Home Addition Dangerously Close #167810 - Ask Extension

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Home Addition Dangerously Close #167810

Asked February 23, 2014, 4:21 PM EST

We are planning an addition to our home that with come within 6-8 feet of 3 lovely mature trees that we don't want to loose. We must dig a foundation and disturb some roots. What are the chances we will loose them if we do this? How can we help the trees through this process? Who has knowledge about this and could help us?

Larimer County Colorado

Expert Response

Thanks for your question. Yes, you have a right to be concerned, as tree roots extend 3-5 times the width of the canopy and tend to be very shallow (most roots are in the top 12" of the soil profile).

Fortunately, there's a lot of great information on protecting trees from construction damage. It appears as though the work may have started? Or at least materials have been delivered. Now is the time to ensure that your trees are protected as best you can. The tree species will also be a factor. It looks like the trees are a type of evergreen...maybe pines? According to the chart from CSU Extension, pines have a moderate tolerance to construction damage. 

The University of Minnesota has an extensive website on this subject: http://www.extension.umn.edu/garden/yard-garden/trees-shrubs/protecting-trees-from-construction-damage/

The section on "plan ahead" is one you should refer to. Be aware of where equipment will drive, where supplies will be dropped, etc.

For your trees, especially the ones you want to save, you need to establish a "Protected Root Zone" (PRZ). In general, the PRZ is going to be the entire area below the tree, extending to the drip line of where the canopy extends.  

Yes, any damage to the tree...trenching, soil compaction, etc. can result in potentially harmful consequences. After construction, you will need to carefully monitor those trees. If the root system was severed with equipment, those trees may become unstable. A certified arborist can help assess the health of the trees and determine the action you can take to keep them healthy. Regular water is going to be very important. Again, all of this is covered in the website linked above.

CSU Extension also has some great information: http://www.ext.colostate.edu/pubs/garden/07420.html
Alison O'Connor Replied February 24, 2014, 11:47 AM EST

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