One of my neighbors has allowed a fruit tree to
grow past the roof line of our duplex. The tree
is next to our fence, and its branches touch our
roof. The biggest problem, though, is that the
roots are now at the edge of the bottom floor
of the duplex. This building foundation is slab
concrete. When we approached the neighbor, they
said we had to hire the arborist, and pay for
the work of cutting the roots (the tree would
probably top over), or removal of the tree (several
thousand dollars). What is the best approach?
I do not have the money for removing a tree.

Reply to post by Noel, on July 24, 2001 at 14:18:34:

If you have found a domestic fruit tree which would cost "several thousand dollars" to remove, you have likely found a National Champion Tree! I don't know where that figure came from, but it does sound ridiculous.As far as the remedy to the problem is concerned you may well need to take legal advice. James.

Reply to post by James Causton, on July 24, 2001 at 14:18:34:


One of my neighbors has allowed a fruit tree to grow past the roof line of our duplex. The tree is next to our fence, and its branches touch our roof. The biggest problem, though, is that the roots are now at the edge of the bottom floor of the duplex. This building foundation is slab concrete. When we approached the neighbor, they said we had to hire the arborist, and pay for
the work of cutting the roots (the tree would probably top over), or removal of the tree (several thousand dollars). What is the best approach?

I do not have the money for removing a tree.

______________________________________


It doesn't matter much if you have the money; it would undoubtedly be wasted if you remove the tree. Driven by an awful lot of silliness in the UK, the idea of destructive tree roots is starting to take root here the States and in the spread of urban myths that I consider more baseless and insidious than accurate or true.

The quarrels about limbs over property lines must go as far back as the invention of those lines themselves, and the squabbles will continue until Nature gets rid of us all in the slow-cooking crock pot she has planned.

As to the roots, that's a new lunacy born of not understanding that roots simply do not generate pressures enough to crack concrete or foundations. As to shrinking soils and cracking our vaunted construction, there are only a few specific kinds of clay where that can occur. Indeed, if your home turns out to be situated on that type of soil, find a lawyer--not an arborist--and take out after the developer. That would be money better spent.

Somewhere I have a picture of a heavily wooded area with the top soil washed away. The roots of all the trees are everywhere. It is a remarkable photo and if I can dig it up or if someone has a similar one, it would be useful here.

Implied in your description is that the tips of the canopy and the roots are both at the edge of your house--top and bottom. Both are small relatively and constitute more of an issue of trespassing than they do of any physical threat.

I think its a shame that we worry about these things, but I have been there myself and I can assure you it's not worth the aggravation. Get someone to trim the branches back a bit; leave the roots alone. There is a risk that the tree might be damaged to the point of being an eyesore or physically hazardous. Why take it to that end in a territorial dispute that results more from how we're squeezed together in cities and want to be left unintruded upon when we come back from jobs we hate?

What fruit does the tree have? Is it happy and bountiful? Geez, I'd prefer that as a neighbor any day. At least it doesn't leave beer cans on the lawn.


Bob Wulkowicz

Reply to post by Wulkowicz, on July 24, 2001 at 22:38:03:

Bob,Could you go into a little more
detail on roots not exerting enough pressure
to push in a foundation wall?I have seen walls
pushed in and cracked by what I thought were roots.
I have seen roots growing through walls,although
I suspect this would be from the root finding a
crack already in the wall. But back to the point,
if roots don't exert enough force than what
causes a foundation to bow in after many years
of a large tree growing 5 feet away?
Thanks,Bill

Reply to post by Bill, on July 27, 2001 at 17:40:00:


Bob,

Could you go into a little more detail on roots not exerting enough pressure to push in a foundation wall? I have seen walls pushed in and cracked by what I thought were roots.

I have seen roots growing through walls, although I suspect this would be from the root finding a crack already in the wall. But back to the point, if roots don't exert enough force than what causes a foundation to bow in after many years of a large tree growing 5 feet away?

