Large conifer stump on/near footings area

[saveasteading]

You teased me into looking up the tables. Cypresses are high water use....and a felled tree is often a leylandii....so maybe.

Other conifers are listed as medium demand. 

 

Anyway a long dead tree has zero demand. 

 

And I thank you as I had never noticed the chart for distance from London. 50mm less every 50 miles.  I don't remember that being in the original BS document. 

 

My hunch is you will end up with 1.5m depth close to the stump, and less elsewhere (depending on the other trees....but rowan is low demand.

[Deejay_2]

14 minutes ago, saveasteading said:

No , it would mean 2.4m footings which is about 1/3 the cost of piles.

But if we (or SE or bco) discount the long dead tree then everything is shallower. I think I would discount nhbc depths for the dead tree as the ground has had 2 winters to recover.*

But I would locally take the footings below tree roots.

 

* I have done this several times, the difference being it was my decision and I was there to see the circumstances.

No it isn't. Do you know what type of conifer? Some have very little effect.

I've looked at the distance calcs on the NHBC website and WOW what a difference that makes with a moderate water demand tree - no mention of an SE design and suggesting a trench depth of 1.85 m so with some reinforcing rods a 2m depth might be acceptable for the full length of the elevation with the stump.

 

It does give coniferous trees in both high and medium demand tables but I agree with you that it has been felled 2.5 yrs and has probably died and won't be needing that much water.  I'm sure it was a leylandii tree and it was about 20 m tall. The tree in the church grounds is 10 m away - 20 m tall and is the same variety.

 

Thank you so much for pointing this out to me - absolutely great advice.

 

 

[saveasteading]

The thing about a practical SE is that they are quite likely to say that the dead tree is irrelevant, where a bco might not.

I see where the worry about engaging an SE comes from..the nhbc implies that you need an SE for deep founds and that an SE will design piles.  Not so. An SE will specify only what is required, and that is probably mid depth standard footings.

[SteamyTea]

On 29/04/2023 at 16:54, Deejay_2 said:

Diesel maybe

Really

 

https://www.gov.uk/contaminated-land

[Mr Punter]

The issue when the tree is dead is clay swell / heave but unlikely after 2.5 years.  Get the stump ground out and bridge over with reinforced concrete ground beam to SE design.

[Deejay_2]

12 hours ago, Mr Punter said:

The issue when the tree is dead is clay swell / heave but unlikely after 2.5 years.  Get the stump ground out and bridge over with reinforced concrete ground beam to SE design.

Thank you.  Are you recommending grinding out the stump in preference to removing the whole stump and roots where accessible with a digger (if that's possible). 

 

The stump removal man who came out yesterday to quote said he thought a digger would not be able to do the job.  He would grind out the stump and put the shredded material back in the hole so there is nothing to take away (which sounds unsatisfactory to me). 

 

As well as the foundation we also have a drain running along this elevation.  My thinking at the moment is to try with an excavator with an appropriate fitting and if that works refill the hole with the soil from the trench which is to be dug at the opposite side of the site.  This will have time to settle and be constantly refilled and compacted until we are ready to recommence the build in the future.  At the moment we just want a commencement notice. 

 

So to remove the whole stump and roots or grind down the stump - that is the question .......

 

 

[Dave Jones]

if you can remove it with a machine, its likely that wall will come down behind it though.

 

Grinding just removed the top part from sight, the reason he was leaving you the arisings was so he didnt have to pay to tip them.

 

Either way when it comes to digging the footings the bottom of the footing has to be deeper than any roots visible. Hire in the largest machine that you can fit, ideally a 13 tonner but nothing less than 5.

[saveasteading]

Do not backfill with the chippings. Not suitable next to the building. Put them in bags then either use as mulch or to brown bin, or to the garden waste at the tip.

Backfill with stone, tamped hard.

[Deejay_2]

42 minutes ago, saveasteading said:

Do not backfill with the chippings. Not suitable next to the building. Put them in bags then either use as mulch or to brown bin, or to the garden waste at the tip.

Backfill with stone, tamped hard.

When you say backfill with stone, do you mean stone chippings.  We have a lot of stone left over from rebuilding wall with bags full of smallish pieces.  I guess if we used these they will likely have voids and move over time.  So can you clarify please which stone is suitable.

Many thanks.

 

 

[saveasteading]

1 hour ago, Deejay_2 said:

which stone is suitable

Personally, I would get some type 1 or ballast even. Whack it down with a tamper. Then it will support the footings and wall, will not wash out, won't act as a soakaway,  and you can dig neatly through it without collapse.

If you use hardcore it might be fine but I can't say without seeing it. You are looking for something solid without voids. You could poss mix your stones up with some grit or sharp sand.

[Deejay_2]

Just to say that the experienced groundworker is coming this week to take out the tree stumps with his machine - or he will at least give it a go without damaging the wall.  I asked if the hole remaining could be used as a trial pit for a soil test as there would then be less disturbed ground.  He said no as there would be roots and stuff in it - not sure that makes sense.

