Concrete Decision Center

Work out what you are looking at, before anyone quotes you

Most concrete advice jumps straight from a photograph to a repair. This section does not. It separates what you can observe from what it might mean, what a professional would check, and what a contractor might propose — so that when you do ask for estimates, you can tell whether two of them describe the same job.

• I have one estimate and want to understand it

  Work through the proposal item by item and see what it states, what is unclear, and what to ask.

  Open the estimate decoder

• I have several quotes and want to compare the scope

  Put two or three side by side across every scope item. It shows where they differ; it does not pick one.

  Compare quotes by scope

• I am documenting a problem before contacting anybody

  Record what you have observed and print a summary to have in hand when somebody visits.

  Start a project record

• I do not know which repair approach applies

  Start from the symptom and read what each method does and does not resolve. Which one suits a property needs somebody on site.

  Repair or replace?

• Something changed and I do not know what

  Uncertainty is a legitimate starting point. Work out what to photograph and measure before anybody arrives.

  Start from what you can see

• Concrete slab

  Spreads the weight of people, vehicles and stored items across the ground beneath it, and gives a durable surface to walk or drive on.

  A slab's appearance says very little about what is under it. Sound-looking concrete can be spanning a void, and a cracked surface can be sitting on perfectly stable ground.

• Slab edge

  Terminates the slab. Unlike the middle, an edge is usually supported on one side only, which makes it the first place loss of support shows.

  Edge damage does not establish that the whole slab is failing. It frequently reports what the ground immediately beside the slab is doing, which can be a very local problem.

• Control joint

  Concrete shrinks as it cures and moves with temperature. A control joint gives that movement a planned place to relieve itself, so cracking happens in a straight line somebody chose rather than across the middle of the surface.

  A cracked control joint is not a defect — it is the joint doing its job. What it does not establish is whether anything beyond normal shrinkage is going on.

• Construction joint

  Marks where placing stopped and later restarted. The two sides are separate concrete placed at different times, which means the joint behaves differently from the slab either side of it.

  A visible construction joint is not evidence of poor work — most slabs of any size have them. It does not establish whether the two sides are connected.

• Expansion or isolation joint

  Keeps a slab from bearing directly on a wall, a step, a column or another slab, so that when one moves it does not transmit that movement into the other.

  A gap opening at an isolation joint does not establish that a building has moved. It commonly means the slab has, which is a different and usually much smaller problem.

• Subbase or base material

  Spreads load, gives a uniform surface to place concrete on, and provides a path for water to leave rather than collect under the slab.

  Nothing about a base can be established from the surface. Its depth, its material and how well it was compacted are invisible once concrete is over it.

• Subgrade soil

  Carries the load that the slab and base spread out. Its behaviour when wet, when dry and when disturbed governs most residential concrete movement.

  Nothing about subgrade can be established from a website, a map at regional scale, or the appearance of the concrete above it. Ground conditions change over very short distances.

• Reinforcement

  Concrete is strong in compression and weak in tension. Reinforcement carries tension, which mainly governs how cracks behave rather than whether they happen.

  Whether a slab is reinforced, with what, and where cannot be established by looking at the surface. Its absence is not automatically a defect, and its presence does not prevent cracking.

• Footing

  Takes concentrated load from a wall or column and distributes it over enough ground area for the soil to carry it.

  Cracking in a slab or a wall above does not establish anything about a footing. Footings are buried, and their condition is not visible from inside or outside a building.

• Foundation wall

  Holds back soil and any water pressure in it, while carrying load from the building down to the footing.

  A crack in a foundation wall does not establish its cause or its significance. Shrinkage cracking and movement cracking can look similar to an untrained eye.

• Stem wall

  Raises the structure clear of the ground and transfers load down to the footing, usually around the perimeter of a building.

  Surface damage on an exposed stem wall does not establish anything about what it is carrying. Weathering on the exposed face is common and often superficial.

• Pier or column support

  Takes load from a beam or a floor at one point and transfers it to a footing or the ground below.

  Cracking or spalling on a pier does not establish whether it remains adequate. Point supports carry concentrated load, which is exactly the condition an owner cannot assess by eye.

• Driveway apron

  Carries the heaviest and most repeated vehicle loading on a property, at the point where the ground beneath is most likely to have been disturbed during construction.

  A dropped apron does not establish that the whole driveway is failing, and it does not establish anything about the garage structure it meets.

• Sidewalk panel

  Provides a walking surface, sized so that individual panels can move slightly without cracking each other.

  A displaced panel does not establish who is responsible for it. Frontage responsibility is set locally and cannot be inferred from a property line.

• Patio slab

  Provides an outdoor living surface, and — whether or not anybody designed it that way — decides where a large volume of rainwater goes next to a building.

  Settlement of a patio does not establish that the adjacent building has moved. It is usually the opposite: the patio moved and the building did not.

• Garage floor

  Carries concentrated wheel loads, and usually sits over ground disturbed when the building's foundation was placed.

  Cracking or settlement in a garage floor does not establish anything about the foundation around it. In most construction the floor is not structurally connected to the walls.

• Basement floor

  Provides a finished floor and, in many constructions, sits above whatever drainage system was installed under the building.

  A crack in a basement floor does not establish a foundation problem. Basement slabs commonly crack from shrinkage, and they are usually not structural elements.

• Porch or stoop

  Provides a level landing at a doorway, usually raised above surrounding ground and frequently supported differently from the building it serves.

  A porch pulling away from a house does not establish that the house has moved. Porches are commonly supported on their own fill and settle independently.

