Retaining wall foundations

We are looking at building a retaining wall, as we are on a small budget we are considering doing it our selves. If this is too expensive I will look at clearing the soil and doing a decking area with stairs and a blocking the underside off.

Please bare with my I am still researching as I type this so I may update as I go on.

I have attached the Sketchup file and material list for anyone who want to have a look at them. I have a 10mm space between brick for cement.

I plan on using

• 215MM HOLLOW DENSE BLOCK 7N
  
• 8mm 1M rebar

Currently not in the plan

• Drainage pipe
• Gravel backfill
• Rest of the garden

The length of the wall will be 883cm with a height of about a meter. My main issue is foundations, I have read various forums and articles where the recommended depth is anywhere from 150mm to 1M. In my plan (to work out materials and get a Idea of the finished project) I went for 500mm.

Using this site it came up with 6.158 cubic meters of concrete required, at 300mm foundations it was 2.468 cubic meters.

I then used this site for working out how much I would need to buy. It appears to be a lot is required and will more than likely make this too expensive to go through with.

So getting to my first question... Is 500mm the right foundation? Or would you recommend a different depth?

EDIT: Question 2; If you are a builder how much would you charge for the foundations, wall, foundations and wall? This is just as a guide, if it looks like it will be too much for me I will look into a local builder. But haveing a price to begin with will help decide if this is a option

Thank you in advance

Images from Sketchup file also includes in attached files

 

The soil type is clay.

Do you have to infill the blocks without the rebar? On the sites I have looked at the wall is built without filling them.

I was going to use rebar for strength as I was thinking of putting the fence post into the blocks at the top.

The concrete calculations did not include anything for the bricks them-self, its is only the foundations.

 

Thank you I will make a new plan using these 7N dense blocks.

What about the foundations depth?

 

It is for our back garden, a curved wall may look odd and most likly out side of my abilities. Currently weighing up the option and price for a deck of a deck.

 

Thank you for the advice already given,

I'm probably going to go with decking the area and removing most of the soil under it. I have spent a little more time on details with in the model. The hazard area is a drainage manhole.

The support are on a anchor concreted in, this anchor is going to change as the load is too off center.

The boards at the concrete will be attached

I now have 3 questions, well 4 if you include should I create a thread in a different section?

1: Do I need noggins?

2: Jt Atkinson where I have priced up the materials from don't seem to have any wood size to support the deck frame except fence posts. Are these fit for this purpose or will I need to find another source for theses.

3: The footings are 600mm deep and the diameter is 150mm. The diameter is just a guess as I plan on asking a local carpet shop a couple of tubes to help set and don't know the diameter yet. But is the depth sufficient?