Thanks, Bill

________________________

I apologize for the delay in getting back; I didn't know you had responded.

There is a simple biological truism I tend to agree with in my old age; if something that intends to grow, destroys itself in the process, it won't grow any more. And usually Mother Nature respects that lesson and as a consequence, her creatures are really smart about those issues.

So, if the growth of a root is going to have enough generated pressure to crack concrete, the internal mechanisms of the cell (the cell itself) also must be able to generate and grow inside that same pressure. Since most, if not all, living things can't take the pressures required to compress or crack concrete, they don't do it. Concrete strength in residential work according to specs can be about 4000 psi and high-strength commercial concrete can go up to 15,000 psi easily. To affect those concrete strengths, an attacking root tips must operate in those ranges and must divide cellularly at that pressure to grow. And they don't.

Even with that, consider the size, construction, intention, and fragility of the root structures that are the leading edge of the attack (if the illustration shows up). These explorers are very tiny indeed to exploit the available pore spaces to have room to grow. They have a root cap which functions as an armor and as a lubricant. And they are pushed by the expanding piston engine of the apical meristem.

While I was typing this, one of those insipid gardening shows wandered on the TV with its host chattering away about drainage or something and the camera panned across a very clayey soil with a profusion of tree roots growing across the surface. The roots aren't there by choice; the heavy clay soil beneath forces them above ground and they are really on their way somewhere else.

The roots through the foundation wall you saw are exactly that, on their way somewhere else and the basement wasn't it. Ooops! They didn't make the hole or crack, they found it--or at least the initial tiny root tip came across it. Cracks in foundations and brickwork are lines of cleavage. Diamonds are the "hardest" substance known, but they cleave quite readily--for someone who knows the tricks.

The mechanics of a foundation crack generally include the weight of the house resting on it and a relative lack of support or a change of support beneath the footing. Root pressures aren't in that league. A root coming through a wall was simply taking advantage of the space being there; it didn't create it. The accused is innocent.

A displaced or bowing basement wall can be a result of increased adjacent pressures from a tree, I guess, but I've not ever seen that. An inadequately engineered or constructed wall can deflect without a nearby tree and the science of soil pressures and wetted soils is better explained by someone else. Foundation walls are retaining walls holding soil back out of an empty space;the basement. This function is aided by the weight of the house on the wall. Most of the weight of a tree is carried straight down, the soil type can have a lateral force capacity but it is site specific and I couldn't generalize about it.

I try to be careful about assuming something nearby being "the cause." That's the step just before "knowing its the cause" and discarding other possibilities. Crank that up on the urban myth machine and you see the proliferation of questions to these forums by people concerned about trees as a threat to buildings. It's big business in the UK and I don't hear any loud counter-voices as an offset.

Your skepticism is healthy and I have an obligation to explain my positions clearly, but I think a little common sense examination of the particulars will help dissolve the new clichés. I don't want to argue angels dancing of the head on a pin or play semantic tricks; I am an incorrigible pragmatist and will drop a theory in a second when given a practical example that counters it. But I will then also subject the practical to the same tests to see if there are alternative explanations.

The question is not whether trees can constitute any threat at all, the question is have we amplified the problem beyond its true presence and mistakenly chosen the felling of trees as our preferred solution?


Bob Wulkowicz

Reply to post by Bob Wulkowicz, on August 09, 2001 at 19:43:42:

Bob, you pointed out that roots may be "on their way somewhere else" in some cases. This is how a wall can be damaged.

The root tip will find its way into a tiny crack or crevice. It may be turned aside, yet still survive. The root tip that survives expands into a root, which grows laterally. This root then exerts a lateral pressure on the objects adjacent.

In most cases of damaged walls, curbs, etc. that I've inspected, the structure was defective in some way. It had cracks or crevices for the roots to enter. This also implies a weakness at that point. So regardless of the compress or tension ratings of the concrete or other material, the structure's ability to withstand pressure at the defective point is less.