What he went on to say is "you need to get rid of the stumps and then fill in the hole as though they were never there otherwise we'll run into problems, like last time, with them wanting deep trenches."  (The Stump Remover man said much the same in that he whipped out trees before getting involved with Building Control on his own project).

I said the BCO has already seen the tree stumps and specified deeper trenches but we need a soil test to check out the plasticity first.

Surely it's in my own interest to make sure we get the footings right to avoid future

problems.

Anyway I will report back on the attempts to extract Mr Stumpy from our garden.

[Carrerahill]

On 29/04/2023 at 15:03, Deejay_2 said:

We are about to remove a very large tree stump from our site.  The stump is/was a conifer of approx 20 m in height which was felled 2.5 yrs ago and stump killer applied at that time.  

I am attaching photos to show how near this 90 cm stump is to an old stone boundary wall and the tape on the ground shows approx where the wall of the one storey new building will sit.  The stump is encroaching where the trench will be by several cms.

My questions are:

1. Should the groundworker attempt to remove the whole stump.  Have the tree roots had time to die back.  Is this even possible.
2. The tree stump is almost touching the stone wall which we need to preserve and the digger may be unable to remove the whole root ball, so is it possible to do half and half ie remove as much as possible of the stump which lies over the footing area and then grind down the remainder as necessary.
3. Does anyone have suggestions about how to measure the depth of the trench fill foundation that might be required in a situation like this.  This proximity of a tree is not covered in the NHBC calculation table as far as I can see.  I have worked the depths out for the rest of the foundations but am "stumped" on this one.

Any help will be much appreciated. (Sorry, I could only upload one photo - I'm useless at this).

 

We had an issue like this last summer, an old Cherry tree stump right in the middle of a proposed wall, tree had been down for 5-6 years, I was sure it wouldn't move, but thought it might break up, so tried with a narrow bucket on a 1.5T digger and the stump just laughed at me, we did not want to dig it out as it was going to screw up an awful lot either side, so we got a stump grinder man in, he ground out a channel through the whole stump and root system at that point, and then we dug down to the same level as the rest of the trench before/after it. 

 

The foundation was wide as it was but we cut the channel wider at the point of the stump so the roots were back enough, then placed formwork to keep the concrete from widening out too much. A year later and soil and stone and bits have back filled the gap and roots randomly jut out the ground either side of the foundation but about 300mm back from where any wall will be, by the time this gets back filled with stone the roots will just rot away and be sequestered into the soil being no different to a root in a garden near a wall being left to rot.

 

My initial plan was actually to burn it out, build a little bonfire either side and over the stump and set it on fire, I was game, neighbour was not so keen.

Edited May 2, 2023 by Carrerahill

[SteamyTea]

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

I think it is what they used to do to cap mineshafts down here.

Now they put a metal cage over them. Then send the dogs down.

https://www.cornwalllive.com/news/cornwall-news/dogs-rescued-after-falling-porkellis-8123356.amp

[Deejay_2]

44 minutes ago, Carrerahill said:

We had an issue like this last summer, an old Cherry tree stump right in the middle of a proposed wall, tree had been down for 5-6 years, I was sure it wouldn't move, but thought it might break up, so tried with a narrow bucket on a 1.5T digger and the stump just laughed at me, we did not want to dig it out as it was going to screw up an awful lot either side, so we got a stump grinder man in, he ground out a channel through the whole stump and root system at that point, and then we dug down to the same level as the rest of the trench before/after it. 

 

The foundation was wide as it was but we cut the channel wider at the point of the stump so the roots were back enough, then placed formwork to keep the concrete from widening out too much. A year later and soil and stone and bits have back filled the gap and roots randomly jut out the ground either side of the foundation but about 300mm back from where any wall will be, by the time this gets back filled with stone the roots will just rot away and be sequestered into the soil being no different to a root in a garden near a wall being left to rot.

 

My initial plan was actually to burn it out, build a little bonfire either side and over the stump and set it on fire, I was game, neighbour was not so keen.

Hi - I am having difficulty imagining this but will copy it and print off to see if anyone can relate it to our stump.  At least it proves there's a way around it.    Thank you.

[Carrerahill]

3 minutes ago, Deejay_2 said:

Hi - I am having difficulty imagining this but will copy it and print off to see if anyone can relate it to our stump.  At least it proves there's a way around it.    Thank you.

You basically, you dig you trench, then get a stump grinder in to basically grind a route through the stump and all root systems etc. it more or less leaves a channel through the stump, below the root ball will be soil again, dig that out, you have a trench through the old stump position. 

 

We were then left with a trench that was a bit wider in the middle, so we used timber to create some form work to keep the foundation the same width the whole way along. 

