Foundation wall crack due to a tree.

[MtlPeter]

I have a number of opinions as to what is happening with this building. A large maple is in the front of a poured concrete foundation house. It is 10 feet away from the foundation. The tree is about 35 feet high. There is also a similar size blue spruce ?-( trees I don't know -small bluey neddles though).It is at the cornor of the house.

One opinion says the culrit is the maple. That is why the front face of the brick has cracked and why the foundation has cracked on the rear cornor on the opposite side and on a diagonal to the tree. The crack is vertical. There is also a very large tree (>30 feet about 4 feet from the house at the back.)

One opinion says to cut down the front maple and don't worry about the blue spruce.

One less " informed says" whack 'em all." I love old trees and thus am reluctant to do this. The house has been in place for 27 years but there has been some measure of drought the past few years and the opinion says this has caused the trees to pull the water from the heavy clay soil. Thus aggravating the problem.

Thoughts please !

 

[AJUK]

The trees are clearly the problem, both of them will have an effect but you have to gauge the water demand of each species against the shrinkability of the soil. Heavy clays are very sensitive to water content changes, especially if they are overconsolidated (previously loaded with other strata or a glacier etc.). The best suggestion is to obtain the services of a local structural engineer who would be able to assess these issues for you and offer some sound and reliable advice.

In the UK, this is a major problem and well documented. It should be something that is covered by your buildings insurance or even by a third party if the trees are not yours!

With regard to cutting down the trees, you have to ask the question, what is more valuable, your home or a tree? Trees will always grow again, free of charge! However, cutting down the offending tree is not always the solution particularly if the tree pre-dates the building.

Best of luck but post if you have further questions.
Regards

 

[Bbird]

The reported crack is vertical and this is likely to be the evidence that something has come up from the underneath casuing the tension in wall panel.

Maple has large roots but the roots for the spruce are relatively shallow. I hacked my 50ft tall maple that used to be 24 ft from the house and have done quite a few spruces too. Luckily the damage by the trees was confined to the paving and drive only.

You could satisfy yourself by digging up the area between the tree and the house and get to the roots. It is possible to limit the damage by hacking the offending roots and keep the trees. However be warned that a tree, with roots partly severed, may lean to a undersirable position in future.

If it is my house I would have the trees cut down and the stumps removed. Whatever left underneath the foundation will rot but it will take many years to take effect. Even rotten roots can a small load bearing capacity. This is based on my experience of removing tree stumps and finding rotten but intact old roots still inside the soil body.

 

[BigH]

There was a great paper by some guy from Canada years back about trees and damage (Bozozuk???? - I'll try to find proper reference later).

Before you start hacking you trees - and losing many dollars in property value - you might do well to sit down and take a look at the goals you wish to seek (I put in a note to a thread on water in the basement and I'd suggest you read this).

First - is the crack so bad that the wall is potentially going to collapse or kick in? Or is the crack relatively minor and you just don't like it? Is the basement finished and your spouse is ticked that it has ruined her/his great wall-paper job? If the crack is not so bad as to create a structural problem and the basement is unfinished and there is no urgency, why not wait to see about the next season. You've indicated a drought this year so it must be abnormal weather (the water in the basement was abnormal rainfall). Ponder the above questions - before you go off and start hacking down your beautiful trees. Focht3 made a good point of checking with someone in the know about roots and root systems. Sometimes, I think one just has to sit back, smoke a good Havana and ponder the pluses and minuses of action vs inaction. Too many times we try to engineer in situations that don't really need it . . . yet, if ever.

Anyway that's my few Baht worth.

 

[Bbird]

Life has taught me that we always want things we haven't got. Trees are great for those who hasn't got a couple hundreds in his garden, doesn't have to sweep leaves, cones and seeds several times a year, hasn't got drain blocked by the tree roots, hasn't had half a tree body snapped off and landed on the roof during high wing, hasn't had a tree leaning over 60 degrees and continuously every year towards the house etc etc.....

I think a reduction of trees in some cases could do no harm to the property value.

 

[rowe]

Because the crack is vertical, it is likely due to the tree(s). Most settlement cracks propagate diagonally through the mortar joints (like stair steps), often at windows and doorways. But, I agree with BigH. If it is not presently a structural problem, and if you really would miss the trees, wait awhile to see how damage may progress.

It sounds as if the brick you've discussed is similar to a perimeter wall on a nominal foundation that supports the timber sill of the wall framing. If that is the case, some repair is probably necessary, even if you don't see obvious signs. My biggest concern would be moisture intrusion and subsequent rot that may not be readily visible.

Most cracks less than 1/8" are characterized as "hairline" and will likely not permit significant moisture intrusion (bricks are porous - and some moisture will pass through anyway). Adequate repair does not include silicone. A proper repair will require removal of the damaged mortar and brick (if the brick unit is damaged), and replacing the with the appropriate mortar mix (repointing).

There is a local residence (timber with board siding) that is well over 100 years old. The structure is fairly well known in the county - because there is a HUGH oak tree that has continued to grow thru the wide porch and roof. From the owners point of view, the tree is too beautiful to remove and keeping the structure sound in the vicinity of the tree is considered maintenance, which it does require at two to three year intervals. That does not mean that your trees will require that much maintenance, but it all depends on what you're willing to put up with to keep the trees.

 

[BigH]

Bbird-you might be surprised. Check with a real estate agent. I've heard of property values dropping nearly $10k because a couple of trees were cut. Of course, if you are out in farm country, you might be right.

 

[sinkholeorg]

We had the same problem working on what was called a "sinkhole" underneath the structure by a geotechnical investigation. The house had 1/2" stairstep cracks on either side of the NW corner. Once the problem was "correctly" diagnosed as a previous water leak (unchecked for two weeks) where a large water oak has absorbed more water than usual and caused the roots to swell underneath the corner. An arborist was called in to surgically cut the the affecting roots (less than 10% of the total root system). The process took two days, the tree was saved and problem corrected. Two steel piers were installed to realign the corner and prevent settlement from future organic decomposition.

 

[PSlem]

I worked on a house with a large oak (about 4' trunk) breaking the crawl space wall. The tree was a major feature of the property and the joists ran perpendicular to the wall in question, so we built a new wall 5' back and left the tree. You don't necessarily have to move the whole wall, just a portion, and of course, check the loads and strengths.

 

[umgrego2]

I agree with ajuk and bigh.

Where I live, we have a high clay content in the soil. It has become common knowledge, even amongst non-engineers, that you avoid at all costs cutting down a tree that close to the foundation.

Property value will also go down considerably if there are few trees on the property to begin with.

I say hire yourself an experienced foundation engineer, can be tough to find sometimes, and get their opinion.

 

[Focht3]

I've looked at a lot of residential foundation failures, many of which were (incorrectly) blamed on trees. You need to be systematic in evaluating the problem. Here are some of the possible causes of foundation distress:[ol][li]Large trees[li]Leaking sanitary sewer lines[li]Leaking water supply lines[li]Unstable slope[li]Construction defect[li]Design defect[li]Poor drainage[li]Seasonal weather changes[li]Extreme weather event[li]Poorly conceived addition to the structure[li]Poor lawn maintenance[/ol]I tend to discount all of the potential causes except 1, 2, 3 and 4 - the house has had plenty of time for the other causes to occur, but apparently they have not, so it is unlikely due to these.

I'd have the plumbing checked thoroughly before I touched those trees...

AND have a an elevation survey done of the interior of your home. Reference it to a truly stable benchmark. Not only will the existing pattern of deformation of the slab be of benefit, it will also be of tremendous use if you make changes and they don't fix the problem...



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