Soil subsidence and trees

dguntertrees · 22nd July 2008, 08:49 PM

Thanx Eric

Galbee · 23rd July 2008, 05:29 AM

Hey they are actually doing something pro-active for trees at last, im surprised that the london boroughs are setting the standard on this, but there may be a chance that the rest of the country will follow suit and then you never know europe, the western world. fingers crossed.
as usual Eric thank you your a star.

Done it · 15th February 2009, 12:34 AM

Quote:

Originally Posted by Done it

Yep, blame the trees. Our house is just an old 50's timber, surrounded by trees [I have posted some pics in that tree hugger thread] it creaks & groans, when it rains the back door jams, when it's dry the front door jams, it's clay/shale around here & brick houses crack, trees or no trees. Do you think people will listen, no way. I just get sick of trying to explain it.

Well, we've had some RAIN. All day & all night.

If I could get the back door open I'd ????

dirtguy · 12th March 2009, 02:33 PM

I'm coming late to this discussion, but can't resist dredging this thread back to the top because expansive soils have been a hot button for me for a long time. BTW, being a registered geotech I have license to pontificate...

At least here in the states, builders are so short sighted that it takes an act of congress to get them to spend a little more money on their foundations. My opinion is that, if you have soils that are so highly expansive that relatively minor changes in moisture content can cause settlement on the order of inches (cm for you brits and aussies), then you shouldn't be screwing around with trying to deal with it by maintaining constant moisture content!!! There are too many unpredictable things that can screw up the moisture content balance; a water pipe breaks, a tree dies, somebody upgradient causes a change in groundwater flows, somebody changes watering patterns for a period of time... Where any of these unpredictable events can cause structural damage running to the multiple tens or even hundreds of thousands of dollars, why screw with it??? Bulk up the foundation, people. An ounce of prevention and all that...

In Denver, Colorado there are huge problems with expansive shales. It is common practice there to build structures (even single family homes) on drilled pier foundations. In southern Cali, where expansive soils occur, it is common to use post-tensioned slabs, drilled piers, or other special foundation systems. In these areas, people have learned by sad experience that it's not worth it to take the lowest first cost approach to construction. Other areas, still need to catch up to that way of thinking.

In the case at the top of this thread, I don't see how cutting the trees down is a long-term solution to the expansive soil problem. In fact, you're going to induce more differential ground movement by tree removal. Why not leave the trees alone and deal with the root (no pun intended) problem -- the poorly planned foundation system?

newguy18 · 12th March 2009, 03:57 PM

Around here its push evry tree over then devleop,or develop in the middle of the woods with trees right up against structures[sometimes growing onto strucures].Plus bull doxers aren't exactly friendly to the remaining tree's root systems and they usually die within 2 years.

Eric Frei · 25th June 2009, 08:23 AM

Some more from the UK.

FT.com / Personal Finance - Subsidence claims expected to rise

Quote:

Subsidence claims expected to rise

June 24 2009 15:52

After the two wettest summers since records began the UK is finally experiencing a heat wave. But while this is good news for sun-worshipers insurers are warning that the hot weather will bring with it the risk of subsidence.

Incidences of subsidence increase in dry, sunny weather, as vegetation in the garden grows more quickly and requires more moisture. The movement of the soil beneath the foundations of homes can create thousands of pounds worth of damage to the home.

Halifax Home insurance says homes in the south east are likely to be more at risk, because of the warmer temperatures but warns that warm conditions predicted throughout the UK could mean subsidence is more likely for everyone.

Figures from the Association of British Insurers show that the insurance industry has dealt with 144,000 subsidence claims over the last four years alone, costing over £800m.

“Signs that a property might be suffering from subsidence include cracks in walls, particularly if they start from the corners of windows or doors which themselves may become difficult to open or close,” says Neil Curling, Halifax Home Insurance senior structural claims manager. You may also begin to see cracks appearing in the soil.”

He urges homeowners to take steps to reduce the risks to their property such as when buying a house to check for historical activity such as mining as 15 per cent of subsidence claims are due to previous mining activity.

Curling also recommends homebuyers check the property drainage as subsidence can be caused by water leakage into the soil - 15 per cent of subsidence claims arise from water washing away finer soil in the ground.

Another way to protect your property is to ensure trees are not too close to the outside walls. Tall trees too close can be an issue, particularly for homes built on a clay subsoil

“Tall trees close to the house can be bad news, particularly for homes built on clay subsoil. They take water out from the ground and cause it to shrink and move. Tree removal solves 84 per cent of tree-related subsidence claims.”

