Water and clay cause most concrete trouble in the Diablo Valley. Clay swells when wet and shrinks when dry, so the goal is to keep the moisture under a slab as steady as possible and to send rain somewhere on purpose.
Do I need to worry about drainage?
Yes. Drainage is the first thing we plan. Our rain comes in a few months, sometimes in heavy bursts, onto ground that soaks it up slowly. Every slab needs a slope, and the water needs a destination: the street, a planted area or a drain. Water that ponds beside a slab feeds the clay and lifts the edge.
My patio or driveway slopes toward the house. What can be done?
Change the direction of the water. If the slab is sound, a channel drain cut in near the house can catch the flow and pipe it away. A slab that has settled toward the house or garage can sometimes be lifted back to the right pitch. If neither works, the section by the wall is removed and repoured with a fall away from the foundation. Water against a foundation on clay should not be left alone.
Can tree roots crack or lift concrete?
Yes. Tree roots grow thicker each year and lift whatever is on top of them. They also dry the clay nearby in summer, which lets a slab drop. Sidewalk panels beside street trees and driveways next to oaks, liquidambars and ash trees are the usual cases in Concord.
Can I fix the concrete and keep the tree?
Often you can keep the tree. Options include moving the path away from the trunk, using a thinner reinforced section that bridges a root, raising the grade a little or using pavers in that spot. Cutting a large root can destabilise or kill the tree, so we do not do that on our own judgement. Concord and several nearby towns protect certain trees, and an arborist's advice or a city permit may be needed.
My neighbor's concrete sends runoff onto my property. What can I do?
Start by talking with the neighbor and showing photos taken during rain. In general, a property owner should not redirect or concentrate water onto the next lot in a way that causes damage. A drain or a small curb on their side often settles it. If talking fails, a letter, mediation or a lawyer is the next step. This is general information and not legal advice. We can design the drainage fix for either side.
Does clay or soft soil change the job?
It changes most of it. On expansive clay we dig deeper, lay a compacted rock base, use steel, space the joints closer and keep landscape water away from slab edges. For a building slab or a tall wall, a soils report tells the engineer how much the ground is expected to move. Soft fill near the bay shore calls for removal or deeper support.
My gravel driveway turns to mud every winter. What is the fix?
A gravel driveway on clay turns to mud because the stone sinks into the wet soil. One fix is to regrade it with a crown, lay fabric and add compacted base rock. The lasting fix is to pave it. Concrete over a compacted base ends the mud, and a strip drain at the low end deals with the water.
My patio was poured over a utility trench and it settled. Why?
The trench was backfilled loose. Soil put back in a trench without compaction in layers keeps settling for years, and the slab over it cracks along both sides and dips. The fix is to cut out the strip, dig out the loose fill, compact it in layers and repour with dowels into the slab on each side.
I am in a flood-prone area and want a raised patio or slab. What should I know?
Check the flood map before you design it. Parts of Concord near the Walnut Creek, Pine Creek and Galindo Creek channels are in mapped flood zones, and filling or building in a flood zone has rules. A raised slab must not block the flow or push water onto a neighbor. Ask the City of Concord about your address. We could not confirm the local limits online.
Do earthquakes damage driveways and patios?
Strong shaking can crack flatwork, most of all on fill and slopes. The Concord Fault runs through the city. Flatwork is not engineered for earthquakes the way a building is, but steel in the slab and good joints help it stay together. Foundations and retaining walls follow the seismic rules of the California Building Code.
The real number for your job comes from a free visit, where we measure and look at the ground. Call (925) 690-1468 or text a photo of the area.