Cold joints, construction joints and kicker joints

A joint is not a crack, and it does not price like one

A crack is a fracture through a single element. It has two faces, a measurable width, and a finite volume. Once you have filled it, it is full, and refusal at the pump tells you so.

A construction joint is an interface between two separate pours. It can run the full length of a wall, turn a corner, tie into the kicker joint at the slab, and connect to every penetration and box-out that crosses it. Water entering at one end can travel along that interface and exit ten metres away at the lowest weak point, which is why the wet patch on the inside face is so often nowhere near where the water actually gets in.

That difference is the whole reason a joint carries a higher rate per linear metre than a crack. The joint takes more resin, because the path is wider and connected. It takes closer packers, because you are building a continuous plug along a line rather than filling a discrete void. And it takes volume discipline, because an open joint that breaks out into a void or a drainage layer behind the element will accept resin indefinitely without ever sealing the face. We set a hard volume stop per packer, in the order of one to two litres, and move on rather than pumping a drum into the ground and calling it progress.

The four joint lines that actually leak in SEQ

Before anything is priced, the leaking line has to be identified as one of these, because the set-out and the resin sequence differ between them.

• Kicker joint. The horizontal joint at the base of a wall where it meets the floor slab. In a leaking basement this is usually the real entry point even when a crack higher up the wall is what everyone is looking at. Drilled at 45 degrees down through the wall to intersect the joint, or vertically into the slab to intersect it, at 200-400 mm centres.
• Horizontal cold joint in a wall. The line between two lifts of the same wall. Often visible as a faint colour or texture change with efflorescence tracking along it. It leaks along its whole length rather than at a point.
• Structural slab to topping interface on a suspended deck. Water enters through the topping at one location and travels between the two slabs before dripping out of the soffit somewhere else entirely. On these, mapping matters more than injecting - inject the wrong end of the path and you have sealed a metre of a joint that was not carrying the water.
• Joints at penetrations, box-outs and construction stop-ends. The joint is interrupted, and the interruption is the weak point. These usually take a discrete per-point price rather than a linear metre rate.

When the cast-in waterstop has already failed

A waterstop is a strip cast into the joint at the time of the pour so that the joint carries a built-in barrier. When it does its job, nobody ever hears about it. When it does not, the reasons are usually mundane: it was displaced or folded over during placement, the concrete did not consolidate around it, or it was lapped rather than properly jointed at a corner or a junction and the lap has opened.

You cannot repair a cast-in waterstop from the dry side. What injection actually does at a failed waterstop is build a second, independent barrier alongside it. That changes the set-out. The drilled holes should intersect the joint on the dry side of the waterstop rather than pass through it. A drill bit through a PVC waterstop does not improve it, and afterwards nobody can say which barrier is holding.

Which means somebody has to know where the waterstop sits within the wall thickness before the first hole is drilled. That is a drawing, a scan, or a carefully placed trial hole - and it is a question worth asking at tender rather than discovering on day one.

The joint we will not inject

Expansion joints, control joints and panel-to-panel joints are designed to move. Filling one with resin defeats the purpose it was built for and transfers that movement into the adjacent concrete, which then cracks. You have not fixed a leak; you have moved a crack from a place where it was managed to a place where it is not.

Cured polyurethane makes this worse rather than better. It is a semi-rigid to flexible closed-cell foam, not an elastomer. Its elongation is low, so under continued cyclic movement it will simply be torn open, usually within a season or two of thermal cycling. Acrylate gel has far higher elongation and copes with real elastic movement, but it is still not a joint system and it has zero structural strength.

The correct scope for a leaking designed movement joint is joint preparation, the correct backing rod, and a movement-capable sealant or a proprietary joint system. That is a sealant scope with a sealant's design life and a sealant's maintenance cycle. If the joint is marked as a movement joint on your drawings, we will quote it that way or hand it to whoever does that work.

