Concreting FAQs, Sunshine Coast

A handful of things, and none of them can be judged from your kitchen table. The first is the area in square metres, since a bigger pour uses more material and more labour. The second is the finish: plain concrete is the simplest, while exposed aggregate, coloured and polished finishes add process and cost more. The third is what is already there, because breaking out an old slab, carting the rubble away and excavating a proper base all take time before a single wheelbarrow of new concrete arrives. The fourth is access, which on the Coast can swing a job's price a long way, and the last is the ground itself. That is why every job needs a site visit. Ring us with your suburb and roughly what you want done and we will get a local concreter to come and price it properly rather than throw you a number that changes the moment they turn up.

Both are common on the Coast and both matter. Plenty of blocks around Buderim, Nambour, Montville and the Blackall Range are steep, which changes how the concrete gets from the truck to the formwork. If a truck can back up and chute straight in, that is the quickest and cheapest way. If it cannot, the mix has to be pumped or barrowed, which means more people and more hours. A steep site can also need extra formwork, steps or a stepped pour, and better thought given to where the water runs. Sandy blocks down on the coastal strip and around the beaches are a different problem: loose coastal sand has to be compacted properly and sometimes needs extra base material so the slab has something solid to sit on. A concreter who works your area already knows which of these applies before they arrive.

It can, and it is the single biggest thing that separates coastal concreting from inland work. Homes close to the beach or the water sit in a marine environment, and salt-laden air is what drives rust in the steel reinforcement and surface spalling, the flaking and pitting you see on older slabs near the water. The steel expands as it rusts and pushes the concrete off from the inside. The fix is not exotic. It comes down to the right mix, enough concrete cover over the reinforcement so the salt has further to travel before it reaches the steel, and sealing where it makes sense. None of that is expensive to build in at pour time, but it is very expensive to retrofit once the damage has started. A concreter who works the coastal suburbs will allow for it without being asked.

For anywhere that gets wet feet and salt, exposed aggregate is the finish most people land on. Washing back the surface to reveal the stone gives grip underfoot, which matters around pools, paths and beach-house entries where people walk through in bare wet feet. It also hides marks, leaf stain and general wear far better than a smooth grey slab, and it copes well with the coastal setting. Plain concrete still does the job and costs less, and coloured or stencil finishes sit in between. Whichever finish you choose, the durability near the water comes from what is under the surface, the cover over the steel and the mix, not from the look on top. Talk to the concreter about both.

Sealing is not compulsory but it earns its keep on the Coast, particularly on decorative and exposed aggregate finishes and anywhere near the water. A sealer slows staining from oil, leaves and general traffic, keeps colour from fading as fast, and adds a barrier against the salt air that ages coastal concrete. It is not permanent. It wears off over time and needs redoing periodically, and how often depends on the product used, how much sun and traffic the area cops, and how close you are to the water. Ask your concreter what they have put down, because the product determines the reseal interval, and there is no single answer that fits every job.

The slab sitting on your own land generally does not need approval, but the part where your driveway crosses the footpath and nature strip to meet the road, the vehicular crossing, does need approval from Sunshine Coast Council (or Noosa Council in the Noosa Shire, which is a separate council), and the council has its own specifications for how it is built. That covers the width, the profile, the materials and how it ties into the kerb. Stormwater and drainage can also come into it on some blocks, especially on the low river flats and canal estates near the Maroochy River, the Mooloolah River and Pelican Waters where water has to go somewhere sensible. A concreter who works the Coast will usually know the local requirements and how to arrange the crossing, but the approval itself sits with the Council, so it is worth raising early rather than after the pour.

Walking is usually fine within a day or so, once the surface has hardened enough not to mark. Driving is a different matter. You should generally keep cars off a new driveway for about a week, and heavier vehicles such as trucks, caravans or a loaded trailer for longer again. Concrete keeps gaining strength for weeks after it looks finished, so the surface being hard underfoot does not mean it is ready to carry a car. Your concreter will give you a specific time based on the mix, the thickness and the weather on the day. In the cooler months the reaction that hardens concrete runs slower, so a winter pour on the Coast will sit at the longer end.

Winter is fine, it just moves more slowly. Cold slows the chemical reaction that hardens concrete, so curing takes longer and the concreter may adjust the mix or the finishing schedule to suit. Rain is the bigger problem, and the Coast gets its share of it. Water landing on a fresh surface before it has set can weaken and mark the finish, so pours get postponed when the forecast is poor. It is frustrating to have a job pushed back a few days, but a concreter who reschedules you because of rain is doing right by your slab. Trying to pour through a downpour to keep to a date is how you end up with a surface that never looks right.

All concrete cracks to some degree. It shrinks as it cures and it moves with temperature and ground conditions, and it has very little ability to stretch. The job of a good concreter is not to stop cracking outright, which cannot be done, but to control where it happens using control joints, correct steel and a properly compacted base. Fine hairline cracks are normal and cosmetic and are nothing to lose sleep over. What is worth a look is a wide crack, a crack with a step or height difference across it, or a crack that keeps growing, because those usually point to something moving underneath, poor base prep, or drainage that has failed. If you are seeing that, get someone to look at it rather than filling it and hoping.

It depends entirely on what is going on top of it. A residential driveway carrying cars is typically around 100mm with reinforcing mesh through it. Anything carrying heavier loads, a truck, a caravan, a boat trailer or an industrial hardstand, needs more thickness and heavier reinforcement. Ground conditions change it too. The reactive clay and basalt soils through the Blackall Range hinterland can call for a different approach than a stable sandy pad closer to the water. Your concreter should specify the thickness and steel for your particular job rather than pouring a default, and it is a perfectly fair question to ask when they quote you.

Often, yes. If the existing slab is structurally sound, not badly cracked and has not dropped or moved, resurfacing is usually cheaper and faster than demolition and a fresh pour, and it saves you the mess of breaking the old one out. If the slab has deep cracks, a step across a crack, or drainage that has failed, an overlay just puts a new surface over the same problem and it will come back through within a season or two. Someone needs to stand on it and look at it to tell you honestly which situation you are in. It is one of those calls that cannot be made from a photo.

The whole region. That runs from Maroochydore and Buderim through the coastal strip at Mooloolaba, Kawana Waters and Golden Beach, north to the beaches at Coolum Beach, Peregian and Mudjimba, south to Caloundra, Kings Beach and Golden Beach, and inland to Nambour, Sippy Downs and Beerwah. Our suburbs page lists everywhere we work in detail.