With this project we were contacted firstly, in an advisory capacity by the architect and his engineer. Their original plan consisted of an extension to the property and too remove the roof, and build an additional storey.
The existing foundations were exposed, to verify their suitability to carry the additional load. Although the footings complied with width and depth, the ground underneath was very wet, and the clay soft and silty. Further testing was then carried out by way of two bore holes, and the results were handed over to us.
Due to the poor ground conditions, and since the existing schemes involved alterations to the ground floor layout, the client after consultation with her architect, decided upon an alternative scheme, of complete demolition and constructing a new dwelling off, Piled foundations. The house footprint will also be shifted to avoid removing the original footings.
Before being given the the contract, we helped with pricing the ground beams and Piling. Which enabled the client to understand where her budget would be going, even before they had decided to demolish the property. Due to the nature of the ground, the high water table/springs, and the loadings of the Piles, 220mm dia Steel Cased Bottom Driven Piles were the best option.
Poor access was also an issue on this site, as it was in the middle of the New Forest, and we had to negotiate fording a river, and 2 miles of rough track, which made our steel tube, and concrete deliveries challenging.
Scope of works:
*Piling mat, Pile positions and welfare facilities, were the main contractors responsibility on this project.
*Mobilise D500 and D1000h with 7.5t lorry suited to smaller access sites.
*Locate steel tube delivery and escort them to site.
*Install 32 No 220 Steel Cased Bottom Driven Piles to design depth.
*Cast all completed Piles with C35 concrete and reinforcement to our engineers design specifications.
*Place safety tops on all reinforcement.
*Clear site of rubbish and demobilise Rigs.
The D1000h Driven Piling Rig allows us to lift the driving weight over 3.0m, this means we can weld the tubes up in front, and can continually drive Piles without stopping.
This property has 2 fire places; when we arrived onsite, 2 of the piles in the fire place were too close together, so with a quick call to our engineer we were able to move the piles apart, so they were 3.5 times the diameter away from each other.
The first load of concrete is in, reinforcement inserted and safety caps placed on all protruding steel reinforcement.
All our sites are left clean and tidy, which makes the next stage of the project a lot easier for the next contractor.
As main Piling contractor on this project we were required to provide a Contiguous Piled retaining wall, around the perimeter of the property. The property is a five storey, end terraced house in the heart of Nottinghill. The side access to the garden, was 2.5m wide which, restricted the size of Piling rig we could use onsite.
The basement on this project, will be two levels, with the first level as living quarters, and the second as plant and storage rooms. This meant that the retained depth changed where we stepped down for the double basement, so our Contiguous Pile depth ranged from 8.0 – 15.0m. And as we are a smaller company, with a hands on attitude our engineer was onsite to over see most of the Piling works which enabled us to sort out any problems quickly keeping the programme within time scale.
The whole house is to be put on a transfer slab extending the basement, beyond the footprint of the house. Which required us to install temporary Bearing Piles to take the load of the house while the basement is being excavated. There are also a number of internal and external Tension Piles and internal Compression Piles to take loadings of 200kn at sub basement level.
Scope of works:
*Site welfare and Health and Saftey set out by Main contractor.
*Mobilise T5000 Auger Rig and 300mm dia solid stem augers to reach design depth.
*Steel and safe area for making cages was set up.
*Dumper for concrete with a chute.
*Lifting frame with 110v winch to safely lower cages for Internal Piles with minimum headroom of 2.3m.
*Complete all external Contiguous piles and Tension Piles.
*Install Contiguous Piles to form sub basement, which will join up with deeper external piles.
*Install Temporary Piles which will support the transfer slab while Sub basement is being excavated.
*Install Bearing Piles with a design depth to take 200kn.
*Clear site and demobilise T5000 Auger Rig and all other equipment.
On our first visit to site our engineer checks access, and the centre lines of piles so we can decide which Rig would be most efficient onsite.
T5000 Auger Rig with outriggers and 300mm dia lead flight with a cutting head for London clay and mudstone.
All the walls had been underpinned by the main contractor, the Contiguous Piled wall had to continue between the remaining walls supporting the house which proved to be very challenging. Especially underneath the stairs to the front door, where we had to install 4 Piles, at our minimum working headroom 2.25m, which meant boring and casting 2 Piles a day.
All of the steel reinforcement for the Contiguous Piled retaining wall had, 6H16 @ 2.2m long in a H8 helical – 200mm O/D (overall diameter) and pitch of 150mm (distance between helix). The design depth for these Piles was 15.0m so we had to connect and lower 10 cages, in each open bore before casting the Pile. Our custom winch and lifting frame has a SWL of 500kg and makes this job very safe.
Contiguous Piles installed, cut and broken down ready for capping beam.
Advanced Mini Piling Systems operative, with a concrete dumper, is far more efficient than using wheel barrows, and a lot cleaner than using a concrete pump which requires a lot of water to clean, which we don’t need in the winter.
As you can see from the photo the reinforcement has not been cut down, saving the main contractor time and money when casting the capping beam. which shows we care about what we do, and we work with the client, not for them.
Part of the finished retaining wall to the basement, underneath the bay window, also acting as a fire escape.