QuestionI have a large Douglas fir located 12 feet from my house's stem-wall type foundation. I'm estimating the tree at 80 feet in height with a trunk approximate 30 inches in diameter. A nearby (approximately 4 feet) cement slab patio has been lifted by the tree roots, should I worry about my house foundation? I estimate there is less than two feet of topsoil over laying a blue clay.
AnswerA stem wall foundation has a footing depth that is usually below the frost level. The roots of most trees are in the first two feet of soil and I would think the footing is below this level. The roots should not cause any problems to your foundation. Also the branch spread of the Doug fir is about 20 feet meaning the branches will extend about 10 or so feet from the trunk--the roots will extend about 1 1/2 times the width of the branches. BUT these roots on the outer most part are not large and usually can not lift anything. Also the slab is much thicker that the patio slab so overall I would not expect any damage from the root system.
