Does underpinning fix cracks? It is one of the most common questions from homeowners facing a significant repair job, and the honest answer is: not directly. Underpinning stabilises the foundation that caused the crack to form. It stops further movement, which means the crack should not get any worse. But the crack in the wall, the opened mortar joint, the displaced plasterboard, none of that closes automatically when the footing is fixed below. Two separate jobs are involved, and understanding the right sequence matters. Book a foundation inspection first to confirm what the movement requires, then plan the repair in stages.
The two-step reality: stabilise, then repair
The fundamental reason cracks exist is that part of the structure moved relative to another part. The crack is the record of that movement: where the wall could no longer accommodate the stress, it opened. Underpinning addresses the source of the movement, the failing footing, by giving it new bearing capacity below the zone of soil instability. Done correctly, it removes the force that was pulling the wall apart.
But the wall has already been pulled apart. The bonds between mortar and brick that failed when the crack opened do not rebond when the movement stops. The plasterboard that tore or cracked does not rejoin. The paint that opened at the surface does not close. The physical gap in the material is permanent until a separate repair addresses it.
Think of it this way: underpinning is the equivalent of stopping a slow leak that has been damaging a ceiling. The leak stops, which prevents further water damage. But the ceiling stain that is already there does not disappear on its own. You need two interventions, not one.
Our underpinning service page explains what underpinning does from a structural perspective. Our foundation crack repair service covers what follows.
Why cracks don’t magically close after underpinning
Homeowners sometimes expect that lifting or stabilising a dropped footing will push the wall back into its original position and close the cracks as if they were never there. This happens occasionally and partially, but it is not the norm, for several reasons.
The movement was usually gradual and cumulative. Foundation movement on reactive clay in Wagga happens over months and years, not overnight. As the footing dropped, the wall accommodated the movement in small increments, and the material bonds failed progressively. Reversing this precisely in the opposite direction during underpinning is not how the method works. Underpinning stabilises at the current position; it does not wind the clock back.
Concrete underpinning pours to the current footing position. The new concrete bears against the underside of the existing footing at its current, settled level. It does not jack the footing back up to where it was. Some limited crack reduction can occur as the concrete cures and the new bearing settles in, but this is minor and not something to plan on.
Brick bonds and mortar once failed do not re-form. The structural bond between a brick and its mortar is formed during construction when the mortar is wet and cures around the brick surface. When a crack opens through that bond, the mortar is broken. Pushing the wall surfaces back toward each other does not re-establish that bond. Only new mortar, applied correctly to a clean crack face, does that.
For more on what crack patterns indicate about the movement history, see cracks in walls and when to worry and the dedicated guide to stepped cracks in brick walls.
When some crack closure does happen
It would be inaccurate to say cracks never close partially after underpinning. There are limited circumstances where some reduction in crack width occurs.
Screw pile or lift-and-restrain methods in specific designs: Some modern underpinning systems are designed with a controlled lift component. A hydraulic lifting bracket can apply upward pressure to a section of footing, restoring some of the lost elevation. When the wall above is lifted back toward its original position, cracks that opened in tension may partially close. This is not a universal feature of all screw pile jobs, and whether a lift is attempted depends on the engineering assessment and the structural condition of the wall above.
Slab relevelling via resin injection: When resin injection lifts a settled slab section back toward its design level, associated cracks in walls may partially close as the geometry of the structure is partially restored. Again, this is situation-dependent and the closure is rarely complete.
Elastic deformation in newer construction: In relatively new buildings with more ductile construction and less accumulated damage, some crack closure after stabilisation is more likely than in older masonry with stiff bonded layers.
In all cases, any partial crack closure should be seen as a welcome bonus rather than an expected outcome. Plan for separate cosmetic repair regardless.
The right sequence: underpinning first, cosmetic second
Doing the crack repair before underpinning is one of the more common and costly mistakes in this space. A homeowner sees a crack, finds it distressing, and pays to have it repointed and repainted. Six months later the crack has opened again, sometimes slightly worse than before, because the underlying movement continued.