Set-out and sequence, in the order it happens

1. Prove the line before it is pricedExpose the joint. Render, paint and linings hide both the true extent and, on a deck, whether you are looking at the structural slab joint or the topping. Exposure is quoted as a separate item, because it is a separate cost and pretending otherwise is how contractors lose money on joint work.
2. Scan, then set the offsetGPR or a cover meter on any structural element. Mandatory scanning and written engineer approval before drilling any post-tensioned slab. Offset the hole from the joint line by roughly half the element thickness so a 45 degree hole intersects the joint at mid-depth: on a 250 mm wall, about 125 mm off the line.
3. Drill at 45 degrees, two thirds to three quarters deepA 13 mm bit for the standard 13 mm mechanical packer, alternating either side of the joint in a stitch pattern. Drill to roughly two thirds to three quarters of the element thickness and never break through the far face, or you lose all pressure and inject into the occupied space or the ground behind. On-tool dust extraction or wet drilling - the workplace exposure standard for respirable crystalline silica is 0.05 mg per cubic metre, and an enclosed basement is the worst place in the building to ignore it.
4. Set mechanical packers at 200 to 400 mm centresMechanical packers seal inside the wall body and deliver resin into the joint. Surface ports glued to the face put resin onto the wall, and the surface seal will not adhere to a wet joint anyway. A useful spacing rule: centres should not exceed the element thickness, and about half the element thickness is the safe default on critical work.
5. Water-flush and prove the joint is connectedFlush clean water through each packer before injecting. It proves the joint is hydraulically connected from one packer to the next, which is the only real test of whether the spacing is right. It also clears laitance, efflorescence and calcite out of the joint - deposits that would otherwise block resin penetration entirely. If water does not appear at the next packer, the set-out is wrong, and that is the moment to find out.
6. Inject in one consistent direction, killing gushers firstOn a horizontal joint, work consistently from one end to the other. On a vertical crack intersecting it, bottom to top so resin displaces water upward and out. Kill any single gushing point first with a fast-set hydrophobic dose, hydraulic plug or oakum to reduce flow, then return and inject the joint methodically. Start at the low end of the 35 to 140 bar band and escalate only as the joint needs it. Move on when resin appears at the next packer or you reach refusal.
7. Cut back at 24 hoursLeave packers in for a minimum of 24 hours, then cut the shafts 10 to 20 mm below the surface and fill with a non-shrink hydraulic plug or polymer-modified mortar.

Retrofitting a re-injectable hose along a joint

Re-injectable hose systems are normally a new-build item, cast into the joint so the joint can be grouted later without drilling. On remedial work the same idea can be retrofitted: a small-bore hose fixed along the joint line in a cut chase and encapsulated, with injection and vent ends brought out to accessible points, so the joint can be re-treated in future without a fresh set-out.

The chemistries specified for hose systems are hydrophilic polyurethane and acrylate gel, because both can be pumped repeatedly through a small-bore line and both tolerate being re-wetted. Hydrophilic materials also re-swell when water returns, which suits a joint that only runs in a wet season.

Be honest about when it earns its cost. Cutting a chase and encapsulating a hose is a bigger surface intervention than drilling packers, and the whole benefit is future re-access. It pays where the joint is about to be buried behind a fit-out, where the joint is in a tank that cannot be taken offline twice, or where the access cost is the dominant line item. On an accessible car park joint that you can walk up to again next year, it is over-specification.

What to write into the specification as evidence

Joint injection is a scope where the difference between good and cheap work is invisible the day after it is finished and obvious after the next wet season. Specify the evidence, not just the method.

• Resin observed at the adjacent packer - this is the direct proof of travel along the joint.
• Photographs before and after, taken from the same positions, with a written description of what was found and what was done.
• Moisture meter readings at marked points before and after, so verification is a number rather than an opinion.
• Observation over a minimum of 24 to 48 hours and, where the program allows, across a rain event before handover.
• An explicit statement of what the warranty covers. Sealing from the dry side redirects water rather than removing it, so a warranty on a joint covers the joint that was sealed, not a new path that opens three metres away. That is physics, and any contractor who will not say it in writing has not thought about it.

Six times we will tell you not to inject the joint

This section exists because it is the most useful part of the page. Every one of these is a scope we would decline or hand on, and each has a correct alternative.

• It is a designed movement joint. Sealant scope, backing rod, movement-capable sealant or a proprietary joint system.
• The joint is cracking along the line of reinforcement with rust staining, spalling or drummy concrete. That is corrosion driving the crack open, and injecting seals the problem in while the steel keeps expanding. Correct scope is concrete repair: break out to sound concrete behind the bar, treat or replace the steel, reinstate with a compatible repair mortar.
• Water is coming through the body of the slab or wall across a broad area rather than along the joint. There is no line to grip. The options are negative-side crystalline or cementitious tanking, a drained cavity system, curtain injection behind the wall, or excavation and a positive-side membrane.
• The deck above is ponding, the fall is wrong, or the surface joint sealant has failed. Injecting the soffit joint treats the symptom and the water simply finds the next weak point in the same joint. Fix the surface first, or price both together and say which is doing the work.
• The ag line, weep holes or stormwater serving the wall are blocked or absent. Sealing a retaining structure without restoring drainage raises the head against a wall that may not have been designed for saturated backfill. Clear the drainage first - sometimes that is the entire fix.
• The element is still moving. Diagonal cracking, cracking that widens toward the top, any lean, bulge or step. Fit tell-tales, read them over 4 to 12 weeks across a temperature and moisture cycle, and get the cause determined before anything is sealed. Injecting a moving joint is money spent twice.

