There’s a big tree a few yards from the house, the patio beside it has a raised edge, and a crack has shown up in the wall on that side. The tree looks like the obvious suspect. Sometimes it is. Often the story is more mixed, and taking the tree down without knowing which story you’re in can cause a problem of its own.
This post covers the two different ways trees can affect a house, what the published research says roots can and can’t push around, why removing a tree isn’t automatically the fix, and what you can note before anyone picks up a saw. It’s written for homeowners across La Jolla. It isn’t an arborist’s report or an engineering opinion, and it can’t tell you what’s happening at your house.
Two different mechanisms
People tend to talk about roots damaging a foundation as one thing. Published sources describe two.
The first is moisture. Trees pull water out of the soil, and some soils shrink as they dry. We covered that cycle in how soil moisture cycles relate to settlement, including the California geotechnical guidance on trees and expansive soil. The UK’s Building Research Establishment put the mechanism in one line in its Digest 298 on trees and clay soils: “Soil shrinkage caused by the removal of water by trees and other vegetation can result in foundation subsidence.” In this case the roots never touch the footing. The tree changes the soil, and the soil moves the house.
The second is physical growth. A root gets thicker every year, and that growth pushes on whatever is next to it. A review of tree root conflicts by researchers from the USDA Forest Service Center for Urban Forest Research and UC Cooperative Extension says: “Forces exerted by radial growth of roots can lift light structures such as paths, curbs, paving slabs, boundary walls or occasionally single story buildings (e.g., garages or porches).”
Notice which things that list names. Walks, curbs, pavers and garden walls come first. Buildings come last, with “occasionally,” and the examples given are garages and porches. That review was written about sidewalks and roads, not houses, so it doesn’t settle any question about your home. It does suggest that a lifted patio next to a tree and a moving foundation aren’t necessarily the same problem.
Where roots usually are
Roots spread farther and sit shallower than many people picture. UC’s Statewide Integrated Pest Management Program says that lateral roots “often extend for a distance equivalent to two to three times the diameter of the drip line,” and that “Most roots will be found in the upper 2 feet of soil.” The Forest Service review says that “virtually all the large structural supporting roots, are in the upper 0.6 m” of soil, which is roughly the same two feet.
Roots also grow where conditions suit them. The review notes they “proliferate in areas conducive for growth,” including “near leaks where the infrastructure has been damaged.” A leaking pipe or a corner that irrigation keeps soaked can pull roots toward it. That’s one reason the water side of the question matters as much as the tree.
UC’s advice for new planting is plain: “Make sure large trees are planted away from buildings to reduce damage to foundations.” None of the sources we reviewed gives a single safe distance from a house. If someone quotes you a fixed number, ask where it comes from.
Why removal isn’t automatically the answer
Taking a tree out stops it drawing water. In soils that swell when wet, the ground can then take water back up. BRE Digest 298 describes that too: “Soil swelling caused by the recovery of moisture following tree removal can result in foundation heave.” So a house that settled while the tree was drying the soil can move the other way after the tree goes.
That digest is a UK publication from 1999, and its listing notes that some of its content has been superseded, so treat it as a description of the mechanism rather than local guidance. The mechanism still matters. Whether a tree should stay, be pruned, or be removed depends on the soil, the tree, and what the house has already done. That’s a question for an arborist and, where the house is moving, an engineer. It isn’t one to settle from the driveway.
Root pruning and barriers come up often. The Forest Service review is cautious about both: “Although root pruning is widely practiced, research has yet to document its impact on tree health, structural integrity, and longevity.” On barriers it says “Research has shown variable effects of root barriers on root distribution.” Those findings come from sidewalk and curb work, but they’re a good reason to want a qualified arborist involved before roots get cut near a tree you plan to keep.
Other causes that look the same
Cracks and lifting near a tree don’t prove the tree did it. The Forest Service review’s table of causes for raised pavement lists “Shrinking or swelling of soil, penetration of incompressible materials or tree root growth.” HUD’s Residential Rehabilitation Inspection Guide lists “soil heaving due to frost or excessive root growth” among settlement causes, and says that cracking in exterior concrete like walks and drives “rarely presents a structural problem to the building.”
