I am contemplating building an addition to my house. It will consist of 2 rooms, 20X20 and 15×20. Since it will be built very near a beautiful 50ft tall maple, I want to be careful not to ruin the tree roots.
Here is my question: what do you think about using piers instead of a continuos foundation. Is it less likely to harm the tree? Is it an acceptable method otherwise? I live in new jersey and I don’t think frost heaves will be a big problem.
Thank you for any advice you can give.
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Replies
I'm building in a heavily wooded site myself and learned the hard way regarding having big excavation equipment up close to mature trees. Two white oaks dead so far, but unavoidable 'cause the water line had to go there. I'm worried about several more red oaks that have had the soil around thier roots disturbed and compacted by excavation and backfill equipment. Also assorted dings to thier bark.
I'd have a tree or forestry expert come around and take a look. I did that way too late in the game, and actually could have saved alot of time, money, and frustration if I had cut down a few more trees that will die anyway.
Some municipalities and/or counties have these people around.
Is this rural or city?
Meanwhile, remember that most trees get thier nourishment from feeder roots that are very close to grade level...within the first foot or two, and approximately within the drip line from the branches above.
We built a cabin in the woods on pier and beam, dug the holes by hand. (Now that was minimum impact but alt of work) This is was six years ago right next to a double white oak...the deck comes to within 8 " of the trunk...and that tree is still very healthy. I actually cut a root or two on this one as the hole was being dug, and white oaks are among the most sensitive to root damage.
What I'm getting at is that with a full, excavated foundation...which we've just been through while adding a major addition to the cabin...it's not just potential damage to the tree's root system from the foundation trench itself, but also the collateral damage from compaction and root area disturbance from heavy equipment that needs lots of room to manuever and backfill, lots of piles of dirt around, that is almost as big a concern.
If you do piers, even if you bring in a machine to dig the holes, you will end up with 1/10 the direct and indirect damage to the tree.
Still, if you really want to save the maple, you should get a tree guy over there soon, as you may want to change your design for less impact.
Good luck.
Edited 10/22/2003 11:43:40 AM ET by johnnyd
thanks for the reply. this is a suburban lot with a busy road in the from and a beautiful 200x600 forest in the rear. Thats why I value the tree so much. I feel like I'm far from everything with only a 15 minute commute.
Since I know very little about trees, can you tell me about the drip line? I assume it would be around the perimeter of the tree canopy. If so the question I have is, can this be covered? Even if the piers manage to avoid most of the roots, If no water falls where the roots need it, could it also damage the tree. It sounds like I do need to consult an expert, but any help you can give would be appreciated.
You need to do everything you can to protect the tree's current environment...from the base of the trunk out to the drip line...which is where the outer-most leaves and branches shed water. Any compaction or addition of fill in that area will hurt the tree.
How close to the drip line is your planned addition?
the question is not how close to the drip line, but how close to the trunk. my planned addition was to be within 10 feet of the trunk, with 60% of the addition being under the tree canopy. I am already rethinking this in my head. The tree side is the only side where I can expand, but I may be able to keep it near the canopy edge or decide not to add on at all.
This forum is very helpful, as many of the topics coming up are things I hadn't even considered.
Yes, THE most professional and fun construction forum I've seen. Lots of activity, too.
To bad it's so hard to duplicate the charm of a large tree growing right next to an attractive house. Usually they grow there AFTER excavation and construction, so it's not something that's quick to accomplish.
I wouldn't give up on the idea of pier and beam, if done correctly it will be plenty strong and stabile and would definately minimize tree damage, but still get an aborist's opinion.
Good luck.
The only way I'd build a climate-controlled building on piers is if I could have ready access under it. It's difficult to make the floor breathable and varmint-proof.
Here's a pic that shows how tree roots actually grow. Can't remember where I got it from.
View ImageI don't care about crime, I just want to get the guns. [Senator Howard Metzenbaum]
Actually, tree roots grow in the direction where they find water. Plant one in the middle of a lawn that is lightly watered very frequently, and you'll get the shallow surface roots of the second picture. Dig a nice big basin around the tree and flood it regularly, and you can get the roots to go a bit deeper. But you also have to consider what's down there, like is there an impermeable clay layer?
A lot of the trees in this city get into the shallow surface root syndrome, and every fall the Santa Ana winds and the rainstorms knock bunches of them over. They act less like a plant growing in the ground than like a floor lamp with a heavy base.
As for building close to a tree, bad idea. Bad for the tree, and also bad for the roof and gutters of the building. Clogging, flooding, constant dampness, moss and mold, dryrot and termites.... Also consider that if you put the house far enough from the tree, you might be able to look out a window and see it.
-- J.S.
Hey, Jerome.
I'm one of those pesky insurance guys. You might need to check with your agent. Here in Georgia we require a solid masonry foundation, unless it's a porch or a deck. Piers might backfire on you later.
Greg.
Thanks for that advice. I know piers are ok with code, but I will call my agent also.
Some local codes/bylaws do not allow pier or post foundations. Generally, they are difficult to weatherize.
As the previous poster said, the important active roots are relatively shallow, and near the drip edge of the canopy.
I have read that even a big tree can be 'trained' to produce new feeder roots closer to the trunk by cutting back the canopy in stages, and pruning the roots to match. If this were done in advance of construction, and the drip edge were moved back past the excavation line, your tree might have a better chance.
I have tried this cutback technique with smaller trees and shrubs prior to transplanting with some success. Never tried it on a big tree.
Based upon observations, maples are more fragile than many other trees. Repaving in our area lays waste to the maple street trees. I lost a massive and previously healthy old maple on my property after street was paved. I was lucky though. 3 others fell on houses in my neighborhood! Each of these trees lost about 1/3 of their roots during paving. Some survived, though the branches on the street side generally died because they lost their corresponding food supply. Maples seem to be worse at healing wounds than many other trees as well.
At least the oaks have a big tap root, so they are more likely to stay standing long enough to heal.
thanks for the info. I had said I was dealing with an oak, but it is in fact a maple. Sounds like I can't be too careful here.
Maples are notoriously shallow-rooted. That's why there is seldom much undergrowth in a maple woods. Thus, they are more susceptible to root damage from surface activity.
I did an addition next to a giant elm tree and we dug piers by hand and created a2' tall crawl space. I ran 5" angle iron all the way around set it on the footings for the piers and laid brick on top of the angle iron. This did a fair job of not cutting all the roots but I still had to dig 2' x 2' holes every 4' so that did not leave much undisturbed ground. Definately call in an arborist to give you suggestions on saving the trees. One thing they suggested was to put down a thick layer of mulch every wear trucks or even lots of foot traffic are going to occur.
ANDYSZ2
I MAY DISAGREE WITH WHAT YOUR SAYING BUT I WILL DEFEND TO THE DEATH YOUR RIGHT TO SAY IT.
thanks for the advice. the way you did the bring sounds interesting also. I don't like the look of pier alone
Check out this publication:
http://www.umass.edu/bmatwt/publications/articles/preserving_trees_during_construction.html
When you say the tree is "very near" the additions, that concerns me. Are you sure you want the tree there when it's 90' high and dies?
Ya gotta plan for the future, not just how the tree is now.
When I'm waiting in line or brushing my teeth, I'll contract my butt muscles [Heidi Klum]
good point. the tree is already at least 50' high and wide. I love the tree, and would rather replan my addition that risk killing the tree. as regards how close I am, my current plans puts me within 10' of the tree. Since my lot is only 50' wide any building I do will have to be fairly close to the tree.