Foundation Install with Interfering Surface Roots

[Hexa Fox]

Hey guys,

I have this ongoing project and I was hoping a knowledgeable arborist or at least someone knowledgeable with trees could advise me. I would really appreciate any feedback. So long story short, I have a large shed 12x16 on my property that is also pretty tall with a loft area. The problem with it is that it was installed and leveled on cinder blocks. Overtime the band boards on the building have started to splay out from under it and I need to get it addressed as soon as possible. Anyway, my plan is to just have a company move the building to another location on my property.

This has been stressing me out for awhile now because I need one company to lay the foundation and another to move it. Finally I have found a company to install a gravel pad as the foundation that has excellent reviews and they are going to compact it and add a wooden retaining wall around it. The problem that I am facing now is that there is a very large Silver Maple tree near where I wish the shed to go. I had a proposed location on my property marked off yesterday for where they will place the foundation. There are several surface roots from this tree in this area. The company said removing the surface roots would not be a problem and they do it all the time without problems. I know that removing surface roots can be problematic for trees though. The rep also said that this area would need to be dug out between about 4"-15" to make it level and make room for the gravel. So they are going to be going down a considerable amount on these surface roots and I have no clue how much more could be down there.

I also took a few pictures that I know may not do a whole lot but hoping it will help give you guys an idea of what I am dealing with. I also really do not want to remove the tree at this time but I sure do not want to kill it and it fall on top of the shed. That would be a disaster. There are definitely larger surface roots around this area but they are not directly inside of the location. I tried to bias the proposed location away from them. I also plan to try to have either 4x4's or 6x6's laid between the gravel bed and the shed frame and be able to anchor them somehow. Again I appreciate any feedback from you guys!

 

[Bullseye T&L]

There's a big difference between 4" and 15" when you're talking excavation and root removal. At 4" you might could get away with making a clean cut 4" down along perimeter then excavating. If you're going 15", then making a pruning line is going to be more difficult, and you may want to treat the tree with a growth regulator prior to excavation - which in human terms is like putting it to sleep before surgery. So a good soil sample first would help to know whether they need 4" or 15". They need solid ground to build up from, so I get the depth range.

I would take this up with them and see if they can give you a more exact depth prior to excavation. If not, then call a local arborist who does this kind of thing. Two points are 1) clean cut those roots along perimeter before excavating, and 2) don't excavate deep unless tree is in dormant state. I wouldn't try to bulldog a maple, at least down here in zone 7b/8a. Not sure what zone you're in.

 

[Hexa Fox]

There's a big difference between 4" and 15" when you're talking excavation and root removal. At 4" you might could get away with making a clean cut 4" down along perimeter then excavating. If you're going 15", then making a pruning line is going to be more difficult, and you may want to treat the tree with a growth regulator prior to excavation - which in human terms is like putting it to sleep before surgery. So a good soil sample first would help to know whether they need 4" or 15". They need solid ground to build up from, so I get the depth range.

I would take this up with them and see if they can give you a more exact depth prior to excavation. If not, then call a local arborist who does this kind of thing. Two points are 1) clean cut those roots along perimeter before excavating, and 2) don't excavate deep unless tree is in dormant state. I wouldn't try to bulldog a maple, at least down here in zone 7b/8a. Not sure what zone you're in.

Hey Bullseye,

Thanks for the advice. I was actually just reading another thread where you recommended something similar. So I want to make certain you understand, the reasoning for the difference in depth in my case is because of the grade. The rep said that the front right flag was the lowest and they would only need about 4" there but the back left flag was about 15" difference. So quite a bit. The roots are more toward the middle but on the left side. So they may be closer to 10" or something. I should have asked them to take a depth measurement there to see how much would need removed near the surface roots. I live in West Virginia so everything is on at least a slight incline lol. My zip code is 25414 if that helps you.

So you think I should try to find the roots or request the company find them right where they come into interference with the foundation and terminate them?

 

[Bullseye T&L]

You're zone 7a, so that is close to the temp range I live in.

So you think I should try to find the roots or request the company find them right where they come into interference with the foundation and terminate them?

Yes, that is good practice. But it becomes more critical the closer you get to the tree, and the more roots you are going to excavate. Think of roots like canopy. If a wind came along and broke off few small branches, you might could ignore the broken tips and nothing may ever come of it. But if that wind ripped off large branches and left large areas of damage on major limbs, the tree could end up with major problems on down the line, and it would be wise to get a climber up there to trim the limbs back to good termination points.

You know, at 15" though, there is DIY option you could do. Once they mark the excavation area, you could do the root pruning yourself. A heavy duty reciprocating saw (read corded) with some longer blades could be used. I do this when I'm putting in retaining walls and have to excavate a trench for blocks in the vicinity of a large tree. Now I rarely go past about 6" deep, but there are some longer saw blades out there that could work for you. Just buy a bunch and be ready to toss them when they quit cutting. It will be work for sure, but you should be able to knock it out in a few hours.

The problem if you don't root prune first, or if you disturb the roots too much while tree is not dormant, is that the tree could start dying back on that side. Even if you do everything right, you still could have it do the same because you still removing roots. But the odds of having a problem are higher by not root pruning first. If it does die back, then you're looking at hiring a climber to come get a bunch of dead limbs from over your shed which will be costly for a maple that size. The root pruning is definitely cheap insurance.

 

[Bullseye T&L]

Oh, and right now is a good time to root prune, even if you don't plan on having the work done until later.

 

[Bullseye T&L]

The roots are more toward the middle but on the left side. So they may be closer to 10" or something. I should have asked them to take a depth measurement there to see how much would need removed near the surface roots.

I just wanted to comment on this to clear up up any possible confusion. There are roots under the entire marked area of the new pad. The surface roots are just the ones you can see, and are not necessarily the largest ones you'll run across when root pruning. There are plenty under the entire pad. And with silver maple, they tend to be shallow, so you will be excavating more root zone than some trees that have deeper root systems. And lastly, roots will tend to stay in the upper zone even as grade changes, so digging deeper in that rear corner will excavate more root zone, though the roots there will be smaller.

 

[diver64]

If you dig 15 in outside the drip edge of the canopy I don't think you will have a problem with the tree

 

[Hexa Fox]

Hey Bullseye,

Thank you very much for the replies. I sent this same information back to the company that will be doing the foundation and they forwarded it to the guy that is going to be doing the excavation. They got back to me this morning and said that they would like to excavate around those surface roots as best as possible, then lay and compact the gravel.

Does this make a lot of sense? Because if they lay and compact the gravel around the surface roots can it survive? I do not understand trees all that much, but could these roots become a problem? Like if not terminated what are the chances of them rising further to say find moisture and ending up inside my shed lol?

I actually just bought an M18 Sawzaw on sale this year and got a huge pack of assortment blades to go with it. So terminated at least some of those roots would be possible.