[CANUFNET] Constructing Driveways within Critical Root Zones

[Ian Wilson]

Not a driveway example but I have an example of construction of a new sidewalk across a critical root zone.

Approx. 12 years ago we installed the “Rubber Sidewalks” product in Kelowna, BC. There was a new sidewalk being installed next to a boulevard of mature green ash trees. There was no existing sidewalk, just lawn. We got the construction crew to only remove minimal turf and organics from the surface and avoid cutting any roots. The grade was built up (and tied in to an older concrete sidewalk with gentle ramps).  The large rubber panels were placed over a bed of sand. The sidewalk is still looking good today and the trees are healthy. There has been a bit of mild bending of the rubber panels due to roots but no tripping issues, and small snow plows drive across the surface in winter.

If we did this over again, I think I would have used a coarse structural gravel underneath the rubber sidewalk (no fines). Basically a structural soil but no added compost – to help discourage root growth directly under the panels.

Ian Wilson
City of Kelowna

From: CANUFNET <canufnet-bounces at list.web.net> On Behalf Of Mark Carroll via CANUFNET
Sent: July 13, 2020 12:04 PM
To: Canadian Urban Forest Network <canufnet at list.web.net>
Cc: Mark Carroll <environment1st at rogers.com>
Subject: Re: [CANUFNET] Constructing Driveways within Critical Root Zones

CAUTION: External email - Check before you click!

I don't have an example of a driveway being elevated, but there are examples in the City of Toronto where the house was built this way. The addition was built on stilts to preserve the roots. A full concrete pad was elevated and the addition was built on top. It is not uncommon for this to be done. England has made some good practices for preserving their trees. They have actually built basements under the roots of trees. There are engineered peers that can be drilled down to the 2.5 to 3 meter depth that will support the needs of a carrying load to build a driveway and keep the root zones intact.
Mark Carroll
ISA Certified Arborist, Qualified Arborist Tech
All around nice guy
Taking our environment first
Thanks for connecting...

On Fri., 10 Jul. 2020 at 11:26 a.m., Astrid Nielsen via CANUFNET
<canufnet at list.web.net<mailto: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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