Roots can and do exert pressure. Mattheck estimated a possible pressure of over one mega-pascal (one million newtons per square meter). Now obviously, the root is pressing over a smaller area, but it's still a lot of force. Combined with other forces such as freeze/thaw cycles, slight shifting of the roots or soil due to tree movement, shrink/swell of the soil, etc., a wall with a weakness can be damaged. It may not be the tree that caused it, but it certainly can contribute to the problem.

In Mike's case, the foundation wall is probably new enough and well enough constructed that there will not be a problem. Old foundations with crumbling mortar would be an entirely different story, however.

Reply to post by Russ Carlson, on August 24, 2001 at 22:24:48:



"In all things it is a good idea to hang a question mark now and then on the things we have taken for granted." Bertrand Russell

______________


Bob, you pointed out that roots may be "on their way somewhere else" in some cases.

This is how a wall can be damaged The root tip will find its way into a tiny crack or crevice. It may be turned aside, yet still survive. The root tip that survives expands into a root, which grows laterally.

__________________

Russ,

Roots are notoriously on their way somewhere else. That is what accounts for root-bound plants in pots and girdling roots on trees. Roots search, explore, and exploit; indeed, it is a critical function of what they must do. Once past the buttress area where root sections serve a structural purpose, roots sick to the business of being the water and mineral transport mechanisms.

Encountering an obstacle is an everyday occurrence for roots and so wrestling for survival at an obstruction is rarely a consequence. When the path for an root apical meristem is blocked, the meristematic tissue further back simply creates a new apical point (obviously at right angle initially) and begins to grow in that direction. It is a wonderfully simple adaptive mechanism that works quite well. The root doesn't waste its time fighting, it goes somewhere else as a new lateral root.

__________________

This root then exerts a lateral pressure on the objects adjacent In most cases of damaged walls, curbs, etc. that I've inspected, the structure was defective in some way. It had cracks or crevices for the roots to enter.

This also implies a weakness at that point. So regardless of the compress or tension ratings of the concrete or other material, the structure's ability to withstand pressure at the defective point is less Roots can and do exert pressure.


____________________

I agree that the radial growth of roots creates a pressure, but again it is not in a range that can threaten concrete--even concrete weakened by other conditions. I also can't agree with your statement that compression or tension ratings adjacent to a crack or hole are somehow less at that defective point. The general integrity of the wall may change to some degree, but the strength of the surrounding concrete is essentially unaltered.


Mattheck estimated a possible pressure of over one mega-pascal (one million newtons per square meter). Now obviously, the root is pressing over a smaller area, but it's still a lot of force. Combined with other forces such as freeze/thaw cycles, slight shifting of the roots or soil due to tree movement, shrink/swell of the soil, etc., a wall with a weakness can be damaged.

You are aware that I am very troubled by many of Mattheck's pronouncements and the interpretations attributed to him. If I look in my conversion tables, the megapascal pressure you quote translates into 145 psi (1MPa). The water pressure from my pump at the cabin and at most city faucets is about 45 psi. This is not a big time pressure.

If I tripled the water pressure on my pump and held a garden hose nozzle against my foundation wall, does anyone think I would push a hole through the wall? I might blow a hole in the hose, but not the pump, the fittings, the nozzle or the concrete. That pressure attributed to the growing tips of roots is nowhere near the pressure necessary to affect concrete.

What is needed? Here's a typical rule of thumb today for cutting concrete: we find "a ratio of 3.5 psi. water pressure for every 1 psi. compressive strength of concrete is used to calculate optimal operation pressure. If a concrete core test indicated nominal compressive strength of the concrete to be 5,000 psi., a minimum water pressure of 17,500 psi. is indicated. "

This is what I mean about throwing the theoretical away in a second when presented a practical consideration. A strength of 5000 psi is pretty close to residential foundation strengths and the 145 psi pressure from the tip of a root ain't beans to those walls.

