Soil Investigation - £4K+ is high?

[Dreadnaught]

I might add that my foundation build-up will be as follows.

 

Bottom to top:

1. Blinding
2. Heave protection, 220 mm, such as "Heave Stopper" or "Jablite" or "Cellcore". The thickness of the layer is dependent on the physical characteristics of the clays.
3. PIR insulation, 200mm (100 mm for the edge thickening ("ring beam") and ribs). Also to contain various water supply pipes.
4. Reinforced concrete. 100 mm (200 mm for the edge thickening ("ring beam") and ribs). Also to contain under-floor heating pipes.

Quite a thick set of foundations. 

 

The insulation is usually EPS but I was able to choose PIR to make the build-up thinner because the insulation is not load bearing. As I have learnt, PIR would probably support the weight just fine but it has not be characterised sufficiently well that an engineer would be willing to specify it if it were load bearing (or, more to the point, his liability insurance would be willing to insure it). PIR can be only used when not load bearing, at least at present.

Edited May 17, 2020 by Dreadnaught

[Declan52]

For more information on how the vibrating stone type piles work then @AnonymousBosch is your point of contact. There is plenty of reading in his blog.

 

[Hilldes]

3 hours ago, Dreadnaught said:

I might add that my foundation build-up will be as follows.

 

Bottom to top:

1. Blinding
2. Heave protection, 220 mm, such as "Heave Stopper" or "Jablite" or "Cellcore". The thickness of the layer is dependent on the physical characteristics of the clays.
3. PIR insulation, 200mm (100 mm for the edge thickening ("ring beam") and ribs). Also to contain various water supply pipes.
4. Reinforced concrete. 100 mm (200 mm for the edge thickening ("ring beam") and ribs). Also to contain under-floor heating pipes.

 

Thanks @Dreadnaught. So it looks like a ground bearing slab. The piles support what  - not a conventional reinforced concrete ring beam?

 

Do you have any examples of completed projects please?

[PeterW]

4 minutes ago, Hilldes said:

Do you have any examples of completed projects please?

Start with @AnonymousBosch as his is this design from memory. 

[Dreadnaught]

15 hours ago, Hilldes said:

The piles support what  - not a conventional reinforced concrete ring beam?

 

The piles support the entire insulated raft, across the full floor area of the dwelling. There is no separate ring beam. The raft has the edges thickened, which act like a ring-beam in terms of supporting the exterior walls. And because the majority of the raft will be quite thin by the standards of concrete foundations (just 100mm for most of the raft) there will also be reinforcing cross thickening to form structural ribs in key areas.

 

I have also specified in my build that none of the internal walls be structural, which is quite easy to do as mine is a bungalow, and gives great flexibility.

[ToughButterCup]

To answer your first question directly - the price depends on trial depth, number of cores and level of detail in the feedback.

 

You cannot do without a proper soil survey.  Unless your risk appetite is very high.  In which case any reputable piling company will want to do their own survey or insist you get one done.

 

Is 4k (your quote)  expensive?  Get 2 more done.  And when you get the numbers back,  be sure to compare like with like.

 

Not always easy

 

[Hilldes]

2 hours ago, AnonymousBosch said:

To answer your first question directly - the price depends on trial depth, number of cores and level of detail in the feedback.

 

You cannot do without a proper soil survey.  Unless your risk appetite is very high.  In which case any reputable piling company will want to do their own survey or insist you get one done.

 

Is 4k (your quote)  expensive?  Get 2 more done.  And when you get the numbers back,  be sure to compare like with like.

 

Not always easy

 

 

Thanks, @AnonymousBosch got multiple quotes, going with the one at £2K inc VAT which includes the lab analysis.

[Hilldes]

3 hours ago, Dreadnaught said:

 

The piles support the entire insulated raft, across the full floor area of the dwelling. There is no separate ring beam. The raft has the edges thickened, which act like a ring-beam in terms of supporting the exterior walls. And because the majority of the raft will be quite thin by the standards of concrete foundations (just 100mm for most of the raft) there will also be reinforcing cross thickening to form structural ribs in key areas.

 

I have also specified in my build that none of the internal walls be structural, which is quite easy to do as mine is a bungalow, and gives great flexibility.

 

Thanks @Dreadnaught. Would be great to see a diagram when your design is complete. I'll see if my SE could design such a thing (I would guess not).

[Thorfun]

I just got a quote back for our geotechnical survey. the company are offering this for the fieldwork:

 

Dynamic Sampling: One days work on site, to provisionally include 2no boreholes to 3.00m and 2no to 5.00m (the depth and number of holes will depend on drilling conditions, site constraints etc).

Dynamic Probing: SHDP type 2 probing in conjunction with the dynamic sampling.
Monitoring wells: We have allowed for installing 1no monitoring wells to a provisional depth of 5.00m

Geotechnical field tests: in-situ testing to include: CBR testing using a TRL DCP

 

it also includes desktop study, groundwater monitoring and laboratory testing. total cost is £3k inc. vat

 

I thought it was reasonable and as we're having a basement a most definite requirement! They even say that they'll report specifically on the basement we're after as well as many other things.

 

The second quote I got seems a little more comprehensive including a data logger to measure groundwater levels at 15 minutes intervals over a period of 3 weeks. they came in at £3200 inc. vat.

 

I'll be getting a couple of more quotes as well to compare but it seems that it'll cost me around £3k to get this done.

[Hilldes]

The one I went with @£2k sounds similar to your first option. Will post the work that was actually done when I get the report.