Cherry Plum removal on clay before building?

[William Clifford]

Hi all,

 

I was called to a property to quote for some work which included the request to take this Cherry Plum down in stages due to a garage being built in approx 3 months. The advice to remove the tree in stages had been given by a surveyor I believe. The garage will be roughly this side of the wooden shed seen in the pic. The homeowner told me that the ground is clay.

 

I advised that it is no longer advisable to remove a tree in stages, but was asked the following questions:

 

- Would the recently built extension (nearest the car) be at risk of heave if the tree was removed in one go? I felt that the risk was very small, but that it also depends on the foundations and that there is no definite answer. 

 

- Would it be best to remove completely before the garage is built?

 

- Should there be a period of time allowed to pass between felling and building?

 

- Is it best to leave the tree in and build?

 

I would think that it would be best to remove the tree first (though it is no sizeable monster), and allow the ground time to adjust to the tree not being there before building the garage- how long would this take? And in relation to the present extension, expect not to suffer from heave but this cannot be guaranteed of course.

 

Opinions and advice please?

 

Thank you.

 

 

[Gary Prentice]

Unless you can predict the rainfall for the next few years and have enough geological knowledge to know the ability of the soil to absorb water if there's an existing SMD, steer clear. 

 

With the the existing garage, haven't they designed the foundations to take into account the tree anyway? The footings should be deep enough to be below the influence of the trees roots and some anti- heave precautions already incorporated if the soil type indicates they're needed.

[Khriss]

Frankly the garage would be better built on pile-n-beam foundations, then you can forget abt soil heave/shrinkage. Mini piles ain't dear now. Good to see you yesterday Gary * waits fr 'that  Khriss ! Just ponced my fags n ate all of the biscuits' *  K

[Gary Prentice]

Not at all Khriss, we had some interesting discussion. 

 

I'm still not sure about the hat though! 

[Khriss]

Quite simple - stops bird an bat shit falling in my eyes  K

[William Clifford]

The homeowner has said that the current extension has foundations to a depth of 1 meter and that the new garage will need foundations to 1.5 meters according to the survey. I / we are not sure what type of foundations. I don't claim to know anything about buildings and have said this to the client suggesting she asks the builder if they think the extension has been built to take the tree and soil type into consideration. She felt that as the building regs visited site and said that 1 meter was enough, that they would have taken these things into account. The result is that the tree has been removed Monday, with an email to me clarifying that they have requested for me to remove the tree and that I haven't given any assurances or otherwise about the affects of the tree roots and the removal on the building. Indeed, I have said it is impossible to give any guarantees either way, so, decision has been made.

 

Thank you for the input!

[Gary Prentice]

Thanks for the update. Sounds like you handled everything correctly to avoid any future comebacks. 

 

The problem is that everyone looks to everyone else to blame if problems occur later. The tree people, us, should only be providing tree information for the structural engineer, who hopefully has information on soil type and shrink/swell potential. 

 

They then do the calculations for the potential of vegetation to cause subsidence if retained/heave if removed and design the foundations accordingly. They are the ones that tell the builder what foundation depth/design should be and provide that information for the building regs people to sign off. 

 

Saying that, I asked a structural engineer recently where he'd got his information from, regarding a sites shrink/swell potential, as it differed from mine. His company used a moderate potential, as an average for the area, rather than get proper tests to confirm BGS mappings low potential. Maybe no big deal, but on that site I'd imagine it would add a good few thousand pound to the foundation cost.