"peter" wrote in message
news:6m7Md.1361$uc.168@trnddc05...
There is a 80-ft tall douglas fir tree three feet from my outside wall and
it has been there ever since the house was built some 20 years ago. I
recently read that roots of large tree could damage house foundation.
However, nobody else (including an arborist, a house inspector) who saw
that tree ever mentioned anything like that, although I didn't
specifically ask them about this issue.

On the other hand, my driveway was cracked by a much smaller tree (maple)
which forced me to cut it down. So "large tree roots may damage house
foundation" does have a ring of truth. On the third hand, if that was
true, the builder (and a reputable one) wouldn't have built the house 3
feet away from that tree, would they?

Arborists if not carefully chosen are just tree cutters, and may
overemphasize "dangers" of tree and roots in order to get a job.
House inspectors, the lowest of the low, often don't catch everything, and
there is no red flag here.
Even reputable builders often leave trees too close to houses in order to
make the house attractive and landscaped to sell. They tend to know little
about trees, but rather building and selling.

Dont sweat the foundation risk unless you see a hint of damage. If curious,
you can dig a test trench along your fdn to see size and orientation of
roots. Roots of practically all trees tend to look for moisture,and back off
from foundations, as under the house it is usually dry.
The biggest risk for your house is limbs falling on roof and invading
sewer/drainage lines, if they are the jointed metal or tile type. PVC with
glued joints tends to resist root damage.

BTW redwoods have no tap roots, as one poster suggested. Nearly all trees
have shallow roots. Here is a quote from the Dept. of Energy:
"Redwoods have the same kind of root system as any other tree. Usually,
the root systems of the redwoods stay close to the soil surface, only going
4-6 feet deep but spreading way beyond the tree, 250 feet in width. " Same
general principles apply to firs.
I have 60-85 foot Monterey Pines that have similar growth styles but smaller
than Douglas Firs, and they are within 18-25 feet of fdn. Perhaps three
feet is a bit close, but as said, I would just monitor fdn, and do test
trench to get root location/orientation. I have also used a bladed punch
bar to chop roots that are going the wrong way, or under driveways.. No real
harm to tree or its stability.