Repair methods
Expansion-joint repair
The soft filler strips between my concrete sections have gone. Do they need replacing?
Usually yes, because they were doing a job that nothing else does. An expansion joint is a genuine gap, filled with compressible material, that lets concrete grow with temperature and isolates one element from another so they do not press on each other.
It is often confused with a control joint, and the two fail differently and matter differently.
What the method is
At every junction between a slab and a wall, step, column or earlier pour, an expansion joint provides a compressible gap so thermal movement does not transfer force between them.
The filler is deliberately soft. When it deteriorates or is removed, the gap fills with grit and soil, becomes incompressible, and the elements begin bearing on each other.
Repair means clearing the joint properly, replacing the compressible filler, and sealing the top against water and debris.
What it does not do
- It does not create isolation where none was detailed. If a slab was poured tight against a wall, a joint has to be cut in as separate work.
- It does not repair damage already caused by concrete bearing on concrete.
- It does not stop thermal movement; it accommodates it.
- It is recurring maintenance, not a permanent solution.
What you can safely check yourself
- Check whether the joint is packed solid. An incompressible joint is no longer an expansion joint.
- Look for spalling or crushing at the edges either side, which indicates the elements have been pressing on each other.
- Look at the joint where a slab meets the house, since that is both an isolation joint and a water path.
When professional evaluation matters more
- Edges either side are crushing or spalling, indicating significant transferred force
- A slab is bearing directly on a wall, step or column with no gap remaining
- The joint at the house is open and taking water down beside the foundation
Questions to ask whoever comes out
- Are you replacing the compressible filler or only sealing the top?
- How deep are you clearing the joint, and how?
- What material, and how much movement does it accommodate?
- Does the damage at the joint edges need repairing first?
- Is the joint against the house being detailed to shed water?
Where estimates for this commonly differ in scope
These are the places two prices for apparently the same work stop being comparable.
- Top sealing only versus full filler replacement are very different scopes commonly described the same way.
- Edge repair where concrete has crushed is usually separate.
- The joint against the house is both an isolation and a water detail, and estimates often address only one.
Usually worth planning a repair
Conditions in this band do not usually become emergencies, but they rarely improve on their own and repair costs tend to rise with the affected area.
Who tends to do this work
- A concrete repair specialist
- A residential flatwork concrete contractor
ConcreteOwner does not inspect, certify or approve contractors. This describes which trade usually holds this work, not a recommendation of anybody in particular.
Common questions
What is the difference between a control joint and an expansion joint?
A control joint is a deliberate weakness that decides where the slab cracks as it shrinks. An expansion joint is a real gap with compressible material that lets concrete grow and stops one element pressing on another. Shrinkage versus growth, weakness versus gap — different purposes and different failure modes.
Do I really need the soft filler replaced?
If the gap has filled with grit and soil, it is no longer compressible and no longer functioning. The consequence shows up as crushing or spalling at the joint edges where the two elements now bear on each other. Replacing the filler is cheap compared with repairing that damage.
Why does my patio press against the house?
Either it was poured tight with no isolation joint detailed, or a joint existed and has filled in. Either way, thermal movement in the slab now transfers to the wall. Cutting or restoring an isolation joint is the remedy, and it is worth doing before the pressure causes damage.
Where to go next
Related problems
Worth comparing
What drives the cost
Methods that may apply
Want a straight answer about expansion joint repair?
Both decision tools are free and need no contact details. If you would rather have somebody local look at it, you can ask us to review whether we can match you — and we will say plainly if we cannot.