If you are concerned about subsidence the sooner you contact you home insurance provider the better so that appropriate action can be taken.

Eric Frei · 13th December 2009, 07:45 AM

The terminolgy was gained from govt sources, perhaps you'd like to contact them.

Two are listed in this post.

Tree & Root Damage

Eric Frei · 5th April 2010, 07:12 PM

Another case or two brewing involviing council trees in front of houses in Ottawa Canada.

The roots of conflict

Quote:

The roots of conflict

A 15-metre ash tree stands as a challenge to the city's urban tree bylaw, reports

By Neco Cockburn.April 5, 2010 12:00 AM

Ira and Leigh Bridger probably wouldn't mind if the 15-metre ash tree on city property beside their south Ottawa home was killed by lightning, disease or emerald ash borers.

The couple say the tree is damaging their home's foundation and want it removed, but the city won't cut it down.

The Bridgers filed a lawsuit last year and hope they're helped by a recent case in which an Ontario Superior Court judge granted an injunction requiring the city to remove a large silver maple tree that was damaging a home's foundation.

That ruling appears to be the first court decision involving the way the city tries to preserve urban trees, and it challenges a bylaw that doesn't allow the removal of a healthy city tree for causing foundation damage. The city is appealing the case and is seeking a stay of the order to remove the tree, saying that, once a ruling is made, lawyers will be better able to assess the city's legal position in six other tree cases that are before the courts. One of those cases involves the Bridgers.

The bylaw is intended to protect the declining urban forest and loss of mature trees, but the Bridgers say it should be amended, that it's too broad and doesn't provide a "common sense" solution for trees that are damaging residents' homes.

"Why would city councillors continue supporting a management practice that already has, and could continue to, cause serious damage to its own citizens' property?" Ira Bridger said.

They say they have already spent $115,000 to fix the foundation on an addition to their house, but more repairs are needed.

Until the tree is gone, there's no guarantee the situation won't get worse and there's no way anyone would buy the house after learning of the potential troubles, the Bridgers say.

A report from Golder Associates, the firm hired by the Bridgers' insurance company, concluded the foundation distress was caused by "moisture depletion of the silty clay subsoil caused by the water demand of the large ash tree."

In October, the firm said in a follow-up report that the tree's root system extended beneath the existing foundations of the addition and the "continued growth of the tree does pose the risk of future damage to the original foundations."

The city has installed watering tubes and offered to pay for half of the repairs, but the problem won't be solved until the tree is gone, the Bridgers say, adding they have recently seen new cracks in their kitchen walls.

"It's not an accident, it's not an act of God. It's preventable," Leigh Bridger said.

The city used to remove its trees if neighbouring property owners asked and the tree was proved to be causing soil shrinkage and foundation damage.

The policy was reviewed and in 2005 council approved a report that recommended that a tree be retained even if it was contributing to foundation damage and mitigation measures such as watering and trimming couldn't guarantee that future damage wouldn't happen, according to the recent court decision.

A bylaw was enacted and the city hasn't removed one of its trees for foundation damage since 2005, according to the ruling, which says 147 trees are now on the city's special watering program.

The Bridgers have lived in their Fontenay Crescent home since 1995 and in 2000 started to build an addition for Leigh Bridger's mother, who has health problems, they say.

In 2008, Ira Bridger saw cracks in the foundation wall in the addition's basement floor and told the city, he says. The floor in the addition started to slope, he says.

In court documents, the city argues the tree "is a natural use and as such does not constitute a nuisance."

"City of Ottawa trees make up the urban forest and promote environmental, health, economic and aesthetic benefits for the community as a whole," says a statement of defence to the Bridgers' claim.

The city says it puts the Bridgers to "the strict proof" that the tree caused "subsurface moisture depletion" and the home to settle.

In the alternative, the city says any settlement of the home would have occurred naturally over time, possibly because of factors outside its control, such as wind and sun.

The home and addition were not "properly constructed given the natural phenomena which could, or did, affect it," the statement of defence says. The city also says its tree bylaws and policies have been made "in good faith exercise of discretion to maintain trees and green space."

The Bridgers say the addition was built to code and underwent a city inspection. They're seeking $430,000 in damages and an order for the tree's removal, similar to an order that was granted in the recent court decision involving a city tree.

