Tree roots grow where they find water, air and loose soil, so near a house they go after leaking pipes, gaps and cracks that already exist, lift light paving, and on clay soil can add to the shrinking that comes with a dry summer. A big tree close to the house is worth watching, and a stump left against the wall is worth dealing with, because it rots into a void and a home for wood-loving insects.
What roots are actually after
Roots are not drills. A root tip grows where conditions suit it, and NC State Extension says roots grow toward air, water and nutrients. Near a house that means the soft soil of an old backfill trench, damp ground below a downspout or leaky spigot, and pipes with joints that seep. A root that finds a crack with moisture in it will fill it and widen it slowly as it thickens. So the questions to ask about a tree near your house are about water and gaps. Where does the roof water go? Are the drain and sewer lines old? Are there cracks already there? Fix those, and roots have much less reason to come close.
Clay soil and dry summers
Clay soils change volume with water: they swell when wet and shrink when dry, and the most reactive clays crack deeply in dry spells. A big tree takes a lot of water out of the ground in summer, so on reactive clay it can add to the drying under a shallow footing close by. How much this matters depends on your exact soil. The USDA's free Web Soil Survey lets you draw your lot on a map and read the soil types under it. Red clay subsoil is common across the Upstate and Piedmont, but soils vary lot to lot. If you see new or widening cracks, get a structural engineer to judge the cause before anyone blames the tree.
Pipes, walks and slabs feel it first
Light structures show root trouble long before a foundation does. A sidewalk slab, a patio, a garden wall or a driveway edge sits on a thin base, and a thickening root under it lifts it unevenly. Drain and sewer pipes are the other common target, since a seeping joint is food and water together. University of Maryland Extension notes that tree roots can grow into drain lines, which is just as true of a footing drain round a basement. A raised slab or a sewer backup is usually the first sign a tree has its roots under the house side of the yard. Those are the places to look before worrying about the walls.
Should the tree come down?
Not automatically. A healthy tree gives shade and holds soil, and taking it down can cause its own problems on clay, where ground that was kept dry by the tree gets wetter. Ask what is wrong. If roots are lifting a walk, the walk can be relaid. If a sewer line is full of roots, the line needs repair whether or not the tree stays. If the tree is too big for the spot, leaning, or dying, it should come out. A root system can run out to triple the width of the crown or more, so remember that a tree some way off may still reach the house. Tree still standing and you are unsure? Send a photo and we will talk through the options.
The stump against the wall
When a tree near the house is cut, the stump is the next problem. Left alone it rots for years beside your footing, and as the stump and its big roots decay they leave soft wood and then voids. NC State Extension says carpenter ants like wood that holds fifteen percent moisture or more, and lists removing dead or unhealthy trees near the home among its prevention steps. A rotting stump by the wall fits that description. Digging the root ball out beside a footing can undermine it, so grinding is usually the right tool there. The guide on stump grinding near a foundation covers how close a grinder can work.
Keeping a tree close to the house safely
If you are keeping a tree near the house, a few habits help. Send roof water well away from both the foundation and the tree's base. Keep limbs trimmed back: NC State recommends at least twelve inches between branches and the house to keep carpenter ants from walking across. Do not pile soil or mulch against the siding. When you add a patio, path or addition near a tree, Clemson Extension suggests routing lines around root systems, tunneling under roots instead of trenching through them, and setting additions on posts and piers instead of long footings. Those steps protect the tree and the house at the same time.
Who to call for which problem
Match the problem to the person. Cracks in a foundation or a wall that is moving are for a structural engineer, who can tell soil movement, settlement and roots apart. Roots in a sewer or drain line are a plumbing repair. A tree that is dead, leaning or too big for its spot has to come down with real care that close to a building. A stump left near the house, or roots and stumps in the way of a new patio or addition, is where JB comes in: stump grinding close to walls, or full removal where something is being built. On insects and stumps near the house, see carpenter ants in tree stumps.
Common Questions
Should I cut down a tree because its roots are near my foundation?
Not on that alone. Find out first whether there is a real problem: cracks that are growing, a lifted walk, roots in a sewer line. A healthy tree on stable ground can live beside a house for decades. Remove it if it is dying, leaning, or clearly too big for the spot, and have a structural engineer judge any cracks.
Do dead roots under a house cause settling?
They can cause small, local settling as they rot, mainly where a big root or a buried stump sits under a slab, walk or shallow footing. The wood shrinks as it decays and the soil above follows it down. Under open lawn it hardly matters. Under a structure, the wood should come out before building.
How far do tree roots spread from the trunk?
Much further than the branches. In NC State Extension's guidance a root system can reach out to at least triple the crown's spread, which for a big shade tree means a very wide circle. Most of them are shallow, in the upper couple of feet of soil.
What to Do Next
A stump hard against the house is a job for a narrow grinder that works from the side. Send a photo of the stump and the gap between it and the wall, plus your town, or call (828) 574-4474 for a free price.