[1STNewHomeOwner]

Hi all I have a 1.9 metre drop in elevation from my grade line on my home to the back alley and was wondering what the specs of lumber has to be tobuild a retaining wall, sections will still be 8 feet. What size posts and what thickness of planks do I have to use, and finally how far up towards my house do I have to keep the wall on the sides?

[cdnk5]

Tough to give an answer as it's a pretty vague description of your layout. That sounds like a pretty big wall though. Don't think you could go 1.9m in a single wall unless you're using concrete. More likely to do several steps to reduce the force acting on the wall. Also pretty sure you will need much closer spacing than 8ft. At my last house in Calgary I had about a 4ft drop from my garage off the back alley to the house and I did it in 2 steps and used 4x6 posts every 4 ft.

Best bet is to get an engineer who could give you the exact requirements to be safe.

[1STNewHomeOwner]

Thanks for the response I was planning on 6by6 posts 4 feet apart and keeping my fence sections 8 feet so the fence posts will be full lengths and the middle support posts will be 4 feet high and I think I need at least 3 anchor posts for the wall itself not sure. These would be cemented 6 feet into my lot and lag bolted to the support posts on the wall itself, still not sure how far to carry the wall on the sides towards the house.

[roadmanjim]

When I was growing up, we built many stone walls (New Hampshire). One of the lessons that I took away from that experience dealt with the issue of water. If there is not sufficient drainage behind the wall, it will become a dam and a cubic foot of water weighs a lot more than a cubic foot of soil. So, do your homework and take steps to allow ground water to escape from behind the wall.
Food for thought.

[jsnbrd]

roadmanjim hit the nail on the head hydrostatic pressure will tear down your castle any day. cdnk5 also mentioned an engineer. He is correct as well. You are creating two things here a liability issue for yourself and a water damn. You need reinforcing a correct wall thickness and mix design. You can go about it by contracting an engineer, for an engineer this is a small project. If you bargain with an engineer he may cut you a deal. Research the pressure of the area you plan to apply to your wall then an engineer can run a couple of calculations to provide you with an amount of reinforcing you'll need the mix design of the concrete and the thickness of your wall, not too mention water dispensation.
"The factor of safety against overturning may be defined as the moment of the resisting forces (reinforced concrete) divided by the moment of the overturning forces (soils and hydrostatic pressure), both with respect to the axis about which the wall would overturn." Jensen Chenoweth