We are taking a pic once a day (have the luxury of visiting daily) from 6 different angles. Putting them together into 6 cool slide shows. It also doubles as proof of works. You can go back and see exactly what was done each day from the outside.
Along with this, keep a diary of works noticed each day and weather conditions (heat and rain). Use this as evidence when your builder hits you with extensions to contract due to inclemant weather. Our builder has hit us up on no work days due to heat and rain and have not backed it up with BOM records which they are requiered to do. I have BOM records and heat days they have claimed, only reached 31 degrees. Rain days had no rain at all.
I believe heat days are over 35 dergrees. Heat and rain must cause a delay of more than 4 hours to be counted as a loss work day. The builder must also have record of what tradies were booked for that day.