Retaining wall foundations and french drain beside each other?

[Minyarra]

Hi folks,

I need some help. We live on acreage and recently dug out along a bank near our home to create a courtyard and utility zone. 

I need to put up a retaining wall of about 800mm high, which I am using the lintels with 75mm thick sleepers. I need to dig in some foundations which will be at least 400mm deep for the posts, but I also need drainage near here. That last storm turned the zone into a big muddy pond. 

I will get an excavator in to tidy it up and ensure it is sloping away from the home, which is toward the retaining wall.

My question is; how close can I put a french drain to the foundations  of the retaining wall and not undermine them?

[Minyarra]

thanks @MitchellMc , I will send photos to the store for comment. maybe the 're-enforcement' comment could be added to a A5 on how to install retaining walls along with @Dave-1 comment about ensuring wiggle room, unless those comments are there already and I just didnt read them 😞

[Dave-1]

Good Morning @Minyarra 

This is the difference between never having installed a retaining wall and having done some, to a few, to lots

You are now on the path The spacing of the posts I do think is in the manufactures specs, the warping ive seen smaller instances but not as bannanaish as yours 😕  

My "spacing rule" is something I was taught in reference to my Grandfather After he had passed my Grandma would always remind us that the fence rail spans were too long as it saved him and his mates from digging extra holes, they shot her down (imagines 1950's stirring) and then afterwards all the rails sagged By here telling me that story when I was ten (I am 50++ now) it really set in my head what happens to "spans" You now have the equivilent  

The re-enforcing sounds like a good inbetween option. And even switching the bannanas around so teh top row only bows in across the run could work. I would definently re-enforce with a vertical piece of timbe across each span (in the middle) tho.

Dave

[MitchellMc]

Hi @Minyarra,

As @Dave-1 mentioned, it's likely that the supplier has documentation covering the spans of their sleepers. In this guide on How to build a retaining wall, even a low non-structural wall requires "Every 2.4m or 3m sleeper must have posts at either end and one in the centre.".

Also, note that a retaining wall 1300 mm high would likely require engineering in most areas and council approval. The engineer would have picked up the missing middle post. With larger walls, there are a whole heap of different requirements, such as construction, footer size, drainage, etc., that need to be taken into consideration. That's why DIY walls typically stop at below the 1000mm mark.

With the addition of a brace timber behind the wall and long landscape screws, you should hopefully be able to pull those sleepers back into shape.

Mitchell