Answers:
To ensure proper cold weather concrete pour, add warm or hot water to the concrete mix to prevent it from freezing. you can also use an accelerator to allow the concrete to set when it is being mixed. also, you must always ensure to use the right concrete grade and the right mix when setting concrete.
Inform the client that the existing floor has a weak sub floor and you recommend for him to change it, and the work guarantee only covers the work done.
on the joint where the ply and cement board connect, support joint with noggins to limit movement, apply flexible sealant/ adhesive to joint and use flexible adhesive and grout to fix tiles.
You can build a garage or outbuilding on your property without planning permission as long as it's of a reasonable size – no higher than 4 metres. do bear in mind, though, that outbuildings can not take up more than half of the land around the original property.