awareness Week with ABS
Architects Benevolent Society programme of activity.
CLC publishes domestic retrofit competency framework
Roadmap of Skills for net zero.
May 13-19: Moving more for our mental health.
Understanding is key to conservation.
Open industry engagement survey seeks responses
Institutions and the importance of engagement.
National Retrofit Hub unveils new guide
Digital Building Logbooks and Retrofit: An Introduction.
Enhancing construction site reporting efficiency
Through digitisation and the digital revolution.
Noise in the built environment
BSRIA guide TG 20/2021.
17,000 people suffer conditions as a result of exposure to excessive noise at work.
Turning down the noise: Auditory health
A pervasive risk with far-reaching consequences.
Getting the most out of heat pumps and heating
How heat pumps work and how they work best.
Electrotechnical excellence, now open for entries.