What joint sealing costs, line by line

The rate band below is for the injection itself. Everything that gets a crew to the joint is priced separately and shown separately, because those lines are frequently larger than the injection, and burying them is how quotes stop being comparable.

Two structural facts about the pricing. Long continuous runs on one site drop toward the bottom of the band, because set-up, mobilisation and pump priming are amortised across the run. Short single-joint visits do not price against a rate at all - they price against the site attendance minimum, which is why a four metre joint and a fourteen metre joint can cost close to the same.

What it costs

Indicative only, and excluding GST. Build a line-by-line estimate for your own job with the price book, or read the working behind the rates in the 2026 cost guide.

Questions we actually get asked

How do I tell a construction joint from a crack when I am writing the scope?

A construction joint is straight, it usually runs the full length or height of the element, and it corresponds to a pour break, so it will often show on the construction drawings or as a colour and texture change in the concrete face. A crack wanders, changes width along its length, and does not respect the pour. It matters for the scope because a joint needs closer packer centres, more resin and a per-packer volume stop, and it carries a higher rate per linear metre. If the scope says crack injection and the defect is a 24 metre kicker joint, you will get quotes that are not comparable.

What packer spacing should the specification actually nominate?

Nominate a band and a test rather than a single figure. The practical field range for joints is 200 to 400 mm centres, with the rule that spacing should not exceed the element thickness and about half the element thickness being a safe default on critical work. Then make it empirical: require a water-flush connection test through every packer before injection, with resin observed at the adjacent packer during it. If resin will not travel from one packer to the next, the spacing was too wide, and that is a finding on day one instead of a callback in six months.

The joint on our drawings is marked as a movement joint, but it is leaking. What is the correct scope?

Joint replacement, not injection. Cut out the failed sealant back to sound faces, install the correct size backing rod so the sealant has the right shape factor and does not bond on three sides, and install a movement-capable sealant or a proprietary joint system rated for the movement the joint was designed to accommodate. If somebody has already injected it, expect to find cracking in the concrete beside the joint, because that is where the movement went.

Can a re-injectable hose be retrofitted to an existing joint, or is it new-build only?

It can be retrofitted, by chasing a groove along the joint line, fixing the hose and encapsulating it with injection and vent ends brought out to accessible points. It is worth doing where re-access will be expensive or impossible later: a joint about to be covered by a fit-out, a tank you cannot drain twice, a soffit that needs an elevated work platform each visit. On an accessible joint you can walk back to, drilled packers are cheaper and do the same job.

Why does one quote price the joint per linear metre and another prices it as a lump sum per crack?

Because there is no agreed unit in this trade, which is exactly why quotes for the same defect can differ by a factor of three. Normalise them before comparing. Ask each contractor for the linear metres of joint they have measured, the packer centres they will use, which resin they will use and why that one for this joint, and whether making good is in or out. Two of those four questions usually explain the whole difference.

How much resin should a joint take, and how do I know we are not being pumped full of foam we do not need?

Do not use the free-rise expansion figure on the product data sheet to estimate volume. Free rise of 8 to 30 times is an unconfined laboratory number; inside a confined joint under back pressure, real expansion is far lower, and field practice works on roughly 3 to 8 times. The control is a nominated volume stop per packer, in the order of one to two litres. If a packer takes far more than the stop, the joint has broken out into a void or a drainage layer and the answer is to stop and re-think, not to keep pumping.

Can this be done while the car park stays open?

Usually yes, in stages, with certified traffic management and only part of the deck closed at a time. What that means in practice is that traffic management and after-hours penalties become real line items, often larger than the injection itself, and that vehicles within reach of the work have to be protected. One resin drip on a bonnet costs more than a day of injection. We itemise those lines so the building owner can decide whether the disruption saving is worth the after-hours premium, rather than discovering it inside a lump sum.