Reactive soils, drainage and site classes around Bairnsdale

Why soil matters so much here

Concrete sits on soil, and soil moves. Clay swells when it gets wet and shrinks when it dries. Sand can wash out or loosen when disturbed. Around Bairnsdale we work on terrace loams, Mitchell River alluvium, reactive hill clays and lakeside sand, sometimes within a few kilometres of each other, so understanding the ground is part of every quote.

Site classifications

For house slabs and many sheds, a geotechnical engineer tests the soil and gives the site a class under AS 2870: class A for sand and rock with little movement, class S for slightly reactive clay, class M for moderately reactive, H1 and H2 for highly reactive, E for extremely reactive, and class P for problem sites such as soft fill, flood-prone ground or sites affected by trees. Higher classes mean deeper beams and more steel.

Reactive clays at Wy Yung and Eastwood

The rises north and south-east of town often have a sandy surface over heavy clay. These sites commonly come back as moderately or highly reactive. Driveways and paths there benefit from steel, careful joints and, most of all, good drainage.

River flats and flood overlays

The flats beside the Mitchell, toward Lucknow and around the morass are lower and wetter. Some properties sit within flood overlays that set floor levels and limit fill. The ground there can be soft, so excavation and base depth increase.

Lake sand

At Paynesville, Eagle Point, Raymond Island and parts of Metung, sandy soils drain well but loosen easily and can have a high water table. Compaction, edge support and vapour barriers matter more than on clay.

Drainage that protects concrete

Most movement problems trace back to water. Downpipes should connect to stormwater, not spill beside a slab. Garden beds should not be overwatered against a driveway edge. Falls should take water to grates, pits or the kerb. We plan drainage as part of the job.

Bairnsdale ground, East Gippsland weather and Shire rules

Bairnsdale sits on terraces above the Mitchell River just before it runs out into Lake King. The older streets on the higher terraces mostly stand on red-brown loam over clay, which holds a slab well once the soft topsoil is gone. Down on the river flats toward Lucknow, the Macleod Morass and the Mitchell's lower reaches, the soil turns to fine grey alluvial clay that stays wet after rain and has gone under in big floods. The rising country at Wy Yung, Eastwood and Granite Rock has duplex soils where a thin sandy top hides stiff, reactive clay, and the lakes towns of Paynesville, Eagle Point and Metung bring sand and a high water table. Summers are warm and dry with the odd scorching northerly, winter mornings can frost, and east coast lows can drop a month of rain in two days. A test hole goes in at every site visit, and we set the excavation, base, steel and curing to suit what comes out of it.

Inside your own fence line, a driveway, path or patio rarely needs a permit. Once the work leaves your title and runs over the verge, footpath or kerb, it requires consent from East Gippsland Shire Council, which looks after Bairnsdale, Paynesville, Lakes Entrance, Metung, Bruthen, Orbost and the surrounding districts. Access onto the Princes Highway or the Great Alpine Road is a state road and involves the Department of Transport and Planning as well. Flood overlays, bushfire attack level ratings, house slabs and larger sheds can bring a building surveyor and engineer into the job. Your quote spells out which of those applies.

What a Bairnsdale Concreting quote shows you

Our quotes are written up after we have stood on the site, and they break the work into the pieces you would want to question. You will see the area we measured, any demolition of old slabs, pavers, bitumen or gravel and where it will be tipped, how deep we plan to dig, the crushed rock we will bring in and how many compacted layers it goes down in, the concrete strength, how thick the slab will be, and the reinforcement plus the chairs that lift it, the surface finish or stone mix, the joint layout, pits and stormwater connections, edges, steps and sealer. A vehicle crossing permit from East Gippsland Shire, a concrete pump, a long wheelbarrow run behind a house, or protection for a neighbour's garden are each listed as their own line.

We do not publish rates per square metre. Around Bairnsdale a driveway can sit on free-draining red loam on the river terraces, on grey alluvial clay down on the Mitchell River flats, on heavy duplex clay up at Wy Yung, or on loose lake-edge sand at Paynesville, and those four sites need four different bases. A figure printed on a website would be wrong for most of them, so we look first and quote what your block actually needs.