Cut the roots -- with that much to do, use a ditch witch, as
suggested. Find out how deep the horizontal roots go -- the tree may
have deep roots (I'm not familiar with Ficus roots), but probably the
spreading roots are near the surface.

Then put in a blocker. Vinyl flashing might be adequate; you can get
24" wide for about $1.20/ft at HD, probably less in bulk. Or use the
narrowest ditcher you can, and fill the trench with concrete, but I'm
sure that'll cost a lot more than flashing.


This page

http://www.gardenguides.com/109073-r...cus-roots.html

sort of implies that Ficus roots are shallow, maybe even only 12"
deep. I also found comments somewhere that Ficus produces shallow
roots in AZ because of lawn watering that leaves the surface damp with
no water below, implying that avoiding lawns and using only drip
watering if it's necessary at all might reduce the root problems.

I found a long and very interesting thread about Ficus in AZ at

http://forums.gardenweb.com/forums/l...571812302.html

That thread is five years old but I'll bet a lot of the same posters
are still around.

As to whether it's a water waster, I found differing opinions on how
much water Ficus uses. In any case, one has to balance the water use
with how much it lowers the cost of cooling buildings. Of course in
southern AZ one can use swamp coolers.

I have some great recommendations for shade trees ... for Florida. The
ones I like won't grow in AZ.

Edward