A. When you see the damage that a tree’s surface roots can do to a
sidewalk, it may seem reasonable to infer they could damage a
building’s foundation in a similar fashion. However, most tree
roots are found in the top 6 – 18 inches of soil where there is a
favorable balance of moisture, oxygen and nutrients. While roots can
damage a relatively thin layer of pavement overlying the soil as
they grow, most foundations in western Pennsylvania are much deeper.
The surrounding soil at such depths stays too wet for too long a
time to support much root growth. And many homes have eaves that
keep the soil right near the foundation dry year round, another
situation that is not conducive to root growth.
Trees close to foundations cause concern as
trunks and roots expand over the years
It is true that
the change in soil moisture near a foundation is the most damaging,
especially in times of severe drought such as we experienced in
1988. Fortunately, it is rare that we experience such severe drought
conditions in western Pennsylvania. And as much as gardeners
complain about our clay soil, it's much more stable for building
foundations than sand is. Trees and shrubs planted near a foundation
can compound the situation because they will take up any available
moisture during such major drought events. When the soil around a
foundation dries out completely, it shrinks away from it and makes
the foundation less stable.
When planting trees near your house, it best to plant them away from
the house at a distance slightly greater than the expected crown
radius at maturity. This not only keeps the majority of roots away
from the foundation, but also keeps branches from damaging the
siding or roof as they move in the wind.
Of course, you will need to do a little research on that cute little
treasure you just bought at the nursery if you are unsure of its
mature size. Better yet, do your research BEFORE you visit your
local nursery so you do not wind up falling in love with a tree that
you do not have room to accommodate when it is mature.