Did landscaping and work DIY, Here's what I have to fix most...
I Did landscaping for about 5 years (patios, decking, fencing). Worked in DIY Retail store in the building department for around 2. Here the one thing I had to quote the most and Here's how I'd work out materials for a 4m x 3m patio (12m²):
Sub-base: 100mm MOT Type 1, about 2.4 to 2.8 tonnes (10% allowance for compaction)
Bedding: about 845kg sharp sand + 211kg cement (4:1 by weight, 40mm deep)
Mixing it yourself: about £150 vs £490.10 for premixed bags (my shelf prices, check yours)
And the thing most beginners skip: a cement priming coat on the back of every slab.
I've put this into a free calculator that does rectangles, L-shapes and circles. Would that be useful to anyone planning a patio?
This will work for any metric or pricing, just adjust to your local currency