What Usually Decides the Cost and Timeline
When homeowners in London plan an extension, most of the attention goes into layouts, finishes and planning permission.
Foundations are often treated as a technical detail that will “sort itself out later”.
In reality, piling decisions made early (or late) often determine whether a project runs smoothly or turns into a series of delays.
At KHB Piling LTD, we are usually brought in when something unexpected appears on site.
This article explains what actually influences piling choices for extensions in London — based on what we see day to day.
Why extensions trigger piling requirements in London
London ground conditions change quickly and rarely follow neat assumptions.
Even streets with identical houses can sit on very different soil layers.
That’s why building control often requires piling for extensions, especially where:
- existing foundations are shallow or undocumented
- the extension adds load close to neighbouring properties
- the site sits on variable or made ground
- tree influence affects clay movement
This is particularly common on projects we see under mini piling foundations, where access and proximity to boundaries matter just as much as ground strength.
The point most projects underestimate: access
Access is often the real constraint — not soil.
Side alleys, garden steps, fences and neighbouring extensions all affect what piling method is realistic.
For many London homes, piling in London means working with compact rigs, staged deliveries and tight working windows.
If this isn’t considered early, costs rise fast.
Mini piling vs deeper solutions – how the choice is made
Mini piling is often the right answer for residential extensions, but not automatically.
We look at:
- structural loads from the engineer
- available headroom and working space
- distance to neighbouring foundations
- soil consistency across the footprint
In some areas, especially where clay is consistent, CFA piling can be quicker and cleaner.
On mixed ground or higher loads, rotary bored piling may be unavoidable.
What building control actually checks
Building control doesn’t just look for piles in the ground.
They want to see that the method fits the site conditions and the structure.
That includes:
- pile depth and diameter
- reinforcement and concrete specification
- connection to ground beams
- consistency with approved drawings
This is where experienced coordination matters.
On extension projects linked with groundworks or basement construction, piling errors tend to multiply later stages.
How long piling for an extension really takes
Most residential piling works are far quicker than people expect.
A typical mini piling job for an extension often looks like:
- setup and access preparation: half a day
- pile installation: one working day
- concrete trimming and inspection: same or following day
Compared with mass excavation and deep concrete pours, piling is often the faster route — with far less disruption to neighbours.
Cost isn’t just about piles
When homeowners ask about piling cost, they usually focus on a price per pile.
In practice, total cost depends more on:
- access constraints
- rig mobilisation
- number of working visits
- coordination with other trades
This is why early consultation with a specialist piling contractor in London almost always saves money overall.
When to speak to a piling contractor
The best time is before construction starts — ideally once drawings exist but budgets are still flexible.
A short site visit can confirm whether piling is required and which method makes sense.
If you’re planning an extension anywhere across London, including areas listed in our locations we serve, early advice avoids expensive changes later.
Extensions start below ground
Foundations rarely get attention once they’re covered — but they determine everything above.
At KHB Piling LTD, our aim is simple: install the right foundation once, sign it off properly, and let the rest of the build move forward without issues.
If you want to talk through your plans or check whether piling is required, you can contact our team here for a straightforward, no-obligation discussion.
My name is Kamil, and I specialise in piling services in London. I am dedicated to advancing KHB Piling LTD, a trusted contractor delivering high-quality foundation solutions for both residential and commercial projects. With the expertise and commitment of our team, we provide reliable piling services, including mini piling and CFA piling, tailored to meet the unique requirements of each client.
