Large conifer stump on/near footings area

[SteamyTea]

6 hours ago, Gus Potter said:

If it was me and things looked promising I would have a look at something along the lines of the very rough sketch below and start to tweak the design to get it just right

Not trying to be clever or anything, just make sure I was not totally off track when I suggested this.

On 02/05/2023 at 12:09, SteamyTea said:

If you bridge over the ground stump/root combo with a bit of rebarred concrete, that would support most things.

I did not add any detail as I am basically a lazy bastard, and there are others that are much better at calculating this.

[Deejay_2]

On 13/05/2023 at 01:09, Gus Potter said:

No an SE is not "duty bound". A lot of the NHBC information is for guidance. If you can show that the site conditions require a different approach and you can as an SE justify that then no problem.

 

I made a long post before about the things you need to consider. If it was me and things looked promising I would have a look at something along the lines of the very rough sketch below and start to tweak the design to get it just right. I have not shown the top bars on the plan view.

 

 

 

Key ponts are:

 

1/ The concrete is all cast in the one pour with the same mix of concrete. You pour the deeper trench fill bit under the blue line which is bit of DPM plastic. Smooth that off, go and pour concrete around the rest of the found.

2/ At the same time drop in the A142 mesh over the stump area and the M16 bars.

3/ Finish pouring the found over the stump area dropping in the top bars when you go. By that time the trench fill bit will have taken up a bit.

4/ The DPM decouples to some extent the reinforced part of the found from the deeper "trench fill" looking bit below. This means you don't have to follow for example the rules for steps in founds and if the deeper thicker concrete shrinks more than the rest of the found the shrinkage stress is less likely to be transferred to the strip or vs versa.

5/ Make the bar length so you can cut them from stock lenghts. Here the bar length are base on a stock length of 6.0 m

6/ The short 1.3m top bars are there in case the trench fill bit works too well and creates a hard spot that would cause the found to crack where the trench fill comes up to meet the rest of the strip found.

7/ The found is widened locally a bit just to reduce the bearing stress on the ground below.

 

 

 

Hi and thank you.  Does all this apply if the soil is not clay.  We have good soil and the trial pits dug at 1.2 m have no water in them even though it poured most of last week.  Also no caving in of either pit.  The BCO has said the fill should be 1.2 m deep throughout with him assuming the tree stump is removed or ground down.   

 

The diggerman is coming on Thursday to refill the trial holes and dig one trench (south elevation whereas stump is north elevation).  BCO will inspect the trench and we should receive a commencement notice, which is what we are seeking (before 15 June 23).  

 

Following the trench dig, the diggerman will try and remove the stump by digging around it which will encroach upon the proposed northern elevation foundation area.  If he is unable to remove the stump he will ask a grinder to grind it down (he will be able to go deeper as a result of the work done by the diggerman). 

 

Because we are not digging the northern elevation trench at this time I am trying, from your drawing, to establish whether what we intend doing will marry up with your suggestion ie dig around stump and either nudge or pull out (unlikely I know) and if unsuccessful employ a specialist grinder to grind it down as much as possible.  The area will have time to settle as we are not undertaking further work at this time.

 

The drawings are really useful and we shall refer to them in the future but I would like to be sure the work undertaken this week in removing the stump will not prevent us following your plan at a later date.

 

Many thanks and I have my camera ready.

 

 

[saveasteading]

21 minutes ago, Deejay_2 said:

all this apply if the soil is not clay.  We have good soil 

What is the ground? Don't need to be technical , just as you see it.

[Deejay_2]

8 minutes ago, saveasteading said:

What is the ground? Don't need to be technical , just as you see it.

I would say dry sandy coloured with stones in it.  Would a photo help, bearing in mind I only seem able to add one photo!!!

[saveasteading]

Photo would be good. Also, if safe in the hole, do some simple tests.

Push your thumb into the side of the hole. What effect is there?

Take a broom or rake and push the handle down into the base. How far does it go?

Take a lump from the bottom. How easily does it fall apart in your hands, and what do you see? 

Photos of anything of note.

[SteamyTea]

13 minutes ago, Deejay_2 said:

bearing in mind I only seem able to add one photo

See that paperclip and Add Files.

Click on the Add Files and select the ones you want.

 

[Deejay_2]

Here goes - I think my files are too big and I don't know how to reduce them.

 

Yep, it's saying I'm exceeding something or other.  I'll do another post.

[Deejay_2]

Second photo.  (I will poke the bottom of the trench with a pole and get back to you)

[SteamyTea]

54 minutes ago, Deejay_2 said:

I think my files are too big

If you are using a phone, there are applications that will reduce them.

I use PhotoCompress (Android)

It is probably built into a iPhone as there is nothing on Earth they cannot do, apparantly. 

