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daz · 5th January 2008, 10:59 PM

Hi,
This is my first post here. I ended up here while trying to find some actual emperical information (rather than just standards/rules/hearsay) regarding trees and soil movement/house cracking/damage. I've read most of the online sources posted in this threads and found it all very illuminating if somewhat inconclusive. Where I live we have highly reactive clay soil (fairly deep - at least in places) over river silt. I guess there is something solid down there somewhere. We also have a lot of old Queenslander houses (I live in one) and a lot of trees (of various ages). The average queenslander seems to have stumps that are almost certainly not deep enough to get down to something solid, however house movement is something accepted in these houses (timber house, just flexes). We also had an extension built a few years ago with footings complying with the current regs (it has a huge volume of concrete going down 2.5m or more under each steel "stump"). However in the 70s a few blocks of brick flats were built in the area on floating slabs (I wouldn't be terribly surprised if they were under engineered for the amount of soil movement to be expected without trees). Such things are now not considered "in character" for the area but one of these is behind our place and has some cracking/movement issues.

So, I'm the evil neighbour with trees (trying to screen out a 70s brock box block of flats). The trees have been there longer than I have (15 years) but of course have grown. There are a couple of trees that I've said repeatedly to the flat body corp over the years they are welcome to cut down, but I have never sent them a reply that says "please come and cut down every tree in my back yard" (which, is what they ask for).

After I said that I wasn't prepared to let them just cut down anything that was growing and I wanted a list of the specific trees that their consulting engineer wanted removed I was given as "expert advice" a quote from an arbourist for cutting down every tree adjacent to the boundary. No offense intended, but I don't really think the advice given in that context is entirely "impartial".

Along the boundary are 2 tall trees, both of which are things I would happily get rid of - a Silky Oak and a Cadagi. There are also 2 smaller Acacia mearasii (I think) and a rather stunted Leopard tree (Caesalpinia ferren).

While they are only about 3m from the flats, I find it hard to believe that the Acacias will significantly contribute to the soil movement given all the other factors. I see that these trees are often used/recommended by Councils for planting as roadside trees etc. Surely this suggests they are not invasive/damaging?

Anyway - what do any of you think - do the Acacias need to go? And what screening plants can I use instead to "break up" the view of a 2 story block that runs the full width of my block and 2 of my neighbours blocks as well?

Thanks for any suggestions!

5th January 2008, 10:59 PM	#1 (permalink)
daz I'm new here so be nice Join Date: Jan 2008 Location: Brisbane, Australia Posts: 2	Re: Soil subsidence and trees Hi, This is my first post here. I ended up here while trying to find some actual emperical information (rather than just standards/rules/hearsay) regarding trees and soil movement/house cracking/damage. I've read most of the online sources posted in this threads and found it all very illuminating if somewhat inconclusive. Where I live we have highly reactive clay soil (fairly deep - at least in places) over river silt. I guess there is something solid down there somewhere. We also have a lot of old Queenslander houses (I live in one) and a lot of trees (of various ages). The average queenslander seems to have stumps that are almost certainly not deep enough to get down to something solid, however house movement is something accepted in these houses (timber house, just flexes). We also had an extension built a few years ago with footings complying with the current regs (it has a huge volume of concrete going down 2.5m or more under each steel "stump"). However in the 70s a few blocks of brick flats were built in the area on floating slabs (I wouldn't be terribly surprised if they were under engineered for the amount of soil movement to be expected without trees). Such things are now not considered "in character" for the area but one of these is behind our place and has some cracking/movement issues. So, I'm the evil neighbour with trees (trying to screen out a 70s brock box block of flats). The trees have been there longer than I have (15 years) but of course have grown. There are a couple of trees that I've said repeatedly to the flat body corp over the years they are welcome to cut down, but I have never sent them a reply that says "please come and cut down every tree in my back yard" (which, is what they ask for). After I said that I wasn't prepared to let them just cut down anything that was growing and I wanted a list of the specific trees that their consulting engineer wanted removed I was given as "expert advice" a quote from an arbourist for cutting down every tree adjacent to the boundary. No offense intended, but I don't really think the advice given in that context is entirely "impartial". Along the boundary are 2 tall trees, both of which are things I would happily get rid of - a Silky Oak and a Cadagi. There are also 2 smaller Acacia mearasii (I think) and a rather stunted Leopard tree (Caesalpinia ferren). While they are only about 3m from the flats, I find it hard to believe that the Acacias will significantly contribute to the soil movement given all the other factors. I see that these trees are often used/recommended by Councils for planting as roadside trees etc. Surely this suggests they are not invasive/damaging? Anyway - what do any of you think - do the Acacias need to go? And what screening plants can I use instead to "break up" the view of a 2 story block that runs the full width of my block and 2 of my neighbours blocks as well? Thanks for any suggestions!