Uneven concrete

Telling the two apart

Settlement usually leaves evidence: a step at a joint where two panels have parted company, a gap where the slab has pulled away from a step or wall, cracks that have opened along the low side, or a slab that has tilted rather than dropped evenly.

An original pour problem tends to be smooth and continuous. There is no step, no gap, no cracking pattern that follows the low area — the surface simply runs the wrong way. Water pooling in the middle of an otherwise undamaged patio, with no sign of movement anywhere, often points this way.

What each one needs

Settlement can often be lifted, provided the slab is sound. That is the straightforward case.

A pour that was never right is harder. Options narrow to replacing the affected area, or building the surface up with an overlay or self-levelling material where the depth involved is small and the setting is interior or protected. Neither is a cheap correction to a cheap mistake.

Where unevenness matters most

At doorways and thresholds, where a change in height affects how a door swings and where water goes. At the top and bottom of steps, where uneven risers are a genuine fall risk. Anywhere water now runs toward the house rather than away from it.

On an open patio, a quarter of an inch of unevenness is cosmetic. At the top of a flight of steps it is not.

Measuring it before you call anyone

Ten minutes with a straight edge turns a vague complaint into something a contractor can quote against. Lay a long level or a straight board across the affected area and measure the gap under it at the worst point. Do the same across the joint where two sections meet, and note which side is high.

Photograph the level in place with the measurement visible. It sounds fussy, and it is the single most useful thing you can hand somebody who has not seen the property, particularly if you are collecting more than one opinion and want them working from the same facts.

Also check whether the surface runs away from the building or back toward it. A bucket of water poured at the high point will show you in seconds, and which way it goes changes the priority more than the size of the difference does.

What to ask a contractor

• Do you think this settled, or was it poured this way?
• What evidence are you using to decide that?
• If it settled, is the slab a lifting candidate?
• If it was poured this way, what are the realistic options and what do they each cost?

Common questions