Digging foundations - How to dig and fill porch footings

[MattRowe]

I am currently trying to figure out how to lay the foundations for a porch. The shape is a quater circle.

I am going to build the walls using 9" blocks, therefore the footings need to be 9"+4" as I understand it.

Do I just dig a trench a metre deep and 9"+4" wide, add shuttering to where the floor should start and fill it with readymix?

If I do this I will be left with a submerged conrete wall but I need a floor. I feel a bit dim but I have no idea how to create the porch flooring. Do I just fill the whole area (quater circle) with readymix? This would be 3 square metres?!

I am sure that I am doing something wrong but I am not sure what.

[Tony McC]

Using a 225mm block, the footing needs to be 225 + 100 +100 = 450mm (ish) - you need spread to either side of the blockwork.

The normal method would be to pour a strip footing, bring up the blockwork to floor level, then pour a separate oversite slab to create the floor. If you wanted to make it hard work, you can shutter off the internal floor and try to persuade the plastic concrete to remain at two different levels but gravity will probably win

[MattRowe]

Now it makes sense, I was thinking that you had to create a wood floor with joists etc and couldn't figure out how the joists would attatch to the foundation. Many thanks this makes things easy.