How do I work out how much sand and cement I will need for rendering 100 square metres

Hi Rebecca Multiply 100 by 0.020 - average - which will give you cubic metres. There will be about 1.8 tonnes per cu.m. You will need 36 x 25kg bags of cement and 3.6 tonnes of sharp sand to cover 100 sq.m. with an average of 20mm of render.

If it is going to be about half an inch to an inch thick, then it would be 100 square meters by 12-25mm. So that would be between 1.2t and 2.5t of material. The average bulk bag of sand is 850kg, but check when you order! Some put more in some put less in some will measure it for you to within a few kilos. Depending on the mix, you then add in the relevant amount of cement or other additives to bring you up to the amount you want. If you are unfamiliar with the job, aim for the higher amount as this will allow for spillage, etc. Depending on where you get your sand and cement from, the bulk bag of sand will be between £45-250. This is because a builder's merchants could deliver it loose and dump it on your door step or you could buy a 20-25kg bag one at a time. Cement can vary from £4-20 for similar reasons. You might buy the lot in one go and collect it in the back of your car, so buying in bulk and collecting, or you might go to your local DIY store and buy a little 5kg bag one at a time.