What the Bureau is actually saying

Strip out the noise and it comes to this.

Both the ocean and the atmosphere are reading as a strong El Niño. Every model the Bureau surveys has the tropical Pacific warming further through spring, peaking in late spring or summer. Forecast values are heading above the warmest on record since reliable records began in 1950. Given how strong it already is, the event is expected to hang around into autumn 2027.

The Indian Ocean Dipole is neutral for now, with models suggesting a positive dipole could develop through spring. Positive dipole on top of El Niño usually means an even drier, hotter run for eastern Australia.

One honest caveat, and it comes from the Bureau itself. A strong signal in the Pacific does not automatically mean strong impacts here. Some weak events have hit us hard and some strong ones have passed quietly. The ENSO influence on rainfall also tends to ease off around early summer. So plan for hot and dry, but do not bet the business on a forecast.

Plan your program for heat. Price your risk for heat. Then hope you did not need to.

Your crew is the first problem

People ask every summer what temperature you can knock off at. There is no such number in NSW, and chasing one is the wrong question.

Under the Work Health and Safety Regulation 2017, a PCBU has to ensure so far as is reasonably practicable that workers in extreme heat can do their job without risk to health and safety. SafeWork NSW is clear that the regulation does not set a precise temperature at which work must stop, because the risk depends on humidity, radiant heat, wind, workload, clothing, PPE, how acclimatised the worker is and their own health.

Forty degrees in the shade laying tiles is a different risk to forty degrees in a roof space, in a trench, or in full harness on a metal roof.

So the legal test is not the thermometer. It is whether you assessed the risk and did something reasonable about it. What reasonable looks like:

• Reschedule the hot work. Early starts, split shifts, heavy physical tasks in the morning, indoor or shaded work in the afternoon
• Cool water on site, in the shade, close to where people are working. Not a warm bottle in the ute at the other end of the job
• A proper shaded break area, not the back of a trailer
• Rotate people through the hot tasks instead of leaving the same bloke in the roof all day
• Watch new starters and apprentices. Unacclimatised workers go down first
• Put heat into your SWMS for high risk construction work, with real controls, not a line saying "drink water"
• Train supervisors to spot the signs. Dizziness, confusion, cramps, someone who stops sweating. Heat related illness gets worse fast and it kills

Worth knowing: while the WHS Regulation sets no stop work temperature, plenty of enterprise agreements and some award conditions do set thresholds and inclement weather arrangements. If your job is covered by one, that instrument applies on top of your WHS duty. Read yours before December, not during the first 42 degree day.

There is a productivity side too. Heat drops concentration and slows people down. Your blokes will not tell you they are working at 70 per cent. They just are. Program for it.

Concrete is where it costs you money

This is the one that catches builders out, because the damage does not show up on the day.

AS 1379 requires concrete temperature at the point of delivery to sit between 5 and 35 degrees. Above 35 at delivery and you are entitled to knock the load back. Industry guidance is that once ambient gets above about 30 degrees, you take precautions, and hot dry wind makes it worse regardless of the air temperature.

What heat does to a pour:

• Faster hydration, so less working time between discharge and finishing
• Slump loss in the truck, which tempts blokes to add water at the chute. Adding water at the chute cuts your strength and your durability. If you need workability, ask for an admixture, not a hose
• Plastic shrinkage cracking while the surface dries faster than bleed water can rise. This is the map of fine cracks you see on a slab the next morning
• Concrete cured hot at early age ends up weaker at 28 days than the same mix cured at a sensible temperature
• Once it hardens, hot weather damage cannot be fixed. You grind, patch, argue or repour

Practical controls that work on a Western Sydney job in February:

• Book pours for early morning. Night pours on bigger jobs
• Talk to your supplier about chilled water or ice in the mix, and about a retarder
• Wet down subgrade, formwork and reo before the truck arrives. Dry timber and hot steel suck water straight out of the mix
• Windbreaks and shade. Wind does more damage than most people credit
• Have enough labour on the job to place and finish quickly. Do not order more than you can handle
• Cure immediately and keep curing. Seven days minimum
• Record the delivered temperature on the docket. If there is a dispute later, that docket is your evidence

Total fire bans stop your hot works

This one blindsides people. On a total fire ban day, general purpose hot works in the open are not allowed. That means welding, grinding, gas cutting or anything else throwing sparks or flame. All fire permits are suspended.