In that decision, the judge rejected the city's arguments and said the city's policy in favour of healthy and mature trees was generally good for the public, but, in light of the tree's size, nature and proximity to the foundation, the harm to the homeowners was "greater than ought to be required of them."

Some key points are the city acknowledges the problem and has

Quote:

147 trees are now on the city's special watering program

which is re-hydration to prevent subsidence.

If there was a "standard" for foundations like here in Australia, then the Bridger's would have a much easier case. Here for example if you build on say a class H clay the rule is whatever the tree height is the distance it has to be from the house. As the house was there first and the tree grew to violate that specification then the council would become liable ... they could install root barrier or as they have a re-hydration system .... however there's no guarantee that either is bullet proof.

In other locations more data would be collected, soil core analysis and moisture content to determine the effect of the tree upon the soil.

I know I have told many customers to put councils on notice about their footpath trees and request root barrier installation, after all it's their tree causing damage to your asset, deliberately planted.

Eric Frei · 2nd May 2010, 09:17 AM

The council finally complied.

CTV Ottawa- Ottawa couple wins fight to remove destructive tree - CTV News

Quote:

It took tens of thousands of dollars in legal fees and public criticism, but an Ottawa couple finally won a battle to get a 15-metre ash tree, on Ottawa city property, next to their home removed.

The sprawling roots caused $120,000 in damage to the foundation of Ira and Leigh Bridger's south Ottawa home.

The couple contacted all 24 councillors about his tree problem, but only eight responded. It's believed the city is dealing with another half-a-dozen cases like this one. The tree will be removed on Wednesday.

Although the couple did sue -- a two-year-long legal battle -- the city agreed to take the tree down just one day after public outcry over a similar case that cost $140,000 in taxpayer legal fees.

In that case, a 16-metre silver maple tree caused foundation cracks in a York Street home; the city lost its battle against the homeowners in court.

Coun. Rainer Bloess has told CTV Ottawa the city has to stop letting the court make the decisions for them.

The City of Ottawa paid $140,000 in legal fees before removing a tree in front of this home on York Street. The tree near the Bridgers' will be removed Wednesday.

Birkozo · 22nd May 2010, 05:39 AM

I was accused by you with not having posted any reply. You were quite right, let me make amends. I was going to buy a house near Brisbane on a new estate, but as soon as I queried the building practices and ethics of one of Australia's star builders, my deposit was promptly refunded by its CEO.

When trees and buildings need to coexist on tiny plots, correct building practices must be followed and enforced, which do not seem to be the case.
Not only houses crack and sink, but many trees loose their lives unnecessarily. Take a real life example. The rock strata under a house, was 1,6m. It was covered by loose clay soil known for its instability with varying moisture content. The "consultant", who was employed by the builder, recommended a waffle construction "with" or "without piers". No wonder that the builder chose the latter, though the the piers would have added little to the total cost of the building if correct drilling equipment was available. The steel reinforcing in the waffle structure drawing reproduced by the consultant, according to him, from the Australian Standard Spec, was incorrect. No root barriers were constructed. Soon after completion the house started cracking and the complaint by the owner met with all kinds of pathetic excuses by the builder and his "consultant". Eventually several beautiful trees were removed. Had the foundation been constructed correctly the trees would be still alive today. There must be thousands of cases like this, which suggests that Australian building practices need to be overhauled and councils should have the mechanism to check if builders followed them. Australian builders could learn the elements of building from the Bible, that houses should be built on rock and not on sand.

Eric Frei · 22nd May 2010, 07:15 AM

Hey Birkozo,

Have you posted elsewhere here or something?

On the recent thread and video of the large tree we felled, not only did BCC get the TPZ very wrong but again the builder made no foundation changes and building was approved for a pretty much standard on ground slab. It was only when I got involved that all could see the errors.

Now the tree was always on the block, so from word go everybody stuffed it up.

treeshaveneeds · 10th June 2010, 03:39 PM

Great set of articles Ekka.

If, a concrete root barrier is such a great tool, why not require it to be installed around all new house construction. It seems to me the wall wouldn't add much to the overall cost of the new house. Environmentally, trees and houses could live in harmony, and people would benefit.

Obviously, we need to change the way people think. Perhaps the younger generation - green thinkers -- will insist on this kind of forward thinking, or the houses won't be bought.

We can only hope.

Brent

treeshaveneeds · 10th June 2010, 04:13 PM

Bob Wulkowicz post # 46? Jan 31 2008 noted that

Quote:

And as to structures and buildings, with Secondary or Radial growth which is the increase in diameter along the length of a root,

...the forces generated are not sufficient to displace loaded structures such as dwellings, or to force apart brickwork or drainage pipes.