Edited May 14, 2023 by SteamyTea

[Deejay_2]

39 minutes ago, SteamyTea said:

If you are using a phone, there are applications that will reduce them.

I use PhotoCompress (Android)

It is probably built into a iPhone as there is nothing on Earth they cannot do, apparantly. 

I don't have a mobile phone so using camera.  I don't upload many photos so can usually manage.  

The stuff that has been removed - the sandy coloured part - is crumbly between my fingers, but not fine, and is full of bits of stone.  I was unable to push a pole into the bottom as I didn't feel safe.    I can't see any clay but I am no expert.  

Do the pictures help - I've uploaded another one.

 

 

 

 

 

[saveasteading]

OK that looks good. I'd say it was clayey with stone. But it looks really strong, with those teeth marks in the bottom.

The vertical sides are a good sign too.

[SteamyTea]

30 minutes ago, Deejay_2 said:

don't have a mobile phone so using camera

Then Irfanview Portable.

 

[Deejay_2]

4 hours ago, Deejay_2 said:

Hi and thank you.  Does all this apply if the soil is not clay.  We have good soil and the trial pits dug at 1.2 m have no water in them even though it poured most of last week.  Also no caving in of either pit.  The BCO has said the fill should be 1.2 m deep throughout with him assuming the tree stump is removed or ground down.   

 

The diggerman is coming on Thursday to refill the trial holes and dig one trench (south elevation whereas stump is north elevation).  BCO will inspect the trench and we should receive a commencement notice, which is what we are seeking (before 15 June 23).  

 

Following the trench dig, the diggerman will try and remove the stump by digging around it which will encroach upon the proposed northern elevation foundation area.  If he is unable to remove the stump he will ask a grinder to grind it down (he will be able to go deeper as a result of the work done by the diggerman). 

 

Because we are not digging the northern elevation trench at this time I am trying, from your drawing, to establish whether what we intend doing will marry up with your suggestion ie dig around stump and either nudge or pull out (unlikely I know) and if unsuccessful employ a specialist grinder to grind it down as much as possible.  The area will have time to settle as we are not undertaking further work at this time.

 

The drawings are really useful and we shall refer to them in the future but I would like to be sure the work undertaken this week in removing the stump will not prevent us following your plan at a later date.

 

Many thanks and I have my camera ready.

 

 

Thank you.  So having uploaded the photos is the general concensus that what we are going to do on Thursday (as post above) is OK and we won't be making problems for ourselves when we return at sometime in the nearish future to recommence work.

[saveasteading]

Yes. You might have to dig out a bit more where big roots come through the trench. Roots can grow and shrink and rot. But this is a few shovel fulls if at all.

[Gus Potter]

On 13/05/2023 at 08:06, SteamyTea said:

Not trying to be clever or anything, just make sure I was not totally off track when I suggested this.

No you were bang on @SteamyTea and yes it was your idea first, so not taking any credit for your concept.

[Gus Potter]

On 07/05/2023 at 06:39, The Reverend said:

I have excavated a slightly larger tree for a friend and they leave a massive hole that will need to be back filled and compacted so I would not recommend this. If it were me I would be looking at getting in a reputable tree surgeon and grinding out only what you need to get a lintel or ground beam over it.

Perfect and pragmatic approach for the Reverend.

 

Sometimes blindly following NHBC guidance or an inexperienced BC officer's view can do more harm than good.

 

@saveasteading yes that looks like good ground. Well defined layer between the upper nutrient rich and the structural soil below. If you have a big tap root it may go straight down so if it rots (could take 50 - 100 years as no oxygen) then it probably won't have any effect as the soil will act as an arch at those depths. A way of explaining this.. say you have a 2 foot diameter tunnel 50 feet under the ground.. the ground will span over that and at say 4- 5 feet down from the surface you may not see any noticable effect. A 5" tap root going straight down will have even less effect.

 

Also remember that you can only work from one side due to the boundary wall. You don't want to destabalise the wall. Also if you excavate a massive hole on your side then it will extend well into your underbuilding. What kind of floor are you going to use? Ground bearing slab or suspended floor?

 

The first approach here as the Rev and Steamy et al advocate (the bridging concept was not my idea, the drawing was just to translate that into how you may go about detailing something like that) is to assume you won't get all the roots out and that over time you may get some movement and design for that. I would try this first as it is less intrusive and cuases less soil disturbance.

 

I take it this extension is single storey, not two or three and that you don't have transfer beams landing over the tree stump zone?

 

Once you start to investigate then that drawing I did may be quite conservative.

 

 

 

 

 

 

 

 

 

 

[SteamyTea]

41 minutes ago, Gus Potter said:

No you were bang on @SteamyTea and yes it was your idea first, so not taking any credit for your concept.

