QuestionI have a similar question to the one you answered in 2007. We are adding an addition to our home and have a large fir tree about 100 feet tall and 2 feet in diameter. The trees is 10 feet from where the foundation will be. My plan is to put something wet over any exposed root and cover them with plastic during construction and if necessary put plywood over them so they will not be damaged. I am pretty sure we will have to cut some roots but will keep it to a minimum. What do you think?
AnswerIf you not dig up more than 25-30 % of the root system this will damage the tree and cause dieback of the foliage. The root system spread is about 1 1/2 times the width of the branches. You can draw a circle around the tree at the branches ends and over lap the part that will be damaged by construction and if it exceeds 25-30% you will get foliage damage. When you dig the foundation cut the roots off clean not just break them off. The ends of the cut places will heal over and there is not need to keep them wet. The rest of the root system needs to be protected from ANY machinery--keep all machines off from around the tree to stop compaction. You will need all the rest of the root system to keep the tree alive. I would rope off this area not just put plywood over it--Plywood assumes there will be traffic on this area --not a good idea.
