Urgent Q about a tree/underpinning, any structural eng's in?

[schmokin1]

Hi All

Mods please don't move this to the homes/diy (yet) as i need an answer today, hopefully!

I have some underpinning about to start and my contractor/engineer is being unreasonable (IMHO) about whether a tree affects the depth requirements.

There is an ellwoodii tree over 30 years old, 7.6 m from the nearest corner of the structure to be underpinned. It is 5.5m height, taller than the norm of about 3m. The engineer insists it has to be considered as a leylandii or similar at 20m height, ie won't accept that it reached its final height donkeys years ago.

The engineer's supplied scale says height x 1.25 gives the distance that the tree affects. My contention is that although it's a bigger than normal tree, it is fully grown and therefore outside
the zone of influence.

Can anyone tell me who is correct? The extra depth he says I need will cost about 2 grand extra!

[Big Al.]

Would you like it moved yet?

[ALawson]

How are you going to move a tree?

[Rotary Madness]

ALawson said:

How are you going to move a tree?

Fire?

[paoloh]

schmokin1 said:

Hi All

Mods please don't move this to the homes/diy (yet) as i need an answer today, hopefully!

I have some underpinning about to start and my contractor/engineer is being unreasonable (IMHO) about whether a tree affects the depth requirements.

There is an ellwoodii tree over 30 years old, 7.6 m from the nearest corner of the structure to be underpinned. It is 5.5m height, taller than the norm of about 3m. The engineer insists it has to be considered as a leylandii or similar at 20m height, ie won't accept that it reached its final height donkeys years ago.

The engineer's supplied scale says height x 1.25 gives the distance that the tree affects. My contention is that although it's a bigger than normal tree, it is fully grown and therefore outside
the zone of influence.

Can anyone tell me who is correct? The extra depth he says I need will cost about 2 grand extra!

Do you employ the services of said engineer because he is an expert???

[NDA]

I general terms the largest extent of the branches is where the big roots will reach. So if there are no branches touching the house, the roots won't be interfering with the foundations.

Is the engineer appointed by an insurance company? What is he suggesting - the felling of the tree?

[elster]

ALawson said:

How are you going to move a tree?

Tractor "knocking over" trees can be quite common

[Tom_C76]

NDA said:

I general terms the largest extent of the branches is where the big roots will reach. So if there are no branches touching the house, the roots won't be interfering with the foundations.

Is the engineer appointed by an insurance company? What is he suggesting - the felling of the tree?

The above is absolute bull. A tree on a clay soil can affect the soil many metres beyond the root zone due to dessication.

A 30 year old tree could well grow larger, and if the species is unknown it should be treated as high water demand, as per Leylandi. That said, I've never heard this 1.25 x height used for underpinning, there are charts that relate distance from tree to required depth, taking into account species and clay type.

If you're certain it is an Ellwoodii varient, then it should indeed be full grown, but this is a cultivated variety of a tree that can apparently reach 60' high, so he may be being overly cautious.

Why are you having underpinning done if you don't believe the tree is the problem?

Edited by Tom_C76 on Sunday 12th July 18:18

[NDA]

Tom_C76 said:

NDA said:

I general terms the largest extent of the branches is where the big roots will reach. So if there are no branches touching the house, the roots won't be interfering with the foundations.

Is the engineer appointed by an insurance company? What is he suggesting - the felling of the tree?

The above is absolute bull.

Nice.

Anyhoo, in 'general' terms lateral roots are accepted by most to end at the branch dripline. There are exceptions and this is only a rule of thumb - certainly was when we had to consult tree surgeons during an extension building at home. Some tree guys reckon the branches grow laterally as far as the tree is tall - species and soil dependent I guess....

[paoloh]

NDA said:

Tom_C76 said:

NDA said:

I general terms the largest extent of the branches is where the big roots will reach. So if there are no branches touching the house, the roots won't be interfering with the foundations.

Is the engineer appointed by an insurance company? What is he suggesting - the felling of the tree?

The above is absolute bull.

Nice.

Anyhoo, in 'general' terms lateral roots are accepted by most to end at the branch dripline. There are exceptions and this is only a rule of thumb - certainly was when we had to consult tree surgeons during an extension building at home. Some tree guys reckon the branches grow laterally as far as the tree is tall - species and soil dependent I guess....

Anther load of total bull

[NDA]

paoloh said:

Anther load of total bull

Good innit?

[AstonZagato]

paoloh said:

NDA said:

Tom_C76 said:

NDA said:

I general terms the largest extent of the branches is where the big roots will reach. So if there are no branches touching the house, the roots won't be interfering with the foundations.

Is the engineer appointed by an insurance company? What is he suggesting - the felling of the tree?

The above is absolute bull.

Nice.

Anyhoo, in 'general' terms lateral roots are accepted by most to end at the branch dripline. There are exceptions and this is only a rule of thumb - certainly was when we had to consult tree surgeons during an extension building at home. Some tree guys reckon the branches grow laterally as far as the tree is tall - species and soil dependent I guess....

Anther load of total bull

's what our architect discussed with the tree people on the council when we built our garage and they accepted it.

[Tom_C76]

AstonZagato said:

paoloh said:

NDA said:

Tom_C76 said:

NDA said:

I general terms the largest extent of the branches is where the big roots will reach. So if there are no branches touching the house, the roots won't be interfering with the foundations.

Is the engineer appointed by an insurance company? What is he suggesting - the felling of the tree?

The above is absolute bull.

Nice.

Anyhoo, in 'general' terms lateral roots are accepted by most to end at the branch dripline. There are exceptions and this is only a rule of thumb - certainly was when we had to consult tree surgeons during an extension building at home. Some tree guys reckon the branches grow laterally as far as the tree is tall - species and soil dependent I guess....

Anther load of total bull

's what our architect discussed with the tree people on the council when we built our garage and they accepted it.

Like I said in my previous post, if it is a clay soil, which is likely if a tree is causing underpinning to be needed, the zone of influence of the tree is much greater due to the extraction of moisture from the clay causing shrinkage. On a non-shrinkable soil such as sand or gravel the tree can only cause damage by direct content between root and foundation, at which point finding the extent of the root spread is relevant.

OP, why is the underpinning required as this will help get the thread back to your problem rather more directly.

TC

[schmokin1]

Hi all

the underpinning is required as I am building an extension over a garage wall(slab foundation).

The ellwoodii is in the neighbour's garden. While the neighbour is OK with me cutting it down if I must, obviously they don't want an inoffensive tree felled for no reason.

Anyway I went to see the local Building control officer today who agrees with me (we had the soil type/tree type/distance tables out), so either the eng toes the line or I get a different eng/contractor.

Cheers all
Schmo