The correct sequence is:
- Get a foundation inspection to confirm the cause and extent of movement
- Complete the structural repair, underpinning or the appropriate alternative, to arrest the movement at source
- Allow a monitoring period for the structure to settle on its new supports
- Confirm with a follow-up assessment that movement has stopped
- Commission foundation crack repair and cosmetic reinstatement
The concrete underpinning method page explains the structural work in detail. The crack repair comes after, and only after, the foundation is confirmed stable.
The one exception is emergency cosmetic repair to prevent immediate water ingress through a large external crack. A temporary flexible sealant applied to a wide open crack in an external wall while awaiting structural repair is pragmatic, not premature. Just be clear with any crack-repair contractor that this is temporary and that the surface will need to be reopened and properly repaired after the structural work is complete.
How long to wait before final crack repair
| Phase | What happens | Typical timeframe |
|---|---|---|
| Structural repair completed | Underpinning, resin injection or other method | Varies: 1-4 weeks for most residential jobs |
| Initial settlement period | New supports bed in, any minor continuing movement settles | 1-3 months |
| First monitoring check | Professional re-inspection to assess movement status | 3-6 months post-repair |
| Confirmed stable period | No measurable movement in two consecutive checks | By 6-12 months |
| Cosmetic crack repair | Repointing, render, plasterboard, paint | After stability confirmed |
The monitoring window of three to six months is commonly recommended by practitioners in the field, though the appropriate period depends on the extent of movement and the method used. Screw pile jobs that include a controlled lift may have a shorter monitoring window because the structure is immediately restabilised at its new level. Larger concrete underpinning jobs may need more time for the full sequence to be confirmed stable.
This waiting period frustrates some homeowners who want the house to look normal as quickly as possible. The risk of skipping it is cosmetic repair that fails within a year. Cracks that are repaired before movement has fully arrested will reopen. The monitoring period is not caution for its own sake; it is the practical insurance that the cosmetic repair lasts.
See how long does underpinning take for the full project timeline including the structural phase. For specific crack types including cracks above door frames, see cracks above doors and windows.
FAQs
Will my walls crack again after underpinning?
If the underpinning has been correctly designed and the underlying cause of movement (drainage, trees, soil moisture) has also been addressed, further cracking of the same origin should not recur. If the cause was not addressed, other sections of footing that were not underpinned may eventually develop similar problems. Underpinning is structural; causation management is a separate task that is equally important for long-term results.
Can a builder just repoint the cracks without underpinning?
Yes, and this is done regularly. Whether it is appropriate depends on whether the movement has stopped. If the footing is no longer moving (because the soil moisture has stabilised after a one-off drought event, or because the damage is historical and the house has been stable for years), repointing without underpinning is reasonable. If active movement is occurring, repointing without structural repair will fail. A foundation inspection is the correct way to determine which situation applies.
Does underpinning level my house again?
Standard concrete and screw pile underpinning stabilises the footing at its current settled position; it does not restore the house to its pre-settlement level. Some controlled-lift systems can partially restore elevation, and this is sometimes possible as part of a screw pile job. Whether a lift is achievable and safe depends on the structural condition of the house and the engineering assessment. Discuss this explicitly with the contractor during the quoting stage.
How much does crack repair cost after underpinning?
Cosmetic crack repair after underpinning varies widely with the extent of damage, the material involved and the finish required. Repointing mortar joints in brickwork is relatively modest. Full render repair, plasterboard replacement and repainting a significant area of wall is more involved. It is a separate cost from the structural work and should be budgeted separately when planning the full scope. Get a quote from a builder or renderer after the structural work is confirmed complete, not before.
Can I do the crack repair myself?
For hairline cosmetic cracks in internal plasterboard, filling and painting is well within most homeowner capabilities. For external brickwork repointing, mortar matching, or any crack repair that has a structural component such as crack stitching, using a qualified tradesperson is advisable. Incorrect mortar specification in external repointing can cause water infiltration problems over time.