Piled foundation cost

[Bonner]

After saying never again, we are looking at another self build ‘opportunity’! The plot is ideal in terms of size and location but the compromise is soft clay requiring piled foundations. A full ground investigation has been done by the vendor which concludes that piling is definitely required. I know it is a piece of string question but can anyone suggest a reasonable cost difference between strip founds and ‘standard’ piles + ring beam? Looking at 220m2 two storey house with simple form factor so 110m2 rectangular footprint, timber frame and brick skin. TIA

[MPx]

No recent knowledge so unlikely to help, but FWIW:  In 2012 we had a pile and ring beam foundation done due to unstable ground.  Not a regular shape (you need support for any internal load bearing), but approx 55 linear meters using 44x 9m piles with a ring beam and a few pins cost £27,480.75.  But how much for strip foundations in 2012 to compare - no idea???

[Bonner]

Thanks. I know I will need to talk to a piling contractor in due course. Just trying to get a feel of the cost risk for valuation purposes. From fairly recent experience I can estimate the cost from ground up, just go no idea if I need to add £10k, £30k, £100k for piling.

[Mr Punter]

I would think £35k extra would do it assume 300mm piles up to 6m.  £20k piling £15k ground beams.  You could get indicative quotes based on your ground investigation.

[Bonner]

On 30/08/2026 at 19:05, Mr Punter said:

I would think £35k extra would do it assume 300mm piles up to 6m.  £20k piling £15k ground beams.  You could get indicative quotes based on your ground investigation.

Thanks, I would be able to live with that sort of cost. If it comes to much more the project is not viable for me. Will get in touch with a few contractors.

[mjc55]

But you are not going to get a fixed price for piles I suspect!  Until they start inserting piles they wont really know depths so any quote would be an estimate I suspect.

[Mr Punter]

5 minutes ago, mjc55 said:

But you are not going to get a fixed price for piles I suspect!  Until they start inserting piles they wont really know depths so any quote would be an estimate I suspect.

 

If the ground investigation is decent they should be able to get a good idea.  Also access and proximity to adjacent structures can have an impact that the piling contractor can factor in.

[Nickfromwales]

13 hours ago, Mr Punter said:

 

If the ground investigation is decent they should be able to get a good idea.  Also access and proximity to adjacent structures can have an impact that the piling contractor can factor in.

You can ask for this to be more 'in depth', so they charge more for the investigations and remove as much ambiguity as is practicable.

[saveasteading]

On 30/08/2026 at 08:21, Bonner said:

piling is definitely required. 

Do you have access to the borehole logs?

Just a statement that piling is required is of little use.

Is there hard ground at 5m depth or 50m? How soft is the clay? 

Does only the structure require support but not intermediate floor areas?.

 

That said, a starting point of "about 30 or 40k" lets you start on feasibility.

 

But there are lots of piling techniques too. By considering that and the method of construction you could be saying "allow 20k to 80k".

 

I've probably done about 20 piled buildings and often used a different method to that suggested in initial reports. But never for clay... yours must be very soft indeed.

 

Any chance of seeing a borehole record?

 

And what about the house? Big/small/ conventional or huge rooms, 1 or 2 storey?

 

[Gus Potter]

On 30/08/2026 at 08:21, Bonner said:

fter saying never again, we are looking at another self build ‘opportunity’! The plot is ideal in terms of size and location but the compromise is soft clay requiring piled foundations. A full ground investigation has been done by the vendor which concludes that piling is definitely required. I know it is a piece of string question but can anyone suggest a reasonable cost difference between strip founds and ‘standard’ piles + ring beam? Looking at 220m2 two storey house with simple form factor so 110m2 rectangular footprint, timber frame and brick skin. TIA

Now by now you should know that there is no way any of us that can take a punt on this. 

 

Post your geotech info, a site plan etc. You know the rules, the more info you provide the better quality response you'll get. 

[Nickfromwales]

6 hours ago, Gus Potter said:

there is no way any of us that can take a punt on this. 

Indeed, and, as above, even a quote given to you will be loaded with caveats; stating that they’ll need to keep sending the pile down until it hits something robust etc.

 

You need a creative / proactive SE who could consider all options and value engineer (and not over egg it!). 

[Bonner]

Thanks, appreciate all the comments. I will post more detail later.

[saveasteading]

I generally used a piling company that had several technical options ( driven, auger, vibro) ( end bearing, surface friction, ground inprovement) so that they could help decide on the best solution. But this involves 2 way trust which takes time to form.

And they aren't likely to suggest another method of construction with no piling.

Looking forward to your info.

[Alan Ambrose]

We had an estimation module in engineering school that asked us to do critical calcs in our head and come out with approximate answers. This allowed a very valuable sanity check on the fancier version of the calcs using accurate numbers. If the results differed by more than, say +- 50% you had a big problem.

 

So, saying that, I just had some augur piling done. There's generally a fixed cost for design / mobilisation (i.e. getting off our arses) / testing etc and a variable cost per pile or metre, but sometimes the sales person might trade one against the other for window dressing. I was quoted £1.29K per pile / £92 per metre for 350mm diameter 14m piles and only a couple of £K for design etc. I was also responsible for the muckaway.

 

Let me guess that you'll have 20 off 8m piles (who knows without seeing your soil investigation or knowing how heavy your house is going to be). That's £15K plus some fixed costs and the muckaway, say £20K. I'll guess that the ring beam will cost about the same as simple strip founds. So plus £20K for pile support. Sure, maybe you'll need 12m piles or longer and the cost will scale roughly linearly - nobody knows because you have not provided any info besides 'soft clay'.

 

I bet a couple of local piling companies will be interested enough to give you a ballpark. To get an accurate quote number you need:

1. A soil investigation with load bearing numbers and a sense of groundwater height.
2. SE calcs of your house loads and a rough slab/founds design.
3. The piling co will then do a pile design with a 3x safety factor and give you a reasonably firm quote. On consistent soft clay you shouldn't find anything too unexpected unless you suspect mine workings, archaeology, underground lake etc. A local BCO might give you an opinion on that too.

This is what the interesting page(s) of the SI look(s) like. The N=xx result is what you're after and gives you an indication of the load bearing capacity.

 

 

The SI may even give you a feel for what reasonable piling might look like, but the piling company will want to refine that calc.

 

Edited 4 hours ago by Alan Ambrose

[Bonner]

Well here goes, a few extracts from the report. Note it does not say piles are absolutely necessary, only recommended due to trench depth, stability and potential heave. Once again, appreciate any suggestions.