How much top soil should be removed

sea12

Hi just starting my new house and builder appointed. Drive way dig out and general house area dug away and 804 stone out into driveway. The thing is that only 4-6 inches closer to 4 was dug out. When the stone is put in it makes the driveway level with the grass rather than having a nice step up in to grass. Feel I've paid for all topsoil to be removed. Builder says he only ever takes out that amount.
I'm more concerned about putting the slap of concrete for house on 3 inches of top soil underneath it where there is a risk of movement.
He is s reputable builder but one of those that's it's his way and says he always does it this way but I always thought all top soil has to removed and not too comfortable with it.

Any opinions?

Stanford

Was it specified as to how much top soil was to be removed?

If the driveway is level with the grass this is bad practice as the finish can spall over onto the grass

Stanford

Re- read your post again, does your builder propose to lay a foundation slab on topsoil?

sea12

Stanford wrote: »

Re- read your post again, does your builder propose to lay a foundation slab on topsoil?

Sorry should clarify that, he has marked out the ground floor plan with lime and will dig the foundation this week but while the external and internal walls will be dug out and filled with concrete. Then it will be blocked 2-3 blocks and then this is where the slab will be filled.
I know there will be a radon barrier but there will still floor areas where top soil will be. Does this make sense. I'm not great at explaining it.

Rows Grower

You need to consult an engineer with haste.

Victor

Do you have a Safepass to enable you be on site?

What does your engineer say?

Rows Grower

Victor wrote: »

Do you have a Safepass to enable you be on site?

What does your engineer say?

That made me smile Victor.

sea12

Rows Grower wrote: »

That made me smile Victor.

Went with architect as he did the planning, condtruvtion drawings and draw down,

rayjdav

Victor wrote: »

Do you have a Safepass to enable you be on site?

On assumption he is not doing any work, he does not require one under the regs..;)

mickdw

It's simple.
No vegetation should be left behind.
so the builder is going to dig foundation and build up blocks but I assume he is going to them fill the floor from this new stone layer which will be leaving some vegetation behind.
Get your Certifying Engineer to inspect when he starts to dig out out foundation.

Odelay

rayjdav wrote: »

On assumption he is not doing any work, he does not require one under the regs..;)

Correct!

Rows Grower

sea12 wrote: »

Went with architect as he did the planning, condtruvtion drawings and draw down,

Spend a few bob on a structural engineer now and get him to look at the work done already and talk to the builder about what he intends to do re the foundation works.

You only get one chance to do the foundation properly.

Stanford

I take it from the above that there was no Engineer and hence no specification for the builder to follow? As above you will only get one chance to rectify this

Gumbo

Engineer involved?
Who specified 804 hardcore and how close to the foot print of the house does it go to.

Stanford

kceire wrote: »

Engineer involved?
Who specified 804 hardcore and how close to the foot print of the house does it go to.

I don't know, thats why I asked...............

sea12

So if I get an engineer involved which looks like I should how does that work with commencement notice gone in?

Lumen

I know this is a construction question, but top soil is precious stuff which takes thousands of years for nature to make, so aside from it being a crappy support for a house, leaving a few inches under a slab is a waste of good material, better to use it in landscaping where you will be able to grow amazing things with greater depth.

Stanford

sea12 wrote: »

So if I get an engineer involved which looks like I should how does that work with commencement notice gone in?

Strictly speaking Commencement Notices should be submitted not less than 14 days and no more than 28 days before the commencement of works, however thats not your problem now, get immediate professional advice because you risk damp and subsidence if the foundation base is incorrectly supported, have you taken up copies of the Builder's insurances?

sea12

Stanford wrote: »

Strictly speaking Commencement Notices should be submitted not less than 14 days and no more than 28 days before the commencement of works, however thats not your problem now, get immediate professional advice because you risk damp and subsidence if the foundation base is incorrectly supported, have you taken up copies of the Builder's insurances?

I have requested them as I need to send into bank as part of mortgage. Was meant to get them tomorrow anyway.

Stanford

"Went with architect as he did the planning, condtruvtion drawings and draw down"

Did the architect specify foundation details for the builder?

Wildly Boaring

All above have given the engineer advice, ditto, you need one now!

Out of interest, did he just take out 4 inches of topsoil and put in 4 inches of 804 and say "I always do that?

The finished level on the stone would not overly bother me. Can be sorted with kerbing and landscaping usually.

That make up would definitely bother me. It will not survive.

