Warning: this is a long read, up to you if you read on!
The club has shared a number of excellent photos and videos of the redevelopment works, but there has been relatively little explanation of the construction process behind them.
With work now progressing on the corner stands and the South Stand set to follow shortly, I thought some posters might be interested in some background reading to provide additional context on what we're seeing take shape on site.
I’m not particularly interested in the hospitality fit-out, the new pitch or the players’ tunnel. For me, it’s the stands that are the most exciting part of the redevelopment, so that’s what I’ll focus on here.
At the moment, all eyes are on the corner stands, with foundation works well underway and the the above-ground structure hopefully not too far behind. With that in mind, I thought I’d take a
closer look at the substructure works, and perhaps do something similar once we start to see the frame emerging above ground.
With the caveat that I'm piecing this together from the planning documents, what can be seen from around the site perimeter, and the occasional drone video, this is my best interpretation of the works taking place and the process behind it….
Purpose of foundations
So, why do the stands need foundations?
Stating the obvious, but the main purpose of foundations is to safely transfer the loads from a structure into the ground. Without suitable foundations, the new stand structures wouldn’t last very long.
Types of foundations
For smaller stadium structures founded on good ground, you might expect relatively shallow foundations, such as strip or pad foundations. For larger structures, or where ground conditions are less favourable, deeper foundation solutions such as piles will be required to transfer loads to more ‘suitable’ ground at depth.
Ground / Geotechnical Investigation (GI)
To help determine which foundation solution was required, a team of engineers completed a site investigation in 2025 to gather geological and historical information about the site.
The investigation included a number of trial pits and cable percussion boreholes across the site. These techniques involved excavating and drilling into the ground to understand the type, strength and density of the ground at different depths. Material samples were also collected for lab testing to provide further information on soil characteristics and to identify any ground contaminants and associated construction risks.
The locations of these investigations are marked up on the image below (TP = trial pit, CP = cable percussion borehole) and would have been selected to provide a good spread of information across all four stands and corners.
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Superstructure
So, what are the foundations actually supporting?
The foundations form part of the ‘substructure’ and are designed to support the ‘superstructure’ - everything that sits above ground level. In the case of the new stands, this includes the structural steelwork, terrace units, lift shafts and lifts, cladding, roofing, seating and all other above-ground elements.
The majority of these loads will be transferred into the ground through the stand’s steel columns - the same type of steel columns that you will have seen in the recently constructed infills behind blocks 1 and 9 in the main stand.
The design team will have calculated the loads generated by the superstructure and determined how much of that load is transferred through each individual steel column and into each foundation.
Type of piling
Once the designer has determined the loads passing through each column and understood the ground conditions from the geotechnical investigation (GI), they can design the most appropriate foundation solution – in this case, a piled foundation.
Each column will be supported by a number of piles – you don’t tend to see too many single pile foundations. The calculation will be along the lines of… column load / pile capacity = number of piles beneath that column. Typically, it’ll be 2-4 piles beneath each column.
There are several different piling methods available, but they’re using Continuous Flight Auger (CFA) piling. This approach is particularly well suited to sites like this because it generates significantly less noise and vibration than many alternative piling techniques, helping to minimise disruption during construction.
Piling operations
The large item of plant carrying out the work is the piling rig. Attached to the rig is a long steel auger (like a big drill), which rotates into the ground to the required depth. The diameter of the auger determines the diameter of the pile itself – it looked to be either 450mm or 600mm when they were piling the corners. The auger continues drilling until it reaches the design depth, which could be in the region of 15–20 metres for the corner structures.
Once the required depth has been achieved, the process is reversed. As the auger is slowly withdrawn from the ground, the excavated material is brought back to the surface and removed by a waiting dumper. At the same time, concrete is pumped from a waiting concrete wagon, through the hollow centre of the auger and into the void being created.
When the auger has been completely removed, a steel reinforcement cage is then lowered into the wet concrete and left to cure. It’ll look something like the image below.
The corner stands are quite constrained sites, so I expect they were probably achieving 10-15 piles per day. Whereas the South Stand site is a little more spacious, so I expect they might be able to achieve 15-20 piles per day. They might even be able to get two pile rigs working simultaneously and really accelerate the works.
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Pile caps
As mentioned in a previous post, the piles need to be joined together to perform collectively beneath each column - that’s what the pile cap does. This activity is currently ongoing in the corners.
While the concept is relatively straightforward, the construction process is often quite fiddly and time-consuming. Pile caps can be around a metre deep and require substantial excavation around the completed piles to allow the reinforcement and concrete works to be carried out. On a constrained site, with multiple pile caps being constructed in close proximity, this can create quite a logistical challenge.
The screenshot below is from the south stand foundation layout. This is just a typical 20m x 8m or so section of the stand, but it displays all the key components well. I’ve marked up the following: steel columns in red, piles in yellow, pile caps in blue and ground beams in green. You can see how congested this work is. It also shows 2, 3 and 4 pile configurations well and the shape of their respective pile caps.
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The pile cap will also incorporate the holding-down bolts that the new steel columns will eventually be fixed to. These bolts need to be positioned very accurately, as they determine the exact location of the steel frame above. It’s not uncommon for there to be positioning issues, but it does cause follow on trades an issue which impacts time and money.
Pile caps are often connected to one another via ground beams to ensure they too are working collectively – just to add to the work!
When the pile cap concrete is poured, the contractor will also cast a series of concrete cubes These are tested at specified intervals to confirm when the concrete has achieved its required design strength. Once the necessary strength has been reached, the pile cap can safely support the loads from the steel columns, allowing the erection of the superstructure to begin.
Ground floor slab
A ground floor slab will also likely be constructed to provide the necessary hardstanding and finished floor level for the ground floor of the stand. I'm not sure whether this will be installed as part of the pile cap works, or whether the contractor will wait until the steel frame has been erected and complete the slab at the end.
Stair and lift foundations
The lift shafts in the corner stands will also require their own foundations, following many of the same principles described above. The key difference is that, rather than supporting steel columns, these foundations will support reinforced concrete walls, meaning the detailing will be slightly different.
However, the overall concept remains the same: the loads from the lift shaft are transferred through the foundation and ultimately into the ground via piles. A similar approach is likely to be adopted for the stair cores within the South Stand, which will also require substantial foundations to support the concrete structure above.
So, if you read all that, well done!
The next time you see the piling rig shuffling around site, or an operative fixing a reinforcement cage into a freshly poured pile, you may have a slightly better understanding of what’s going on beneath the surface and the incredible works that the site team are proceeding with at pace.
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