I was not looking for fame, just like to know I am still in touch with reality.

 

10 minutes ago, Gus Potter said:

If you have a big tap root it may go straight down so if it rots (could take 50 - 100 years as no oxygen) then it probably won't have any effect as the soil will act as an arch at those depths

Getting there in into taphonomy after that.

[Gus Potter]

57 minutes ago, SteamyTea said:

Getting there in into taphonomy after that.

Not heard of that term before, ta. Every day is a school day.

[Deejay_2]

Diggerman arrived at 8.15 am.

 

8.15 Diggerman arrived. I checked with him what he was going to do and explained that I was concerned about whether the rear elevation measurement on the drawing matched the space available.

 

I have had large laminated plans done so that they had something clear to refer to.

 

9.30 (After tea and biscuits) they had drawn the southern elevation and I went to check. The measurement across was approx 13 m and we needed 14 to accommodate 12 m elevation with 1 m each side. What they had marked out (and I’m sure would not have consulted me about before starting to dig) was totally off the mark The plot is not square and to do it the way they intended would have made it very difficult for a car approaching the garage doors to drive in without having to negotiate.

 

The diggerman boss kept referring to me being a “whittler” and fusspot. I said surely it’s better to agree on the building’s position before the excavation starts. This is what I mean about the way men in these sorts of trades still regard. It gave me a headache having to stand my ground so firmly.

 

10 am and not started digging. The BCO has just turned up and not pleased as the trench has not been dug. When I arranged the visit with their office I said I would phone the BCO when the trench was ready to be inspected but the person who did the booking failed to make a note of this so I am in the bad books again. He said he’d rebook it for tomorrow. So all my careful plans to get everything done today as regards trench and BCO have now gone awry.

 

10.30 diggerman boss went to another job and his employee excavated the newly placed trench. Good soil but a lot of holly roots see pic. He also dug around the tree stump which is enormous with some massive roots. He is unable to take it out so will need to be ground out and the stump buster man is coming this pm to advise on next move, which I will report.  The photo doesn't show how enormous the tap root is and which runs right across the proposed foundation.  

[Deejay_2]

New trench showing Holly tree roots.

[saveasteading]

Anyway the hole is dug. Prune all the roots off tight to the face so they are not in the concrete.  Even the tiniest ones. If the bco says to also wrap the sides in polythene, then agree.

[Deejay_2]

OK - the stump man has been out - he has asked that we dig about a 6 ft square 10" deep area  in front of the stump to form a sort of ramp for him to get his machine in.  If we do this he will be able to get most of the stump out I think.  He is busy for a few weeks so it won't be immediate - £180 which I think is reasonable. 

 

We have a different BCO coming out tomorrow to inspect the trench - I'm going to suggest we at least partially backfill the newly dug trench as it is quite near the wall and if it remains just a trench for example say 18 months it might weaken the wall's structure.  If he says that's OK, we'll probably backfill completely to be on the safe side.  The other BCO said we can't backfill as it would mean we had not commenced work.  We are not doing any concreting at this time.  The tree stump situation is interesting so I'll post as things progress.  Next thing BCO.

[saveasteading]

Photographs and more photographs of the trench, in detail and in context. Not for here  but to prove it was started.

[Deejay_2]

The different BCO called today.  He said the trench is fine.  I asked about part back filling the trench but he said no as that would mean we had not "commenced" the work, which I know is right.  I am just concerned about the nearness of the wall to an open trench.

 

I am now in a quandry as to what to do.  He said get the concrete in but we wanted this to be as least expensive as possible in case I die in the near future and the proposal is abandoned and also due to our current financial situation (plus not 100% certain of diggerman's setting abilities - will get a professional to set out the whole site before any further excavation is done).

 

So 

1. Should we purchase some OSB boards and cover the trench, plus cover the OSB with heavy duty plastic sheeting, leaving the soil dug out piled up at the side of the trench.
2. Wait to receive the commencement email and then wait a further couple of weeks before asking the diggerman to come back and refill the trench.  I'm not dishonest by nature and if they found out and retracted the commencement proof, we'd have to dig it all out again and be back where we are now.  Is there any reason they would find out.  No one else can see the trench.  I would hope the diggerman wouldn't blab but he is a bit of a gossip.
3. Put in the concrete which we really don't want to do.

Any opinions on what individuals would do in my situation would be much appreciated.  

 

[ProDave]

If you want to keep the trenches open for a while I would get some cheap but thick shuttering ply, cut it in strips to match the trench depth, line both sides of the trench with it and then lots of timbers side to side cut to be a tight fit, to brace it and keep the sides under pressure.

 

But surely all you want is a bit of paper from BC to say you have "started the development"  So ask them for that.  If you get that then does it matter if the trenches get filled in?