• Concrete steps

  Carries pedestrian traffic between levels. Because people climb on a rhythm set by the first steps, consistency between risers matters as much as the condition of any one of them.

  Surface damage on steps does not establish that they are unsafe, and tidy-looking steps do not establish that they have not moved.

• Retaining wall

  Resists the pressure of retained soil. Because saturated soil pushes considerably harder than dry soil, a retaining wall is a water-management structure as much as an earth-retaining one.

  A retaining wall that looks sound does not establish that its drainage works. Failures typically begin behind the wall, where nothing is visible, long before the face shows anything.

• Pool deck

  Provides a walking surface around a pool and, at its inner edge, meets coping and the pool structure itself — which is what makes movement here less forgiving than movement elsewhere.

  Deck settlement does not establish that the pool shell has moved, and it does not establish that a leak exists. It also does not rule either out.

• Drainage path adjacent to concrete

  Determines whether water leaves a property or travels through the ground beneath its flatwork. It is not concrete, and it is the single most common reason concrete moves.

  A visible drainage problem does not establish that it caused a particular movement, and tidy drainage does not establish that water is not the cause.

• Joint sealant

  Bridges a joint so surface water runs across rather than into it, while remaining elastic enough to accommodate the movement the joint exists to allow.

  Failed sealant does not establish that anything structural is wrong. Sealants are consumable and have a service life shorter than the concrete around them.

• Surface coating or overlay

  Changes the surface a slab presents — its appearance, its resistance to staining or chemicals, sometimes its texture. It does not change what the slab is doing.

  A coating conceals the surface it covers. That means a coated slab tells an owner less about its own condition than an uncoated one, not more.

• Base or subgrade reconstruction

  Remove and rebuild the prepared layer beneath a slab so it has uniform support.

  Does not resolve: The water that removed the original material, unless drainage is also addressed

• Concrete resurfacing

  Place a new thin layer over existing concrete to give it a fresh surface.

  Does not resolve: Movement — a resurfaced slab that moves will crack through the new layer

• Crack sealing

  Keep water and debris out of a crack so the crack's edges do not deteriorate further.

  Does not resolve: Whatever caused the crack, if the cause is still active

• Demolition and removal

  Break up existing concrete and take it away.

  Does not resolve: Anything about the ground left behind, which may need work

• Drainage correction

  Change where water goes so it stops arriving at or beneath concrete.

  Does not resolve: Damage already done to concrete, which still needs its own repair

• Epoxy injection

  Fill a crack with a rigid resin intended to bond the two sides together.

  Does not resolve: Active movement — a rigid bond across a moving crack tends to crack again beside the repair

• Flexible joint sealing

  Restore a watertight but movable seal in a joint that is meant to move, so water runs across rather than into it.

  Does not resolve: Movement itself — the joint will still move, which is the point

• Foundation stabilization

  Restrain or support a foundation element that has moved or is judged likely to move.

  Does not resolve: Existing displacement, in most cases — stabilising is not straightening

• Full-depth repair

  Remove and replace concrete through its full thickness over a defined area.

  Does not resolve: The base or ground condition beneath, unless that is separately included

• Grinding

  Remove material from the high side of a displacement to eliminate a step.

  Does not resolve: The movement that created the step, which may continue

• Monitoring before selecting work

  Establish whether something is actually changing, and how fast, before committing to a scope of work.

  Does not resolve: Anything, immediately — this is a way of finding out, not a repair

• Overlay

  Place a substantial new layer of concrete over an existing slab, bonded or unbonded.

  Does not resolve: Movement in the slab below

• Partial-depth repair

  Remove concrete down to sound material over a defined area and rebuild it, without going through the slab.

  Does not resolve: Loss of support beneath the slab, since the repair does not reach it

• Piering or underpinning

  Transfer a structure's load to deeper, more competent ground.

  Does not resolve: Drainage or ground moisture conditions

• Polyurethane crack injection

  Fill a crack with a flexible material primarily to stop water passing through it.

  Does not resolve: Structural continuity across the crack

• Polyurethane foam lifting

  Inject expanding polymer foam beneath a settled slab to fill voids and raise it.

  Does not resolve: Surface deterioration on the slab being lifted

• Pressure grouting

  Inject material into ground beneath or beside a structure to fill voids or densify loose soil.

  Does not resolve: Water movement that created the condition

• Protective coating or sealer

  Apply a product to the surface to reduce what it absorbs or to change how it wears.

  Does not resolve: A surface that is still losing material — a coating over that fails with it

• Reinforcement repair

  Treat or replace corroded steel within concrete and rebuild the concrete around it.

  Does not resolve: Corrosion elsewhere in the element that has not yet shown at the surface

• Retaining-wall repair

  Restore or restrain a wall retaining ground, and usually the drainage behind it.

  Does not resolve: Loading behind the wall, if that is what changed

• Slab replacement

  Remove an entire slab and place a new one.

  Does not resolve: Drainage or ground conditions, unless those are separately in scope

• Slabjacking or mudjacking

  Pump a cementitious slurry beneath a settled slab to fill voids and raise it toward its original level.

  Does not resolve: Deterioration of the slab's surface, which lifting does not touch

• Surface patching

  Restore a small area of lost surface material to a similar profile.

  Does not resolve: Ongoing surface deterioration, if the exposure that caused it continues

• Void filling

  Fill a gap beneath a slab to restore support without necessarily raising the slab.

  Does not resolve: Elevation — filling supports the slab where it is, it does not raise it