[CANUFNET] Sidewalks and trees

[Julian Dunster]

I am looking for design specifications that enable sidewalks to be built 
close to trees and over roots.

Currently the most commonly used requirement in Canada and the US seems 
to be a 4 inch thick concrete slab on top of compacted gravel that is at 
least 4 inches deep. That often means an 8 inch minimum excavation with 
associated root damage.

We have access to a product called Combigrid which is a geotextile 
fabric bonded to a biaxial geogrid. Ideally I would like to be able to 
lay this onto the native soil (rake off or scrape off top inch or so of 
loose materials) and then pour the slab straight onto that, possibly 
with mesh reinforcing in the slab. The engineers have rejected that 
approach and want compacted sub grade on top of the Combigrid.

The sidewalks seldom have to be rated to H20 
(https://bandt-us.com/h-20-load-rating/#:~:text=H%2D20%20refers%20to%20a,16%2C000%20lbs%20per%20wheel%20load.) 
so in theory the design should be quite simple but in practice isn't.

I would appreciate links to or specifications for alternative ways to 
create sidewalks that do not involve deep excavation into the root zones.

AND

- no, moving the sidewalks is seldom possible

- thinner slabs not accepted

- only concrete to be used.

- I need an affordable design that can be used regularly as this is not 
a one off situation - it is a routine problem that I am trying to solve.

jd

-- 
Yours sincerely,

On Behalf of Dunster and Associates Environmental Consultants Ltd.

  

  

Dr. Julian A Dunster R.P.F., R.P.P.., M.C.I.P., ISA Certified Arborist,
ASCA Registered Consulting Arborist # 378,
ISA Tree Risk Assessment Qualified
Honourary Life Member ISA + PNWISA

www.dunster.ca		www.treelaw.info		North American distributor for Rinntech www.rinntech.info