Question
QUESTION: I have been told by a foundation repair company that the hollies planted near my foundation take more water out of the foundation than a tree and they should all be pulled out.  Do you agree they should not be planted around foundations?  

Thank you for the opportunity to ask a question.

ANSWER: Hello,

Doesnt sound very likely that you could have enough hollies to match the water holding capacities of a tree but in general all shrubs should be kept a minimum of 5 feet from the foundation wall and trees should be kept a minimum of 15 feet or the distance of the canopy spread from the wall. keep shrubs 5 feet from the wall in order to avoid problems caused to the foundation wall by watering the shrubs.

Trees can remove enough water from the soil and cause problems if they are planted too close to the foundation wall. Water problems of this nature (shrink/swell) occur with sensitive clay soils. If too much water is added to the soil then swelling occurs,which can cause the foundation to move and crack and similarly,if too much water is withdrawn from the soil,the foundation can move. This movement is known as differential movement. Movement is promoted by having a wet area next to a dry area. When there is a uniform,evenly distributed state of moisture,movement is less likely. Water problems of this type are not likely with loam/sand soil or gravel fill.

You may be fine with leaving the holly in place if you have good drainage around the wall. Watering the holly would not have anymore effect than rain. Depending on the situation some foundation walls will have moisture problems where others will not. Some walls need only a footing drain while others may benefit from an impermeable layer,such as a concrete apron around the perimeter,a FIN drain and waterproofing.  Water can have a damaging cumulative effect over a period of years,however. Considering this fact,it is always a good idea to keep as much water as possible away from foundation walls. Some houses have roof overhangs that may provide all or most of the protection that an impermeable perimeter apron would provide.  Good luck. Let me know if I can be of further help.

Mark Harshman
http://www.harshmandrafting.com

http://www.scribd.com/markscrib47
Email: [email protected]

---------- FOLLOW-UP ----------

QUESTION: Thanks for your time Mark.  I have another question....what are your thoughts on root barriers for trees?   I have a 22 yr old tree about 15 feet from the foundation and have been advised I need to put in a root barrier between the tree and house for the tune of approx $600.  My soil is CLAY -North Texas!

Answer
Hello,

I place no faith at all in root barriers. They do not have a proven track record and often in fact, the tree roots simply go under the barrier or over it in search of water. These barriers have proven useful in clay soil because they can cause the clay to retain water and keep the water content of the clay in a balanced state. If you have heavy clay around your foundation wall,then such a barrier may be useful for that purpose. It may cost about the same or a bit more to have the tree removed if it becomes a problem, rather than use a root barrier.

The tree roots are not likely to damage your foundation wall or remove an appreciable amount of water from around the wall. In their natural state,tree roots spread out close to the surface in order to collect water and nutrients and since a root barrier forces the roots downward,there is some concern that root barriers are not healthy for trees. The main idea is to use the right tree in the right place and so expensive "fixes" like root barriers will not be necessary. Good luck. Let me know if I can be of further help.

Mark Harshman



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