Root Barriers and Home foundations - Ask Extension
I am doing research on putting in a root barrier between my home's foundation and two large trees in my front yard. We have been experiencing some fo...
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Root Barriers and Home foundations #164667
Asked January 20, 2014, 2:29 PM EST
I am doing research on putting in a root barrier between my home's foundation and two large trees in my front yard. We have been experiencing some foundation movement and our structural engineer has suggested either removing the trees or installing a root barrier. One tree is a magnolia and the other is a large live oak. The two trees' trunks are approximately 17 feet out from the foundation of the house. There is a bed in front of my house that comes out six feet from the foundation. My Landscaper is suggesting that I put the root barrier just outside the bed which would be about 11 feet from the trunks of the trees. My questions are as follows:
How close to the foundation does the root barrier need to be; would 6.5 feet away from the foundation be ok or should we go inside the bed?
Would 11 feet from the trunk give the tree enough anchor roots on the root barrier side?
How deep does the root barrier need to be to protect the foundation? My Landscaper thinks 24 inches is adequate but the structural engineer is suggesting 48 inches. The only information I could find on this was an article from Texas A&M ( http://aggie-horticulture.tamu.edu/newsletters/hortupdate/hortupdate_archives/2002/mar02/art3mar.html )it said that the root barrier needed to be at lease 30 inches. Root barriers are sold in 24, 36 and 48 inch depths. The deeper you go the more expensive they are to install. I want to know if the 36 inch would be adequate.
Any other information would be helpful.
PS the photos I have attached are a little dated. Both the bush left of the front door and the yaupon in the front bed have been removed.
How close to the foundation does the root barrier need to be; would 6.5 feet away from the foundation be ok or should we go inside the bed?
Would 11 feet from the trunk give the tree enough anchor roots on the root barrier side?
How deep does the root barrier need to be to protect the foundation? My Landscaper thinks 24 inches is adequate but the structural engineer is suggesting 48 inches. The only information I could find on this was an article from Texas A&M ( http://aggie-horticulture.tamu.edu/newsletters/hortupdate/hortupdate_archives/2002/mar02/art3mar.html )it said that the root barrier needed to be at lease 30 inches. Root barriers are sold in 24, 36 and 48 inch depths. The deeper you go the more expensive they are to install. I want to know if the 36 inch would be adequate.
Any other information would be helpful.
PS the photos I have attached are a little dated. Both the bush left of the front door and the yaupon in the front bed have been removed.
Dallas County Texas
Expert Response
Great questions. I'll try to address them one at a time.
As for the distance of the root barrier from the house/tree, there are a couple of things you probably need to consider. First, I think that leaving a few feet between the barrier and the foundation of your home is a good idea. Essentially, the tree's roots will affect your foundation not by physically lifting your house, but by drying the soil around your foundation and causing shrinking and swelling of the heavy clay soils in your area. This causes your foundation to settle and move and can cause cracking and damage. Having a "buffer zone" between your home and the root barrier should be helpful as the tree will have less of an impact on soil moisture around your foundation. Second, I think you're asking the right question about anchoring roots, etc. A tree's root system can extend 2-5 times the height of the tree from the base of the trunk (i.e. a 100 foot tree could have 200 to 500 feet of roots extending from the base of the tree). As long as you're staying at (or as near as possible to) the drip line of the tree, you should be OK. For a tree the size of your Live Oak, I would think you would be fine at 11 feet AS LONG AS you provide enough water for root re-growth and don't trench 180 degrees around the trunk. In fact, the less roots you're able to intercept with your trench, the better.
As for depth, everything I've read indicates that you should be in good shape with your 36 inch barrier. Generally speaking, 80-90% of your tree's root system can be found in the top 18 inches of soil where oxygen is available. That number could be even less in moist clay soils where oxygen doesn't move down as easily. Oaks do tend to have deep root systems, though, so the difference between the 36 and 48 inch barrier is probably negligible considering the deeper 10-20% of your root system. Overall I think you're fine with installing your root barrier 11 feet out from your Magnolia.
I definitely think you're headed the right direction and am glad to hear you're going the "root barrier" route rather than "accumulate large amounts of firewood" route. I always hate to see trees cut down when it can be helped (I live in Lubbock and they're a rare commodity around here). I hope this helps and please don't hesitate to ask if you need further information. Thanks!
As for the distance of the root barrier from the house/tree, there are a couple of things you probably need to consider. First, I think that leaving a few feet between the barrier and the foundation of your home is a good idea. Essentially, the tree's roots will affect your foundation not by physically lifting your house, but by drying the soil around your foundation and causing shrinking and swelling of the heavy clay soils in your area. This causes your foundation to settle and move and can cause cracking and damage. Having a "buffer zone" between your home and the root barrier should be helpful as the tree will have less of an impact on soil moisture around your foundation. Second, I think you're asking the right question about anchoring roots, etc. A tree's root system can extend 2-5 times the height of the tree from the base of the trunk (i.e. a 100 foot tree could have 200 to 500 feet of roots extending from the base of the tree). As long as you're staying at (or as near as possible to) the drip line of the tree, you should be OK. For a tree the size of your Live Oak, I would think you would be fine at 11 feet AS LONG AS you provide enough water for root re-growth and don't trench 180 degrees around the trunk. In fact, the less roots you're able to intercept with your trench, the better.
As for depth, everything I've read indicates that you should be in good shape with your 36 inch barrier. Generally speaking, 80-90% of your tree's root system can be found in the top 18 inches of soil where oxygen is available. That number could be even less in moist clay soils where oxygen doesn't move down as easily. Oaks do tend to have deep root systems, though, so the difference between the 36 and 48 inch barrier is probably negligible considering the deeper 10-20% of your root system. Overall I think you're fine with installing your root barrier 11 feet out from your Magnolia.
I definitely think you're headed the right direction and am glad to hear you're going the "root barrier" route rather than "accumulate large amounts of firewood" route. I always hate to see trees cut down when it can be helped (I live in Lubbock and they're a rare commodity around here). I hope this helps and please don't hesitate to ask if you need further information. Thanks!
