Side Return Groundworks & French Drain Advice

[eon]

Hi everyone,

As part of the on going works at our victorian terrace I am removing a thick layer of concrete which was poured over the original paving tiles in the side return. It's roughly 75mm thick. It has bridged the original slate damp course and the air bricks.
Of course it's lead to damp and rotten joists all along the perimeter/kitchen wall! My aim is to get the suspended floor and this side return all back functioning properly.
Please see the drawing below. The existing waste/drain is in pink. This runs out to a shared private lane which is tarmac. (I need to dig this anyway to lay an electricity line out to our garage and garden beyond.)

I would really appreciate any advice or thoughts on the following points:

1. While I'm at it I want to build a french drain along the external wall pretty much where the existing drainage line is. This is to help ensure no future problems with damp in these walls. Where should I position the new drainage pipe to accommodate the french drain? Bearing in mind this also is the soil pipe, kitchen grey water and rain water. Is running along the centre of the side return the best position? I will probably dig right back and make a new connection to the manhole.
2. Due to lowering the external ground level I may need to install a step below the back door. Is this possible without causing a damp area below the door? If so whats the best approach to this with out interrupting the french drain?
3. I'm very comfortable with carpentry, roofing and brick work but ground works is newer to me so is there anything else I need to consider here?

Any observations or guidance is very welcome.
Thanks!

 

[MatthewC]

I think you are on the right lines; I had to do extensive work to get my house dry 14 years ago, and it all worked very well.

At my back door I have a large stone slab outside the back door as the step, which cantilevers over a gravel border. You could consider that and possibly narrowing the French drain a little at that point so that it works. (I didn't need a French drain there as the floor is well above the ground level.) Also (it's not totally clear in what you say), you do realise that the foul drain will need to be separate from the French drain pipe (which has holes in!)?

 

[eon]

Thanks for the response Matthew, great to hear yours worked out.
That's great idea about the stone slab. We are putting in stone lintels so this could match.

Yes I see now that I could have been clearer in my post! So my plan is to position the new foul drain running along the centre of the side return with the fowl, grey water and rain water branching into it. Then have the french drain along the wall. I haven't decided yet weather to use a pipe in it or just clean gravel and geotextile membrane topped with decorative stones. If I do use a perforated pipe my only option for draining the pipe is to connect into the foul drain as with this terrace all of the rain water, grey water and foul runs into the same system on our shared lane way. My main concern is stopping water pooling at the base of the brick work perhaps a slight angle/filet of mortar falling away from the house at the bottom of the french drain would help with this too.