We have just moved to a new home that has two fifty-foot eucalyptus trees in
the back yard about 20 feet from the house. The area where the trees are is
plain dirt that has never been planted/irrigated. The tree roots do not
appear above ground.

We'd like to pour concrete in the back yard area to make a patio. Any
suggestions on what to do or not do when laying out the concrete forms such
as minimum distance to the trunks?

The trees have been here a long time and we don't want to do anything that
will injure them. This is in Los Angeles.

Thanks.