Drainage, irrigation, leaks and the original grading can all produce similar patterns. Our post on exterior drainage maintenance covers the water side. Separating cosmetic movement from a structural problem is the subject of hairline vs. structural foundation cracks.
Street trees in La Jolla are the City’s call
Some large trees in front of La Jolla homes are street trees in the public right-of-way. The City of San Diego’s tree maintenance page says to report them through Get It Done: “If a city-maintained tree is causing damage to a sidewalk or property, this should be reported to the City.” It adds: “You may request a No-Fee Permit for trimming, removal, planting or root pruning following inspection by City staff.”
The San Diego Municipal Code’s street-planting rules (Chapter 6, Article 2, Division 6) say no one may remove, cut or trim a street tree “without a permit from the Park and Recreation Director.” Removal requests that aren’t for dead or hazardous trees are weighed under City Council Policy 200-5. If you aren’t sure whether a tree is a street tree, ask the City before anyone cuts. This post doesn’t cover trees fully on private land, which may involve other rules.
Roots and sewer laterals
Roots also find pipes. The City notes that “Tree roots can sometimes interfere with water and sewer plumbing,” and that “The property owner is responsible for maintaining the lateral from the property all the way to the connection with the sewer main.” A leaking lateral is also a source of water in the soil next to the house. If you have slow drains or repeat backups near a tree, having a plumber check the lateral is one way to rule a leak in or out.
What you can note before anyone acts
You don’t have to diagnose anything. A few observations make any visit more useful:
- Where the tree is relative to the house, and roughly how far its canopy reaches
- Whether cracks, sticking doors or sloping floors are concentrated on the tree side
- Whether the movement is in flatwork (patio, walk, driveway) or in the house itself
- Irrigation near the tree and the house, and any recent changes to it
- Any leaks, sewer backups or plumbing repairs on that side
- Whether a large tree nearby was removed in recent years
- Dated photos of cracks, so changes over time are visible
The Forest Service review notes that “Displacement of structures is usually progressive.” Dated photos are how you see whether something is changing. Our sinking foundation and foundation settlement repair pages describe what ongoing movement can look like. The foundation drainage page covers how water is managed around the perimeter.
For planting near the house, CalGeo’s homeowner guide on expansive soil says: “Avoid constructing planters immediately adjacent to house foundations. Keep sprinklers away from foundations. Consider drip irrigation.”
Cost factors, not prices
We don’t publish prices. What shapes the cost of work where trees are involved: whether movement is in flatwork or the structure, how much investigation is needed first (soil, drainage, plumbing), arborist and engineering input, any City permit for a street tree, access around roots, the repair approach chosen, and drainage or irrigation changes that come first.
Where we fit
We’re a foundation and structural repair company serving La Jolla citywide. On a visit we can document cracks, floor slope, drainage and where a tree sits relative to the house during a foundation inspection, and explain what we see. We aren’t engineers or arborists, and we don’t diagnose from photos. We work with verified contractors and coordinate with licensed engineers as needed. This post is general education, not an assessment of any property.
Next step
If a tree near your house has you worried, request a Free Quote for an on-site visit anywhere in La Jolla, or call (650) 739-6537. Hold off on removing or root-cutting a large tree until you know what’s actually moving.
Sources (accessed October 27, 2026)
- UC Statewide Integrated Pest Management Program (UC Agriculture and Natural Resources), “Provide for Roots”
- Jan Randrup, E. Gregory McPherson and Laurence R. Costello, “A review of tree root conflicts with sidewalks, curbs, and roads,” Urban Ecosystems 5 (2001), via USDA Forest Service Treesearch
- Building Research Establishment, Digest 298, Low-rise building foundations: the influence of trees in clay soils (1999), abstract
- U.S. Department of Housing and Urban Development, Residential Rehabilitation Inspection Guide
- California Geotechnical Engineering Association (CalGeo), Coexisting with Expansive Soil (2013)
- City of San Diego, Trees: Maintenance
- San Diego Municipal Code, Chapter 6, Article 2, Division 6 (Street Planting)
- City of San Diego Council Policy 200-05