Landscaping & Design/Root Barriers


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to the soil then swelling occurs,which can cause the foundation to move and crack and similarly,if too much water is withdrawn from the soil,the foundation can move.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

---------- 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!


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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Design of landscape structures and design of planting arrangements in the landscape. I usually do not answer questions of a horticultural nature or about growing plants or gardening unless they are related to design. I will answer these questions at my discretion. I will answer maintenance questions at my discretion,usually when they are related to design. I am a landscape designer. I am not a contractor or a gardener. Although I will describe how something is built I do not provide detailed installation or construction instructions. Here are example categories of problems I can help you with: Design of residential walks,low walls,low retaining walls,fences,drainage systems,arbors,plant selection,xeriscapes (low water use landscapes),rain garden design,rain water harvesting,permeable paving,sustainable drainage. No advise on an architectural or engineering level. I DO NOT PERFORM ACTUAL DESIGN WORK THROUGH THIS SITE. I only provide suggestions and advice. For more comprehensive help check out my website at:


Landscape concept plan for a 30,000 square feet housing site. Involved site recon by pace measurements and photographs and a site analysis and a site analysis report and recommendations and a preliminary cost estimate. Design elements included canopy trees,shrub cover,accent flowers,trash receptacles,benches and planters. Landscape concept plan for a 7,000 square feet site for a community center. Involved site recon by tape measurements and photographs,a site analysis and the creation of 3 conceptual designs for the site. Work was done through a local professional design center. Design elements included tree garden,playground,sitting area,lawn,cooking area,lighting and concrete and brick paving. Landscape concept plan for a 3,000 square feet housing site. Involved site recon by tape measurements and photographs and a site analysis. Concluded in 3 concept designs for the site,shown at a formal presentation,a site analysis and recommendations. Work was done through a community volunteer program. Design elements included decks,a playground and fencing. Briefly as draftsman for landscape designer/gardener. Conceptual landscape design for residence. Involved site recon by tape and pace measurements and site analysis. Design included covered patio area,ground cover and flower beds. Two years experience as draftsman for transportation department in engineering firm and for engineering consultants to phone company. Duties consisted of plotting topography. Survey crew member. General assistant to surveyor. Work was done for U.S. Army and County Highway Department. No instrument work. Duties included tape measurement,holding graduated survey rod and plumb bob for sighting and clearing brush. Marketed Landscape Design Services. Brochure writing,promotional material and marketing graphics.

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