Ashby's Weather App

Ashby's Weather App

The Ashby's Weather app is now available. The weather app predicts the likelihood of Thermal and Plastic Cracking and encourages planning to prevent it, e.g. Sikafilm.


This is a smart-phone based weather forecasting application designed to give concrete placers and contractors an indication of the weather over a 7 day timeframe that will enable the user to assess the potential influence of the weather on the concrete being placed. It is using meteorological data that is used to generate standard forecasts and uses additional inputs for relative humidity and wind speed.

Users need to consider this application as an additional tool to be used when deciding whether to proceed with a concrete pour. As it is a forecast, things can change. It is not a guarantee that what is predicted will happen. Conversely, a good forecast may change to produce unfavorable conditions on site for all of the usual meteorological reasons, If the work is being done in an area with a specific microclimate then the weather app predictions may not apply.


Go to Your current location is automatically detected on smartphones with GPS functionality. If this is disabled or not available, you can get a forecast for anywhere in New Zealand by using the search box at the bottom of the page and typing in your location.

Once the location is identified and displayed, a description on the screen shows graphically the weather forecast for the next 7 days. Touch (or click) the day summary to get a detailed hourly description of the plastic cracking risk for that day. You can scroll across the screen to show all of the day in question.

On the right hand side above the daily forecast is an advisory for overnight thermal cracking.

If you are being advised of both plastic cracking and thermal cracking for the same day and subsequent evening, then the risk of overnight cracking is very high and you need to think about early entry saw cutting of the control joints.


You can ask a direct question about whatever particular weather event you have in mind. Instead of typing in a location, try asking if it will rain tomorrow, or how hot it will be at 3pm?

Example questions:

Will it rain tomorrow?How hot will it be at 3pm?How windy will it be in Wellington on Thursday?How cold will it be on Saturday morning?


If there are predictions of plastic cracking then ensure you have Sikafilm available and you know how to use it. The risk of thermal cracking will require precautions to protect the concrete from the cold. It may be wise to reschedule the pour if the conditions are unfavourable and can not be mitigated. Your current location is automatically detected. By using the search box at the bottom of the page, you can get a forecast for anywhere in the world. Touch (or click) the day summary to get a detailed hourly description for that day.


The calculations assume that the concrete has the capacity to bleed and then calculates evaporation rates on that assumption. Some mixes are low or no bleed in nature and therefore the plastic shrinkage predictions do not apply. Mixes that should not be used in conjunction with this phone app are concretes 40 MPa and over, together with concretes containing limestone fillers, microsilica, flyash and ground blast furnace slags.