Concrete driveways
Last Updated:
Driveway expansion joint repair replaces the failed filler in the gaps between concrete slabs with a flexible seal, so the slabs can still move and water, grit and weeds stay out. The joints are the part of a concrete driveway designed to give, and when their filler rots or packs with debris, the concrete around them starts taking damage instead. Sundial Driveway Repair is a service company offering and managing driveway expansion joint repair across Phoenix and the surrounding Valley, for homes and commercial properties, fulfilled by licensed and insured contractors.
Joint work is concrete-only. Asphalt has no designed joints, and the seam where an asphalt drive meets a concrete garage slab or apron is sealed as a crack; driveway crack repair covers that.
The first visit looks at the whole drive: the surface, every joint, the edges, where water runs, and the transitions at the garage, sidewalk and street. Each joint is identified by type and checked for what is in it now: original wood or fiberboard, old sealant, sand, weeds or nothing. Joint edges are checked for chips and spalls, and the panels on each side are compared for height, since a step at a joint means a panel has moved and sealing alone won’t fix it. Cracks nearby are checked for width, offset and whether they cross panels.
The estimate names the work for each joint type, the total length and what the work excludes. If a joint turns out to hide a settled panel or soft base, that finding is explained before the joint work is priced, because sealing over a moving joint just tears the new sealant.
A control joint is a groove saw-cut or tooled into the slab, usually a quarter of its depth, to make it crack in a straight line. Concrete shrinks as it dries and cures, and the shrinkage has to go somewhere; the groove weakens the slab at that line so the crack forms under it, out of sight, instead of wandering across the panel. A driveway’s panels are the spaces between its control joints. A crack running through a joint, below the groove, means the joint is working as designed. A crack crossing a panel away from the joints means the joints were too far apart, cut too late or too shallow, or the slab moved for some other reason. The guide to why driveways crack and sink traces those causes.
An expansion joint, more precisely an isolation joint, is a full-depth gap between the driveway and something it shouldn’t be bonded to: the garage slab, the sidewalk, the curb, a wall or a column. It is formed when the concrete is placed, with a strip of compressible filler such as asphalt-impregnated fiberboard, felt or, on older drives, a wood board. Its job is to let each slab expand and settle on its own. Without it, a driveway expanding in the heat pushes against the garage slab or the sidewalk, and one of them cracks or lifts.
Heat is the driving force. Concrete expands as it warms, roughly 1/16 inch over a 20-foot panel for a 50°F rise, and it does that every sunny day. At Phoenix Sky Harbor the normal July high is 106.5°F and 111 days a year reach 100°F or more (NOAA climate normals), so the joints open on cooler nights and close in the afternoon for much of the year. The guide to how heat affects driveways in Phoenix explains the mechanism further.
Original fillers don’t keep up. Wood boards rot where irrigation keeps them damp. Fiberboard and felt crumble, shrink back below the surface and leave an open slot. That slot fills with sand, grit and seed, and the trouble starts. When the slab expands against incompressible debris instead of soft filler, the force goes into the joint edges, which chip and spall. Water poured into an open joint by sprinklers or roof runoff reaches the base, and in clay soils that wets and dries the ground under the joint unevenly. In USDA soil survey samples, more than three of every four points in Gilbert and Chandler show moderate or higher shrink-swell clay, so a joint that passes water can become a joint with a step.
The old filler comes out first. Wood and fiberboard are cut and pulled, old sealant is cut free, and the joint is cleaned with a wire wheel or saw so the faces are sound, dry concrete. A closed-cell foam backer rod, slightly wider than the joint, is pressed in to set the depth. The rod does two things: it stops the sealant from bonding to the bottom, so it only grips the two faces and can stretch between them, and it keeps the sealant from being too deep to flex. An elastomeric sealant meeting ASTM C920, usually polyurethane or silicone, is then placed. Self-leveling grades are poured on flat joints; non-sag grades are tooled on sloped ones. The bead finishes just below the surface so tires and brooms don’t catch it, and tape keeps the concrete beside it clean.
Mortar, concrete and rigid patching compounds don’t belong in a movement joint. They bond the slabs together and remove the joint, and the next heat cycle cracks the concrete beside it. Chipped edges are repaired with a patching compound first, then the joint is re-formed and sealed. Sealant ages in the sun and will need renewing at some point, which is ordinary maintenance.
A step at a joint means a panel settled or heaved, and the support has to be dealt with first. A sound panel that dropped can be raised with driveway leveling; a small, stable lip can be removed by trip hazard grinding; a broken panel is replaced, as concrete driveway repair explains. Joint sealing comes last in each case.
