Groundwork refers to work done to prepare sub-surfaces before work is undertaken directly on the land.
Aside from demolition and site enabling works, groundwork are usually the first stage of a construction project that may include some of the following undertaken by groundwork contractors:
- Ground investigation
- Site clearance
- Substructure and ground stabilisation works
- Site services
Before groundwork can be put into action, most local authorities require a legal ground investigation, which aims to identify past usage, stabilities and where they may have to overcome problems. This allows data to be accumulated and used for effective design, and eliminates the risk of building on unsuitable land – such as old mines and contaminated sites.
Clearing the site is an import part of the initial preparation phase. The top soil needs to be taken up from the footprint of the structure, of which the depth will be dependent on the lay of the land, for example, how much of a slope it is measured to be. Where necessary, retaining walls may be constructed to develop level development platform that can then be built on.
Substructure is defined by the RICS as ‘All work below underside of screed, or where no screed exists, to underside of lowest floor finishes that includes damp-proof membrane. Retaining walls are used, which structures are made from stone, brick or block-work that are reinforced with concrete or timber.
Basement excavations are sometimes used, which is a relatively cheap method of retaining wall construction. This involves huge use of large scale hydraulic jack hammer equipment to drive steel sheet piles into the ground and have the structures interlocked, forming a continuous wall.
Soft nails, ground anchors and geo-synthetic materials are all used to achieve such a structure that can then be proceeded to continue to the next phase of construction. Foundations are essential to for the supporting of structures, which allows transfers the load to layers of soil and rock that have sufficient bearing capacity and suitable settlement characteristics. There is a large range of foundation types that make it suitable for different applications, which depends on considerations such as:
- Required support for load
- Ground conditions and capacity
- Presence of water
- Sensitivity to noise and vibration
The foundations will range from shallow to deep, dependent on the above factors. Good construction and groundwork contractors will ensure the most appropriate services are employed.
Existing services should be altered to ensure it will be suitable for the new construction, while land that has no previous water or electric supply must be laid out. Site services may include permanent drainage and other utilities connections.