On the spot fines start at $2,200. Taken to court it can run to $5,500, or 12 months imprisonment, or both.

There is a standard exemption schedule issued by the RFS Commissioner each time a ban is declared, and it includes cutting, welding and grinding for urgent and essential construction or demolition work. It comes with conditions: the work must be managed so fire cannot escape, adequate firefighting gear on hand at the point of work, the area below cleared of combustible material if you are working above ground level, and notification to the local Fire Control Centre or fire authority. Check the gazetted exemptions on the day. Do not assume last season's version still applies, and do not assume your job counts as urgent and essential just because the program is tight.

Total fire bans usually get declared the afternoon before, and they run midnight to midnight. The practical answer is to stop treating this as a surprise. Check the RFS fire danger ratings when you do your program each week, and move the steel fixing and the grinding off the days that look bad.

Remember the Bush Fire Danger Period in rural fire districts runs 1 October to 31 March, and can start earlier when conditions warrant.

Dry ground cracks houses, and the claim lands on you

Here is the sleeper issue for residential builders, and the one that turns up as a complaint eighteen months after handover.

Large parts of Western Sydney sit on reactive clay. Clay shrinks when it dries out and swells when it gets wet. That movement is what AS 2870 site classifications are about, and it is why footing systems on an M, H1, H2 or E site are designed the way they are.

A long hot dry run does a few things at once. The ground under and around the slab dries and shrinks. Trees and shrubs pull even more moisture out looking for water. Owners run water restrictions and stop watering garden beds against the house. The soil moisture goes uneven, and uneven is the killer, because differential movement is what cracks brickwork and racks door frames, not uniform movement.

Then it rains properly and the clay swells back. That is when the cracking really shows.

What this means for you:

• Get the site classification right and do not accept a stale report. A geotech investigation done in a wet year on a site that has since dried out may not reflect what is there now
• Watch your site drainage detailing. Falls away from the building, downpipes connected and discharged properly, no ponding against the slab edge
• Think about tree location and future planting near footings
• Hand over foundation maintenance information to your clients and keep proof you did. Most owners have never been told that they have a role in keeping soil moisture around their house even. If you never told them, the argument that they caused it is a lot harder to run
• Photograph and document the site at handover

Statutory warranty periods in NSW run for years past handover. Drought driven movement is exactly the sort of defect that turns into a Fair Trading complaint or a Tribunal matter long after you have moved on.

Water restrictions and dust

Dry seasons bring water restrictions, and restrictions hit sites in ways people do not plan for. Dust suppression on earthworks. Moisture conditioning for compaction, where you cannot hit density without water. Concrete washout. Wheel wash on the site entry. Curing water.

On top of that, dry and windy means dust complaints, and dust complaints mean council on your doorstep. Your erosion and sediment control plan was probably written with rain in mind. In a dry windy summer the bigger risk is airborne, not waterborne, and the controls are different: stabilise exposed areas, stage your earthworks so you are not opening up more ground than you need, keep haul routes damp, and get vegetation or cover down early.

Then the first big storm hits a bone dry stripped site and everything moves at once. Dry ground sheds water instead of soaking it up, so the runoff is worse, not better. Keep your sediment controls in place even when it has not rained in eight weeks.

Materials and trades that do not like heat

• Membranes and waterproofing. Check the product data sheet for maximum substrate and ambient application temperatures. A slab at 55 degrees in the sun is outside a lot of specifications, and a failed membrane is the most expensive callback in residential building
• Adhesives, sealants and renders. Skin over too fast, poor bond, cracking. Same answer: read the data sheet, shift to the cool part of the day
• Paint. Dries before it levels, leaving lap marks and poor film build
• Timber. Moves in low humidity. Doors, floors, joinery and trim that go in during a dry spell will move again when the humidity comes back
• Asphalt and roadworks. Placement temperature windows either side
• Plant and tools. Machinery overheats, hydraulic hoses fail, batteries die faster, and tyres on bitumen are a fire risk on high danger days

What it does to your program and your contract

Here is the part most builders never get straight until they are in a dispute.

