House restumping on the Gold Coast

What restumping actually is

A large share of Gold Coast homes built before the 1980s sit on stumps rather than a slab. The floor frame, made up of bearers running one way and joists running across them, is carried on a grid of short posts set into the ground. Those posts are the stumps. Everything above them, the floor, the walls, the roof, depends on them staying plumb and staying put.

Restumping is the replacement of those stumps. It usually happens because the original ones were hardwood, and hardwood in Queensland soil has a working life. Moisture rots it from the base up. Termites find it. The timber shrinks, splits and eventually crushes under load. When enough of them go, the floor above starts to tell you about it.

The replacements are almost always precast concrete or galvanised steel. Both outlast timber by a wide margin and neither is food for termites.

Full restump or partial

Not every job replaces every stump. A partial restump deals with the failed ones and leaves the sound ones in place. It costs less today and it is a legitimate approach when the failures are genuinely localised, for example one corner where a downpipe has been discharging into the ground for years.

The argument for doing the lot is simple. The stumps you leave behind are the same age, the same material and in the same soil as the ones you are replacing. Setting up a restump is a large part of the cost, since the house has to be supported and lifted either way. Doing half the house now and the other half in five years means paying for that setup twice.

What a good contractor will do is show you the evidence rather than assert either position. If two thirds of the stumps sound solid to a probe and are still plumb, a partial makes sense. If a probe goes into a third of them and the rest are marginal, you are replacing them all eventually and the only question is when.

How the work runs

Inspection and floor levels

Before anything is quoted, someone needs to get under the house. Not glance in from the side, actually get under it with a light and a probe. Every stump gets checked for rot, splitting, termite damage, plumb and settlement. The bearers, joists and ant caps get checked at the same time, because those fail alongside the stumps and finding out about them halfway through is what turns a fixed quote into a variation.

Floor levels get taken through the house with a laser or a water level. This is the part people skip and it is the part that matters most. Levels tell you how far out the floor is, in which direction, and whether the movement is one corner dropping or the whole middle sagging. Those are different problems with different fixes.

Scope and quote

The quote should tell you how many stumps, what material, what depth, whether bearers or joists are being replaced, whether the floor is being brought back to level or simply made stable, what happens to plumbing and electrical under the house, and whether making good the inevitable plaster cracking is included. A quote that says "restump house, $X" is not a quote, it is a number.

Support and lift

Temporary supports go in under the bearers, usually hardwood cribbing stacks with hydraulic jacks on top. The house comes up in very small increments across many points at once. This is the part that separates careful work from expensive work. Lifting one area faster than another twists the frame, and the frame passes that twist straight into the plaster, the cornices, the tiles and the window glass.

Stumps out, stumps in

Old stumps are removed and new holes dug to the required depth. Depth matters more than most homeowners expect, particularly in the reactive clay through Nerang, Mudgeeraba and the hinterland. A stump founded too shallow in clay that swells and shrinks will move with the clay, which puts you back where you started. New stumps go in plumb, get concreted, and galvanised ant caps are fitted between the stump head and the bearer. The bearer is packed to the correct height and fixed down.

Lower, level, make good

The house comes down onto its new stumps and final levels are taken. Then there is the cleanup, which on a house that has been out of level for twenty years usually includes hairline cracking in cornices and around door frames. Doors and windows that have been sticking often need adjusting once the frames come back to square, and that is a good sign rather than a bad one.

What it means on the Gold Coast specifically

Two local factors drive most of the work here.

Soil. The hinterland and the western suburbs sit on a lot of reactive clay, which swells when wet and shrinks when dry. That cycle works stumps loose over decades. Nearer the coast and around the canal estates the ground is sandier and often filled, and poorly compacted fill consolidates unevenly. Neither is a defect, it is just what has to be designed for, and it is why hole depth is a real question rather than a formality.

Water and termites. Subtropical rainfall keeps subfloor soil damp for long stretches. Damp soil rots timber stumps and South East Queensland has among the heaviest termite pressure in the country. A timber stump sitting in wet ground is the simplest possible path into a house. If a probe goes into a stump easily, get a licensed pest inspector involved before assuming it is only rot.

Signs it is time

• Doors and windows that stick seasonally, free up, then stick again
• A floor you can see slope, or one where a ball rolls the same way in more than one room
• Bounce or spring underfoot, which often points at bearers and joists as well
• Gaps opening between skirting boards and the floor
• Diagonal cracking running out from the corners of door and window frames
• Stumps that take a screwdriver easily, lean, or have visibly sunk
• Mud tracks running up a stump, which is termite activity and needs a pest inspector
• A building and pest report that has flagged the subfloor

Before you sign

Restumping is licensed structural work. Two checks cost nothing and both matter.

Look the contractor up on the Queensland Building and Construction Commission licence register. You can search by name or licence number and see whether they hold a current licence and what class it is.

Confirm home warranty insurance. Most residential building work in Queensland valued at more than $3,300 including materials, labour and GST must be covered under the Queensland Home Warranty Scheme. The licensed contractor takes out the policy and pays the premium before work starts, and you should receive a Notice of Cover. Structural defect cover runs six years and six months from practical completion. If the contractor is not licensed, the scheme does not cover you at all.