Mentioned above too but normal 804 cannot be next to the building as it is not tested for pyrite. You're probably fine as majority of quarries don't actually produce 804 anymore just stone to SR 21 annex E.

This is all stuff for the engineer before you even get to the foundations.

Stanford

Was the Architect present when the setting out was done? Who will approve the foundation layout this week?

You need to be talking to an Engineer tomorrow, perhaps the Architect can recommend somebody urgently

sea12

Stanford wrote: »

Was the Architect present when the setting out was done? Who will approve the foundation layout this week?

You need to be talking to an Engineer tomorrow, perhaps the Architect can recommend somebody urgently

No architect wasn't on site for layout. It was he who recommended builder to me. I did tender and went to view some of his previous houses and met with owners who seemed happy enough.

804 was for the driveway where he took off 4 inch of top soil and filled in with 804. Just mentioned that he had to get it from one supplier as needed to get Certs for it.

Yes construction drawings done for foundations. Just looked at it and says clear all top soil.

Ok will ring architect first thing in morning and speak to him but also get an engineer as perhaps they are too close.

Stanford

""clear all top soil"" is hardly a foundation specification, find an independant engineer asap, sounds like a cosy club

sea12

Stanford wrote: »

""clear all top soil"" is hardly a foundation specification, find an independant engineer asap, sounds like a cosy club

Ah no it has full detailed spec drawing done for foundation I was just replying to an earlier post asking was it specified..

Gumbo

sea12 wrote: »

Ah no it has full detailed spec drawing done for foundation I was just replying to an earlier post asking was it specified..

Ground condition survey carried out?
Sub floor fill material and grade of stone ranging from T1 to T4, which are structural items and should be designed by an engineer.

804 doesn’t cut it anymore, especially if the driveway continues tight up to the house. SR21 means that the fill material to within 1m of the dwelling now has to be SR21/IS888 compliant (Annex E).

Who is designing the structural elements?

Oneplus

Hi all few questions relating to my new build. Can someone please explain preparing a site for a new build to me on a green field site with soil of typical bearing capacity.

1) Typically how much top soil is removed to bring down to subsoil level where there is no organic matter? I couldnt get a definite answer on this but read its typically 300mm?

2) Once the top soil is removed, foundations are to be marked with lime/spray. Is this line the Internal or external wall measurements?

3) Footprint marked, Foundations are dug. But to what depth. I read the top of the foundation should be a minimum of 600mm below subsoil to avoid frost heave. Is this 600mm at subsoil or outside ground finish level?

4) The soil inside the area of the internal footprint, should this be reduced to accommodate the hardcore fill or is this the level at which the fill will be placed upon. ie. rising walls from

I read earlier in this thread an engineer should specify this. What soil tests does he carry out in order to determine depths.

Thanks in advance

BryanF

1. Depends on site conditions. But yes 300 is possible.
2. Neither. Footprint of foundation. Structural design required.
3. Neither. Structural design required
4. Structural design required.
5. Depends. Engineer will advise based on site conditions

Wildly Boaring

Oneplus wrote: »

Hi all few questions relating to my new build. Can someone please explain preparing a site for a new build to me on a green field site with soil of typical bearing capacity.

1) Typically how much top soil is removed to bring down to subsoil level where there is no organic matter? I couldnt get a definite answer on this but read its typically 300mm?

2) Once the top soil is removed, foundations are to be marked with lime/spray. Is this line the Internal or external wall measurements?

3) Footprint marked, Foundations are dug. But to what depth. I read the top of the foundation should be a minimum of 600mm below subsoil to avoid frost heave. Is this 600mm at subsoil or outside ground finish level?

4) The soil inside the area of the internal footprint, should this be reduced to accommodate the hardcore fill or is this the level at which the fill will be placed upon. ie. rising walls from

I read earlier in this thread an engineer should specify this. What soil tests does he carry out in order to determine depths.

Thanks in advance

Engage an engineer.

Very broadly
1. All the topsoil. Not being smart. I've seen land with zero topsoil and land with 500mm. Typical good grassland about 350 to 400.
Worrying question. Topsoil and subsoil are not te same

2. Either. Usually mark centre of found myself. And profiles or spinning laser for level. Make sure to set a benchmark in concrete day 1

3. Depth is deffo engineers job. Last site 300mm deep found and 3 courses deadwork. But he had possibly needed more deadwork than usual??

4. Fill back up off good substrate. Fill must be SR21 annex E!!

Soil tests. Not 100% on private house.

These are broad answers. You NEED an engineer