I agree with virtually everything Bob wrote, both as common sense and from experience.
But, I had an experience 2 years ago that gave me pause how an unusual circumstance could cause a buckling of the wall of a structure - probably enhanced by root development. The bungalow had a downpipe half way down the length of the building, and within 2 feet of a Black Walnut tree. The water was allowed to seep beside the building, and whether the water created a void beside the building (though the clay had nowhere to go), or the root responded to a great source of water - which seemed most likely, and end result was a massive root on that side, extreme soil compaction (clay) and a buckling of the basement wall 4-6 feet below grade. I think it was too deep for frost/ice pressure to form (Toronto, Ontario isn't usually super cold, for long periods), and so I believe, in this special case, the tree root created sufficient pressure (along with the excess water softening the foundation) to buckle the wall.
The house was torn down, and the tree root had to be cut out by hand (by me) and the soil density was extremely high. Unfortunately I didn't measure the density or keep a sample, but the structure of the clay was extremely blocky, and even wet, had little plasticity.

So I would have to say, under extremely unusual circumstances, wall buckling and other displacements are possible. But this is the rare occurrence - not the norm.

And in the old days, clay pipe was used for sewer connections from the house to the street or to the septic field. And with the softening of the clay, and the nutrient source available for the roots, these pipes did break apart with expanding roots - but only after many, many years in the ground.

To say, with utmost certainty, roots never do this - is a bit reckless. But to say the occurrences are extremely rare? I heartily agree.

The thread was well worth reading. Thanks to all who participated. Brent

Eric Frei · 10th June 2010, 10:06 PM

Quote:

Originally Posted by treeshaveneeds

Great set of articles Ekka.

If, a concrete root barrier is such a great tool, why not require it to be installed around all new house construction. It seems to me the wall wouldn't add much to the overall cost of the new house. Environmentally, trees and houses could live in harmony, and people would benefit.

Obviously, we need to change the way people think. Perhaps the younger generation - green thinkers -- will insist on this kind of forward thinking, or the houses won't be bought.

We can only hope.

Brent

Dead right.

We are having ours revamped at the moment .... lets see if they were smart enough to build stronger foundations.

Draft AS2870 Residential Slabs and Footings Comment

22nd July 2008, 08:49 PM	#61
dguntertrees Semi-mature vigorous tree Join Date: Aug 2007 Location: Mudgeeraba, SE Queensland Posts: 82	Re: Soil subsidence and trees Thanx Eric

23rd July 2008, 05:29 AM	#62
Galbee Veteran Heritage Status Join Date: Jun 2008 Location: Brisbane Aus Posts: 1,315	Re: Soil subsidence and trees Hey they are actually doing something pro-active for trees at last, im surprised that the london boroughs are setting the standard on this, but there may be a chance that the rest of the country will follow suit and then you never know europe, the western world. fingers crossed. as usual Eric thank you your a star.

12th March 2009, 02:33 PM	#64
dirtguy Sappling Join Date: Mar 2009 Location: Oregon USA Posts: 16	Re: Soil subsidence and trees I'm coming late to this discussion, but can't resist dredging this thread back to the top because expansive soils have been a hot button for me for a long time. BTW, being a registered geotech I have license to pontificate... At least here in the states, builders are so short sighted that it takes an act of congress to get them to spend a little more money on their foundations. My opinion is that, if you have soils that are so highly expansive that relatively minor changes in moisture content can cause settlement on the order of inches (cm for you brits and aussies), then you shouldn't be screwing around with trying to deal with it by maintaining constant moisture content!!! There are too many unpredictable things that can screw up the moisture content balance; a water pipe breaks, a tree dies, somebody upgradient causes a change in groundwater flows, somebody changes watering patterns for a period of time... Where any of these unpredictable events can cause structural damage running to the multiple tens or even hundreds of thousands of dollars, why screw with it??? Bulk up the foundation, people. An ounce of prevention and all that... In Denver, Colorado there are huge problems with expansive shales. It is common practice there to build structures (even single family homes) on drilled pier foundations. In southern Cali, where expansive soils occur, it is common to use post-tensioned slabs, drilled piers, or other special foundation systems. In these areas, people have learned by sad experience that it's not worth it to take the lowest first cost approach to construction. Other areas, still need to catch up to that way of thinking. In the case at the top of this thread, I don't see how cutting the trees down is a long-term solution to the expansive soil problem. In fact, you're going to induce more differential ground movement by tree removal. Why not leave the trees alone and deal with the root (no pun intended) problem -- the poorly planned foundation system?