The joint between the driveway and the sidewalk may sit in the street right-of-way. In Phoenix, City Code makes the owner of a lot abutting a sidewalk responsible for keeping it in repair, and the guide to who is responsible for the driveway apron covers that strip. Sealing a concrete driveway’s surface is a separate service; driveway sealing covers sealers and how they relate to joints.
Joint repair is priced from the length of joint and what each one needs, so there is no single per-foot figure that fits every drive. Wide isolation joints use more backer rod and sealant than saw-cut control joints, removing old wood or fiberboard adds time, spalled edges add patching, and a short list of joints is usually set by a minimum charge. The driveway repair cost guide explains how small repairs are priced. Concrete joint work falls under Arizona’s R-9 and C-9 concrete classifications, and whether insurance pays for any repair depends on the policy and the cause. When you’re ready, ask for an estimate.
| Repair | Best for | Won't fix | How it's priced |
|---|---|---|---|
| Replace failed filler with backer rod and sealant | Isolation joints with rotted wood, crumbling fiberboard or missing filler | Panels that have dropped or tilted at the joint | By the linear foot of joint, after measuring width and depth |
| Seal open control joints | Saw-cut joints that collect grit and let water reach the base | Cracks running across panels away from the joints | By the linear foot, often grouped with other joints |
| Patch spalled joint edges, then seal | Joint edges chipped by debris or traffic | A slab still moving at the joint | Per job after measuring the damaged length |
| Lift or replace a panel, then seal | Joints with a step where a panel has settled | Nothing structural once the support is rebuilt | Lifting or section replacement rates, plus the joint work |
Guides that go deeper on expansion joint repair decisions in the Valley.
The physics of a slab that grows and shrinks every day, why heat does its worst damage to concrete in the first hours, how asphalt binder softens and ages under Valley sun, and what owners can do through a long summer.
How a driveway is built, what the Valley's heat, soils and storms do to each layer, how to read the cracks you can see, and when a repair can wait.
Typical Phoenix-area and national budgeting ranges for each kind of driveway repair, what is inside the price, the City permit fees, and worked example budgets.
Describe the surface, what changed and roughly where the property is. Photos of the damage and the street edge help. The published ranges give you a budget to think about before any visit.
The visit looks at more than the damaged spot: the slab or asphalt, the joints and edges, where water runs, and the transitions at the garage, sidewalk and street. The damaged area is measured, and anything found that changes the scope, such as soft base or caliche, is explained in the estimate.
Hot-weather practice from the American Concrete Institute caps concrete at 95°F at discharge for general work, so summer pours are planned for the cooler part of the day. Where the job crosses into the street right-of-way, the city's permit is part of the scope.
How long the car stays off depends on the material and the temperature. That wait is set out before the work starts, so you can plan around it.
Joints rotted or full of weeds? Get an Estimate.
Send photos of the joints at the garage, sidewalk and curb, and rough lengths. The estimate lists each joint, what it needs and any edge repair first.
The wood comes out completely, down to sound material or the base. The joint is cleaned, a closed-cell foam backer rod is pressed in to the right depth, and an elastomeric sealant is placed over it. That combination stays flexible, keeps water and weeds out, and can be cut out and renewed later without damaging the concrete.
That gap is an isolation joint, and it is meant to stay flexible. The old filler is removed, the faces are cleaned, backer rod is set below the surface, and a self-leveling sealant is poured over it. Filling it with mortar or concrete locks the two slabs together, and the next hot spell can crack one of them.
It depends on the joint and where water goes. An open saw-cut joint collects sand and grit, and where sprinklers or roof water cross the drive, it also lets water into the base. Sealing those joints keeps both out. A narrow tooled joint on a slab that sheds water well can be left open and kept clean.
Because the filler has failed and soil and seeds have washed into the space. Weeds are a sign that the joint is also passing water down to the base. Pulling them treats the surface; removing the old filler, cleaning the joint and sealing it is what stops them returning.
By the length of joint, adjusted for what each joint needs. Wide isolation joints take more backer rod and sealant than narrow saw cuts, removing old wood or fiberboard takes time, spalled edges need patching before sealing, and small jobs carry a minimum charge. The estimate lists each joint type, its length and the work it gets.
Driveway crack repair in Phoenix for concrete and asphalt: dormant vs working cracks, filling vs sealing, and when a crack points to the base.
Concrete driveway repair in Phoenix matched to the cause: cracks, spalling, broken edges and sunken panels, with local price ranges and rules.
Phoenix concrete sealing for driveways and pavers: penetrating vs film-forming sealers, how sun and heat wear them, and what sealing can't fix.
Tell us the surface, what changed and the nearest cross streets. Photos of the damage and the street edge make the estimate more useful.