Most standard building contracts have an inclement weather or delay provision, and most of them were written with rain in mind. Read yours and answer three questions before summer:

1. Does extreme heat, or a day lost to a total fire ban, actually fall inside your definition of inclement weather or a qualifying delay event?
2. Is it a claimable extension of time, and is it a cost claim or time only?
3. What notice do you have to give, and how quickly? Most extension of time clauses have a short notice period and they are enforced strictly. Miss the notice and you lose the entitlement even when the delay was real

If heat and fire ban days are not covered in your contract, that is a drafting job to do now, not in January. And keep a daily site diary with temperatures, fire ban declarations and what work was affected. Without records you have a feeling, not a claim.

The flip side is worth saying. Fewer rain days means fewer washouts, better access on clay sites, and earthworks that actually run to plan. A hot dry summer can be a good building summer if you shift your hours and manage the heat. The builders who get hurt are the ones who try to run a February program on October assumptions.

Bushfire and building approvals

Bad fire seasons have a long tail on the industry. More land gets mapped as bushfire prone. More jobs need a bushfire assessment and construction to AS 3959 with a BAL rating, which adds cost through shutters, screening, glazing, decking and cladding selections. Approvals take longer where the Rural Fire Service has to be consulted.

If you build on the fringe, get across Planning for Bush Fire Protection and the BAL construction requirements properly, because the cost difference between BAL 12.5 and BAL 40 is not small and you do not want to find it after you have priced the job.

The short version

• Move your start times and your pours now, not in January
• Write heat into your SWMS and make sure supervisors know the warning signs
• Talk to your concrete supplier about hot weather mixes before your first big pour
• Check the fire danger rating every week when you plan, and know the hot works exemption conditions
• Get your site classifications and drainage detailing right, and hand over foundation maintenance advice in writing
• Read your contract's delay clause and check whether heat and fire bans are even in it
• Keep a daily diary. Temperature, conditions, what stopped and why

Frequently asked questions

Is there a legal maximum temperature to stop work in NSW?

No. The Work Health and Safety Regulation 2017 does not set a temperature at which work must stop, because the risk depends on humidity, radiant heat, workload, PPE and the individual worker. The duty is to manage the risk so far as is reasonably practicable. Some enterprise agreements and award conditions do set thresholds, and those apply on top of the WHS duty.

What temperature is too hot to pour concrete in Australia?

AS 1379 requires concrete at the point of delivery to be between 5 and 35 degrees, so anything above 35 at delivery can be rejected. Industry guidance is to take precautions once ambient temperature is above about 30 degrees, and sooner if there is hot dry wind.

Can I use an angle grinder on a total fire ban day?

Not in the open as general purpose hot work. The RFS Commissioner issues a schedule of standard exemptions each time a ban is declared, and it includes cutting, welding and grinding for urgent and essential construction or demolition, subject to conditions including firefighting equipment on hand, clearing combustible material below the work and notifying the relevant fire authority. Check the gazetted exemptions on the day.

Does drought cause cracking in houses?

It can. Reactive clay soils shrink as they dry and swell as they take up water again. Uneven drying, often made worse by trees and by owners stopping watering under restrictions, causes differential movement under footings, which shows up as cracked brickwork and sticking doors. Site classification under AS 2870, good drainage detailing and giving owners written foundation maintenance advice are the main defences.

Can I claim an extension of time for extreme heat?

It depends entirely on your contract. Many inclement weather clauses were drafted with rain in mind and may not clearly cover heat or a fire ban day. Check the definition, check whether it is time only or time and cost, and check the notice period, which is usually short and strictly enforced.