Who to hire for cracks in the walls

Short answer

For hairline cracks in plaster, a plasterer or a painter. For cracks that are wider than a few millimetres, stepping through brickwork, growing, or accompanied by doors and windows that have started sticking, a builder — and often a structural engineer before anyone repairs anything, because filling a moving crack simply hides it until it opens again.

Plan itThere is time to get more than one quote, which is where the money is.

When it is someone else

Calling the wrong trade costs an attendance fee to be told so. These are the cases where this problem belongs to someone other than a Builder.

  • a structural engineer

    the crack is stepping through brickwork, wider at one end, over a few millimetres, or growing. An engineer's report is the document that tells a builder what to do and tells an insurer why.

  • a plumber

    there is a leaking pipe or a blocked drain nearby. Water moving soil under footings is one of the most common causes of movement in Australian houses.

  • an arborist

    there is a large tree close to the affected corner. Trees drying out reactive clay is the other most common cause.

What to do before anyone arrives

  1. Measure the widest point of the crack and write the date next to it — in pencil, on the wall. Photographing a ruler against it monthly is the cheapest structural monitoring there is and it answers the only question that matters: is it moving?
  2. Check whether doors and windows in that part of the house still close properly.
  3. Look outside at the same location for a matching crack in the brickwork, and look at the ground: a downpipe discharging beside the footing, a leaking tap, a garden bed that is always wet.
  4. Note whether it appeared after a very dry or very wet season. Seasonal movement in reactive clay soils is normal and is the explanation more often than not.

What to ask when you book

  • Is this cosmetic or structural, and what is your evidence?
  • Should I get an engineer before any repair?
  • If it is moisture-driven, what has to change outside before the patch will hold?
  • Will the repair be visible — does the whole wall need painting to match?

What changes the price

No dollar figures here: this directory holds no price data and an invented range is worse than none. What follows is what makes one of these jobs cost more than the same job next door, which is the part you can actually use when comparing quotes.

  • Cosmetic patching versus structural rectification, which are separated by an order of magnitude.
  • Whether an engineer's report and possibly underpinning are required.
  • How much of the wall has to be redecorated to make the repair invisible.
  • Whether the cause is external and has to be fixed first.

What you can do yourself

Is this licensed work?

Structural building work is licensed in every state above a threshold, and a structural engineer is a registered professional separate from a builder. Cosmetic patching is not licensed work.

There is no national register. Search the licence number with the regulator for the state the work is happening in.

Licensing thresholds and certificate requirements differ by state and change with amending regulation, so this page describes the mechanism rather than quoting a figure. The regulator’s own page is the current answer.

Common questions

Who should I hire for cracks in the walls
For hairline cracks in plaster, a plasterer or a painter. For cracks that are wider than a few millimetres, stepping through brickwork, growing, or accompanied by doors and windows that have started sticking, a builder — and often a structural engineer before anyone repairs anything, because filling a moving crack simply hides it until it opens again.
When is a crack in a wall serious?
The signals that matter are width, direction and change. Wider than a few millimetres, stepping diagonally through mortar joints, wider at one end than the other, visible on both sides of the wall, or measurably growing — any of those justify an engineer. Fine hairline cracking that follows a plasterboard joint and has not changed in years is almost always cosmetic.
Do cracks mean the house is subsiding?
Usually not. Most Australian houses sit on reactive clay soils that swell when wet and shrink when dry, and the seasonal movement that produces is normal and expected. Subsidence is a specific and less common diagnosis, and it is made from measurements over time rather than from a single look.

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Who to hire for

General information about who does what, not advice about your specific job. Licensing, consumer law and council rules differ by state and change; the regulator for your state is the current source. More guides to hiring a tradesperson.