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Underpinning can be used to rectify subsidence, to provide additional bearing capacity when building above an existing structure or to provide a new bearing position if deep excavations, such as those required for basements, are to be formed adjacent to an existing property.
Excavations are made beneath the existing foundations to the required depth and concrete placed leaving a space of 50mm -75mm for a dry pack material to be placed to ensure a ‘tight’ joint between the new underpin and the old foundations.
Following completion of the piling works we can carry out installation of reinforced concrete beams, pads and slabs to link the piles together and provide a platform for further superstructure construction. On most projects we use proprietary formwork and shuttering, such as Pecafil, to ensure the correct alignment for the works and maintain adequate concrete cover to the reinforcement.
If ground conditions require it we can place a ‘voidformer’ beneath to allow the underlying strata to heave without destabilising the foundations. Voidformers used include Claymaster, Cellcore or Clayboard.
The high cost of property, particularly in built up locations such as London, is prompting more clients to consider extending their existing property by excavating the land below it to form a basement. Our basement service includes design, excavation, underpinning and construction to floor slab stage, for fit-out by other contractors. Either piles or traditional underpinning can be used and in many instances occupancy can be maintained in the property above while the basement works are carried out.
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For the price of a small geotechnical study or survey you can cut the risk of the cost of the project rising above the original price quoted. It is important to establish the strata that foundations are to bear into prior to the commencement of the project to ensure the correct foundation method is utilised.
Generally the information provided by this study will enable the piling contractor or subcontractor to create a more accurate design, reducing the costs incurred by unnecessary piling length.
On domestic projects we can offer a service in which we carry out a trial bore using one of our piling rigs to establish the most suitable type of pile for a project. In many cases the fee for this service will be refunded if we are subsequently awarded the piling project.
Other forms of testing that we offer include:
- Pile integrity testing, to ensure that the piles have no cracks or voids in them.
- Pile load testing, to ensure that the piles are capable of carrying the design load. This may be either by dynamic load testing or static load testing.
- Concrete cube testing, to ensure that the concrete used on our projects has achieved its designated strength.
We can implement preliminary or working pile tests and investigate sites to establish the best, most cost-effective method of constructing foundations.
Design
We offer a design and construction service for all piling schemes.
Should you wish, we can provide a detailed engineered foundation from drawings provided by your architect for submission to the Local Authority. All design works carried out by us are backed by a £2m professional indemnity insurance.
In instances where we carry out the design of the foundations we are able to plan the scheme to suit our capabilities, ensuring we can offer a cost effective solution for your foundation needs.
Piling mat preparation
It is important in all situations to provide a suitable surface from which to carry out our piling operations. The requirement varies depending on the piling rig to be used.
We can offer the design and installation of the piling mat if required.
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