[CANUFNET] Constructing Driveways within Critical Root Zones

[james urban]

The system I have used successfully for many project is as follows.  Apply  a sheet of geogrid (example Miragrid 2XT) over existing grade, remove any turf or mulch first.  Put about 6"-8” of crushed stone with no fines (example US ASSHTO #57 size stone) then a sheet of filter cloth (example Mirifi 180N).  The build what ever you want on top as the drive way.  Note: no existing soil disturbance and adjust driveway grades as required.  This makes a bit of a hump in the drive way but a good designer can make it a visual asset and blended grades with the right grading approach.  

Read Part 2 Chapter 4 in Up by Roots.

Jim Urban, FASLA

> On Jul 10, 2020, at 11:15 AM, Astrid Nielsen via CANUFNET <canufnet at list.web.net> wrote:
> 
> Hello Canufnet members,
> 
> I have a client that is building two homes on an infill lot where there is a very large (106 cm), healthy silver maple. He is very willing to explore different options for working around the tree that would cause minimum disruption to the roots. 
> 
> Does anyone have examples of building driveways within the critical root zones of large trees that have managed to prevent significant root damage and tree decline? Specifically, he is considering a type of elevated driveway that would not require the severing of roots or significant soil compaction, and dissipate the pressure through posts. Although the posts would cause some root damage, it would be significantly less than excavation for a standard driveway. If anyone has examples of this type of engineering, I would be grateful if you could share it with me.
> 
> Thank you,
> 
> Astrid
> 
> ______________________________________
> Astrid Nielsen, MFC
> Ontario Registered Professional Forester
> ISA Certified Arborist®
> ISA Tree Risk Assessment Qualified
> 
> astrid.nielsen at dendronforestry.ca <mailto:astrid.nielsen at dendronforestry.ca>
> +1.613.805.WOOD (9663)
> 
> www.dendronforestry <http://www.dendronforestry.ca/> 

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