 

We now have a 1000mm foundation the whole way down, even though the stump area was maybe 1400mm wide. 

Edited May 2, 2023 by Carrerahill

[Deejay_2]

3 minutes ago, Carrerahill said:

You basically, you dig you trench, then get a stump grinder in to basically grind a route through the stump and all root systems etc. it more or less leaves a channel through the stump, below the root ball will be soil again, dig that out, you have a trench through the old stump position. 

OK - got it!!    We are to going to attemp to remove the tree stump long before digging the trench which is why I couldn't quite get it.  I suspect we shall also need a stump grinder.

Thank you.

[Carrerahill]

9 minutes ago, Deejay_2 said:

OK - got it!!    We are to going to attemp to remove the tree stump long before digging the trench which is why I couldn't quite get it.  I suspect we shall also need a stump grinder.

Thank you.

In that case, I would call the grinding man first (try tree surgeons etc.), he has done this 1000 times before, tell him what you want to achieve and he will advise, he might want you to dig down a bit either side so he can get right in, ours was fully exposed when our guy came and he just chewed through it all by steering the tracked grinder at it with a big spinning, highly lethal looking cutting head. 

 

You can hire them too, but probably more hassle (and that is coming from me who DIY's everything).

[saveasteading]

2 hours ago, Deejay_2 said:

roots and stuff in it - not sure that makes sense.

He is right. The ground has been disturbed. Only gives an indication of the ground conditions.

I wouldn't be getting lab tests done. The ground will be typical all around the area and an SE or bco can tell by inspection.

 

However, when your tree hole is dug, do poke at it, and take pictures for us here. And no reason why you can't take a sample. Dig a neat lump out and put it in a sealed container.

 

[Deejay_2]

3 hours ago, saveasteading said:

He is right. The ground has been disturbed. Only gives an indication of the ground conditions.

I wouldn't be getting lab tests done. The ground will be typical all around the area and an SE or bco can tell by inspection.

 

However, when your tree hole is dug, do poke at it, and take pictures for us here. And no reason why you can't take a sample. Dig a neat lump out and put it in a sealed container.

 

After your comment I emailed the BCO and he confirmed that they will inspect the trial pit and will request a soil test only if necessary.  So thanks for that, all being well you have just saved me £70 incl p&p.  

[Deejay_2]

Update

I'll dispense with all my frustrations this week, mainly getting groundworker to give a firm day/time and then awkward BCO tel con when he was very offhand with me.  In the end, the trial pit excavation this morning and the inspection by the BCO turned out to be a pleasant experience.

 

So two trial pits were dug to 1.2 m this morning.  The ground is loam and is great, therefore no problem with the tree roots from the trees in the churchyard.  The BCO was lovely and helpful when he came out to inspect and is allowing us to dig a trench the length of one side of the elevation - he emphasised that this is a concession to enable us to have deemed to have commenced work before 15 June. 

 

Digger man coming next week to backfill the trial pits and dig one elevation trench 8 m x 1.2 m depth (BCO said all trenches to be 1.2 m deep unless we hit anything unusual).  Therefore no especially deep trenches where the stump is.    He says once dug, we can't backfill the trench we are digging as this would in effect mean we had not "started" so at the moment we intend covering the 8 m length with OSB boards and strong plastic sheeting.  (I suppose we could backfill once we have confirmation of commencement?)

 

The digger man will also excavate around the tree stump as much as possible and then, I think, get stump grinder man in. He doesn't seem phased with it at all.

 

All in all a successful day and fantastic news about the loam soil. From this experience I would say trial pits are a must.

 

I'll report further next week after trench is dug and tree stump out, hopefully with photos.

 

 

[saveasteading]

2 hours ago, Deejay_2 said:

the loam soil

Bag that up with a bit of fertiliser and sell it as John Innes compost to clay areas.

So, non shrink soil, dead or distant trees. 1.2 may not be necessary but i wouldnt argue. Good news, well done.

[Jilly]

You don't need to be a man to self build, but you do need to have balls...

[The Reverend]

Hi Deejay,

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.

The stump will eventually rot and it is likely that some minor settlement will occur so a lintel will allow for that, the second option is to stump grind all the way though but I estimate from the diameter of the stump that it could be 5-6 feet down.

[gaz_moose]

put all of the saw dust created from grinding the stump into sturdy black bin bags and advertise it on market place. i filled 20+ bags and gave them all away, i could have given 100 bags away.

if you can dig around the stump the grinder will be able to reach a deeper depth.

 

i have a similar predicament so am watching to see how you get on. i think the digger bucket will snag on all the old roots and rip the ground to bits leaving terrible trenches.

Edited May 7, 2023 by gaz_moose

[Gus Potter]

On 30/04/2023 at 11:51, Deejay_2 said:

I assume engineer designed would mean piles, so if I employ a SE he may be "duty bound" to say piles are necessary because of the requirements of NHBC.

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.