Underpinning in Melbourne's Northern Suburbs — Brick & Brick Veneer

When underpinning is the right fix

A brick or brick-veneer house is not carried on stumps around its outside walls. It sits on a continuous concrete strip footing. If the ground under that strip softens, shrinks or washes out, part of the footing drops, and the brickwork above it cracks. Underpinning puts new, deeper support under the failed section so it stops moving.

Typical signs include:

• Stair-step cracking that follows the mortar lines in outside brickwork.
• Tapering cracks that are noticeably wider at one end, close to a corner of the house.
• Gaps opening between brickwork and window or door frames.
• Internal cracks over openings on the same wall as the external damage.
• A sticking front door on a brick house that has never given trouble before.

Not every crack in brickwork means underpinning. Fine shrinkage cracks, rusted lintels and thermal movement can all look alarming without the footing being at fault. That is why the first step is always an inspection and, where needed, an engineer's assessment.

Why brick homes in the north move

The suburbs from Coburg North and Reservoir up through Thomastown, Lalor and Craigieburn were mostly built on the basalt plains, where the topsoil is heavy, reactive clay. Many brick veneers from the 1950s to the 1970s were put on footings that would not meet the soil classification rules introduced later. They perform well for decades, then a run of dry summers, a big tree planted too close, or a leaking stormwater pipe tips one corner past its limit.

On the eastern side, around Ivanhoe, Heidelberg, Rosanna and Greensborough, the ground is more varied. Sloping blocks, cut-and-fill sites and pockets of softer silt near the Darebin Creek and Plenty River can cause settlement for different reasons. The repair method changes depending on which problem you have.

How we underpin

Underpinning is engineering work, not guesswork. The process normally runs like this:

• Assessment. The cracks are mapped and measured, internal floor levels read, and drainage, trees and plumbing near the affected wall looked at.
• Engineering. A structural engineer designs the repair: how deep, how wide and how far along the wall the new support needs to go.
• Permit. A building permit is lodged through a building surveyor.
• Excavation in bays. The footing is exposed in short sections, never all at once, so the wall is always supported by the ground either side of each bay.
• New concrete. Each bay is dug to the design depth, inspected, then filled with concrete under the existing footing and packed tight once cured.
• Making good. Soil is replaced, paths reinstated where practical and the cracks are left for a period before they are repaired.

For some sites the engineer may specify screw piles or bored piers instead of mass-concrete bays. We work to whatever the design calls for.

How long it takes

A single corner or one wall section can often be underpinned within a few days once the permit and engineering are in hand. Longer runs, deeper designs or rock in the excavation take more time. The concrete in each bay needs to cure before the next bay beside it is dug, which sets the pace more than anything else.

Fixing the cause as well

Underpinning a corner without dealing with what made it drop is a short-term fix. While the ground is open we look at:

• Stormwater and downpipes that discharge against the footing.
• Leaking sewer or water pipes under or beside the wall.
• Trees and large shrubs drawing moisture out of the clay.
• Garden beds and paving that hold water against the brickwork or shed it under the house.

Sometimes a plumbing repair and better drainage are enough to stop the movement, and underpinning is not needed at all. If that is all it needs, that is what we will say.

Brick veneer with stumps inside

A lot of northern suburbs brick veneers have brick outer walls on a strip footing and a timber floor inside carried on stumps. Those houses can need both kinds of work: underpinning on the perimeter and restumping on the internal stumps. We assess both together so the floor and the walls end up level with each other rather than fighting.

Getting started

Book a free inspection. We look at the cracking, take floor readings, and explain whether the problem looks like footing failure, plumbing, drainage or something else. If underpinning is needed, we arrange the engineer and give you a written quote.