12th March 2009, 03:57 PM	#65
newguy18 Part of the Furniture Join Date: Jun 2007 Location: orlando,fl Posts: 5,206	Re: Soil subsidence and trees Around here its push evry tree over then devleop,or develop in the middle of the woods with trees right up against structures[sometimes growing onto strucures].Plus bull doxers aren't exactly friendly to the remaining tree's root systems and they usually die within 2 years. __________________ Have your say join us today. I ship USA saws out of the USA old schooler

13th December 2009, 07:45 AM	#67
Eric Frei Admin - Australia's most prominant Arborist - prev Ekka Join Date: Jan 2007 Location: Brisbane Posts: 10,775	Re: Soil subsidence and trees The terminolgy was gained from govt sources, perhaps you'd like to contact them. Two are listed in this post. Tree & Root Damage __________________ Free Online Tree Value Calculator by TreeWorld Free Online TPZ and SRZ AS4970-2009 Calculator by TreeWorld Free Online Tree Surface Area and Tree Volume Calculator by TreeWorld My businesses:- Qualified Brisbane Tree Lopping \| Stump Grinding Brisbane \| Brisbane - Gold Coast Consulting Arborist \| Project Arborist

22nd May 2010, 05:39 AM	#70
Birkozo I'm new here so be nice Join Date: Jan 2010 Location: Nairobi, Kenya Posts: 1	Re: Soil subsidence and trees I was accused by you with not having posted any reply. You were quite right, let me make amends. I was going to buy a house near Brisbane on a new estate, but as soon as I queried the building practices and ethics of one of Australia's star builders, my deposit was promptly refunded by its CEO. When trees and buildings need to coexist on tiny plots, correct building practices must be followed and enforced, which do not seem to be the case. Not only houses crack and sink, but many trees loose their lives unnecessarily. Take a real life example. The rock strata under a house, was 1,6m. It was covered by loose clay soil known for its instability with varying moisture content. The "consultant", who was employed by the builder, recommended a waffle construction "with" or "without piers". No wonder that the builder chose the latter, though the the piers would have added little to the total cost of the building if correct drilling equipment was available. The steel reinforcing in the waffle structure drawing reproduced by the consultant, according to him, from the Australian Standard Spec, was incorrect. No root barriers were constructed. Soon after completion the house started cracking and the complaint by the owner met with all kinds of pathetic excuses by the builder and his "consultant". Eventually several beautiful trees were removed. Had the foundation been constructed correctly the trees would be still alive today. There must be thousands of cases like this, which suggests that Australian building practices need to be overhauled and councils should have the mechanism to check if builders followed them. Australian builders could learn the elements of building from the Bible, that houses should be built on rock and not on sand.

22nd May 2010, 07:15 AM	#71
Eric Frei Admin - Australia's most prominant Arborist - prev Ekka Join Date: Jan 2007 Location: Brisbane Posts: 10,775	Re: Soil subsidence and trees Hey Birkozo, Have you posted elsewhere here or something? On the recent thread and video of the large tree we felled, not only did BCC get the TPZ very wrong but again the builder made no foundation changes and building was approved for a pretty much standard on ground slab. It was only when I got involved that all could see the errors. Now the tree was always on the block, so from word go everybody stuffed it up. __________________ Free Online Tree Value Calculator by TreeWorld Free Online TPZ and SRZ AS4970-2009 Calculator by TreeWorld Free Online Tree Surface Area and Tree Volume Calculator by TreeWorld My businesses:- Qualified Brisbane Tree Lopping \| Stump Grinding Brisbane \| Brisbane - Gold Coast Consulting Arborist \| Project Arborist

10th June 2010, 03:39 PM	#72
treeshaveneeds Mature tree Join Date: Jun 2010 Location: Toronto, Ontario, Canada Posts: 433	Re: Soil subsidence and trees Great set of articles Ekka. If, a concrete root barrier is such a great tool, why not require it to be installed around all new house construction. It seems to me the wall wouldn't add much to the overall cost of the new house. Environmentally, trees and houses could live in harmony, and people would benefit. Obviously, we need to change the way people think. Perhaps the younger generation - green thinkers -- will insist on this kind of forward thinking, or the houses won't be bought. We can only hope. Brent

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