The photo at the top of this piece is of a tree root showing the cap, the meristem, and the elongation zone. If you can see and count the cells, the structure is obviously microscopic. The force claimed for it are available only at its microscopic tip. This size is what enables it to slide through pore spaces and if it encounters a concrete wall, this is the area of pressure exerted against that wall.

Even if 100,000 root tips arrived at the wall at the same time, would they penetrate the wall? How many angels can dance on the head of a pin?.


________________________


Now, let's consider a lateral pressure as you suggest from roots growing horizontally and parallel in relation to a wall:

In a study sent to me, the authors attempted a compilation of papers on tree root pressures. I don't have it in front of me, but I remember a quoted primary growth forward pressure of 128 psi. The authors couldn't find a lateral growth pressure (secondary growth) anywhere, so they assumed a lateral pressure of at least the same 128 psi. The need to have both pri. and sec. answers for their paper prompts them to assume a number just to fill in the blank(?)! I don't find this great science, and I certainly don't find it a benchmark for pressures from diameter increases in roots adjacent to walls.

But let's use the Mattheck 145 psi. Even if it were true, this is even less likely a meaningful factor in distressing foundation walls. Our roots will probably exist mostly in the approximate 18" root zone that they occupy everywhere else. And even if they were laying right next to the wall, they would first compress the adjacent soil until it was incompressible before they would exert any subsequent pressure on the wall. The contact point of the root circle to the contact point of the next root circle against the wall will be determined by the root's diameters as an "automatic" spacing depending on root age that reduces the potential pressures..

I have only seen vertical and diagonal cracks in foundation walls, which would be consistent with vertical displacement and settlement. I have never seen horizontal fractures or cracks that would imply lateral pressure from lengths of pressure increasing structures like roots.

And if these roots went under a foundation and tried to lift it based on a 145 psi capacity, we're expecting a living expanding cylinder using its ability to divide cells to raise a foundation wall, the floor loads, the building contents, the framing, the roof timbers and the shingles? What pressure would that take? But more importantly, would the cells stay alive at that pressure to continue their division, expansion and subsequent growth.

I can crush the cells of a root or branch with a pair of pliers. I can impede radial growth in a woody cylinder with remarkably small counter pressures. I have hundreds of photographs illustrating the reluctance of meristematic cells to kill themselves in any kind of expansion that hardly approaches the pressures needed to lift a foundation and its vertical loads.


________________

It may not be the tree that caused it, but it certainly can contribute to the problem. In Mike's case, the foundation wall is probably new enough and well enough constructed that there will not be a problem. Old foundations with crumbling mortar would be an entirely different story, however.

________________


Trees really don't cause the problems--and in my judgment, don't really contribute either. A mega anything sounds big. The explanations seem plausible until they're examined more closely. Our prejudices and ignorance do not change the laws of physics or biology. Our deadly inclination to repeat myths and clichés will condemn more trees.

I keep sputtering. Please tell me where I'm wrong.


Bob Wulkowicz

Reply to post by Bob Wulkowicz, on August 26, 2001 at 00:02:18:


I'm pleased to announce that the pig-headed bulldog Wulkowicz (how's that for a mixed anthroporphical metaphor?) has found the probable fatal flaw in the root pressure debates.

Claus, hold onto your socks...

Allow me a while and counsel me where I should publish.


Bob, A rumplestilskin-like Yank on a bank in beautiful costal Nove Scotia.

Reply to post by Wulkowicz, on August 27, 2001 at 22:34:31:


OK, OK.

I weren't as smart as I thought I were.

SeemsI left out the "mo" in anthropomorphical.

As I have often said, that stupid word is longer than it has any right to be.

But, I still have the answer to the "we agree to disagree" crowd about roots.


Bob

Smug as a bug in a hug with Bella Abzug