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Do you actually need a soil survey?


SuperJohnG

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I'm trying to get prices for a Soil survey in Ayrshire, Scotland.

 

Prices currently ranging from 1000-1500 plus VAT. 

 

The only thing I think I want from the survey is for someone to tell me the load bearing capacity....I don't need percolation tests as I don't have any soakaways and the land isn't contaminated.

 

I completely begrudge the money as really it's looking in the hole and saying what it looks like, which is no more than an an hour or two on site likely looking at test pits and likely they will take no liability on.   

 

I just need the right info to pass to Hilliard Tanner as he will do the foundation design for me (Insualted passive slab). so do you actually need it? will BC ask for it?  

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We did it when the electric connection was being done. Engineer arrived on the same day and got the digger driver to dig a couple extra holes down to our foundation depth. She then just did a visual check and grab a handful of the soil.. was fairly obviously just standard red boulder clay and didn't warrant any further investigations. Think the whole exercise was a couple hundred quid.

 

A lot depends on the local geology and history. If there is a reason to suspect something out of the ordinary, a detailed investigation may be needed.

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You SER engineer will need site survey information in order to sign off the certificate and Building Standards will ask for a copy of the SI

A lot comes down to the site history/location etc and a bit comes down to your attitude to risk... normally you could get a stage 1 SI done which would tell you if there's more investigation required but that's still money spent! 

What you need for the engineer is trial pits, i.e. you dig a big hole and they look down the hole and nod or shake their heads ? - Just ask the engineer what SI they'll need to be able to complete the design and what the local authority usually accept (some Building Standards offices seem to want to see a lot more where there's any slight hint of a possibility of contamination or ground gas etc...

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I had one done for exactly the reason you mentioned, so that the bearing capacity of the soil is known.

 

As it stands I hit sandstone at approx 800mm down but there was a pocket of 'made ground' which one of the boreholes hit.  Subsequently the recommendation was then made that the whole site was stripped down to 1.5m and then built back up again to the required depth. Very expensive.

 

After discussion with the soil dude and BC it was agreed that I could stop at sandstone and only dig down any soft spots.

 

It seems that the soft spots were where rubbish had been buried back in the day when bin men didn't exist. Found all sorts of glass bottles and broken crockery in there.

 

Was a pita but luckily most of it was solid sandstone at 800mm depth.

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Like most on here we were required by planning to have a soil survey SE came down and said your across from a sand pit so i know it will be clay and sand 

So no need 

We are hoping to do the same on our next build 

 

The plot had had a contaminated land survey three years previous and had been laid to lawn ever since 

We still had to spend £450 on an up to  date C L survey 

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8 minutes ago, SuperJohnG said:

Thats definitely helpful. Thanks @A_L

Helps me define the conditions.  

 

You can't really use the small buildings guidance any more tbh, you'll need an SER cert to accompany your warrant application and its only the se who can tell you what si is required - the original question about soil testing isn't addressed in the small buildings guidance...

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30 minutes ago, the_r_sole said:

 

You can't really use the small buildings guidance any more tbh, you'll need an SER cert to accompany your warrant application and its only the se who can tell you what si is required - the original question about soil testing isn't addressed in the small buildings guidance...

But it gives me an idea of what soli beating pressures are whichnis really what I want to know. 

 

Ultimately if I have to give someone 1k I want to knkw what they are undertaking and how technical it is to warrant the money. Sticking your thumb in some mud shouldn't need someone to charge 2k. 

 

In reality ill get the SI done to get an input for tanners to design the foundation system. Then as you say the SER SE will include it. 

I should maybe xheck what they require as its a different engineer (likely the one doing the superstructure)

 

It's, as many things I have found in the housebuilding, a very wooly process where there is no defined rules. Which ours me somehwat out my comfort zone, I'm a Chartered Mech engineer and driven by process and value add. So if there is a need for soemthing I like to know its justified and why it is required. 

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It doesn't matter if you have an idea tbh, it matters what the SER certifier needs! It's a pretty prescriptive process in Scotland - all you can do is supply the information that the certifier needs to provide the paperwork to tick the right boxes.

Ask the SER engineer exactly what they require (rather than what they would ideally have! )

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7 hours ago, SuperJohnG said:

I'm trying to get prices for a Soil survey in Ayrshire, Scotland.

 

Prices currently ranging from 1000-1500 plus VAT. 

 

 

Is that with you or them providing the digger?

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