Hidden retaining wall

[andrew223]

hi all

I have recently had a new fence installed and the next plan is to level out the garden which will mean raising the drop by around 600mm. The fence is 8.8m long. I cannot decide which would be the best way to retain the garden. It won't be seen as its against my fence and the other side will be under 2ft of soil!

See image

http://postimg.org/image/ud14hzfa1/

first option I was considering was compacting the soil with a roller and putting down 200mm of gravel and laying 200x100x2.4m new treated sleepers rebared and screwed together brick style. This would be 6 sleepers high. Membrane and gravel behind and drainage pipe. Cost on the sleepers alone seems to be coming out around £450 for 30 or so.

2nd option I looked at is the same sleepers chopped in half to 1.2m and buried 40% in dry mix concrete. Rest following above. Cost seems to about the same but I have a number of trees so it could be very hard work!

3rd option I considered 200mm medium density blocks laid on there side on a 300mm gravel base. Seems to be cheaper but not sure it would take the weight?

Basically I am looking for something cheap that will last and it doesn't matter what it looks like as I won't see it. Any ideas?

 

[Himaginn]

Personally, I think all three of your ideas are pants. To my mind you've gone ar$e about face on this.
You should have done the retaining wall, then the fence. Retaining walls are more important for their engineering design than they are for their aesthetics.

Your proposals provide nil provision against the walls sliding or overturning.
I appreciate you want a cheap and quick solution, but you might as well throw your money away. Whether your proposal may provide any danger to unsuspecting persons, I'm not sufficiently knowledgeable or aware of the situation to provide an opinion.

I'm not a pro, but I can imagine why the pros have not yet responded. You need whole design advice.
I respectfully suggest that you have a rethink and research more about retaining walls. It is a perfectly possible DIY project, but it should not be a quick, cheap, nasty solution.

You can still do a retaining wall without removing the fence first, but you'll need to build the wall in from the fence sufficiently to allow for the foundation to not interfere with the fence posts. This will allow possible renewal/replacement of the posts in the future without disturbing the retaining wall.
Or you could remove the fence, build a retaining wall and build the fence on or in conjunction with the wall.

 

[andrew223]

Hi thanks for your reply. The cheap comment is more aimed at i dont need it to look pretty as it wont be seen. Doing further research people using sleepers look to put in b bars out of sleepers buried into the soil to help against rotation.

Im open to ideas from scratch. Main thing its done properly.

 

[Himaginn]

What are b bars?

 

[andrew223]

Rebar with deadmen buried.

 

[r896neo]

Whats happening to the trees? They will almost certainly die if you simply bury the bottom 2 feet of the trunks?

600mm is not a great height to retain so i wouldnt be too worried about it. A 9'' block wall would be fine provided the drainage is done properly, but digging footings will be a big challange with the trees and if not done well to a good depth its at risk of failing due to roots affecting footings.

Sleepers would do screwed into posts concreted into the ground and because you wont see the back install posts very close to the fence but not touching, the wall should be a seperate entity.

Other choice would be dry stack mortar-less walls which would deal with the potential tree root movement better. Some of the civil engineering type ones are more brutal looking but very fast to build.

 

[andrew223]

The trees need to stay put so i will take that on board and redesign around them. There in 2 clusters so it should be possible. The current other side near the house is retaining just with 4inch treated posts sunk in the ground. I did consider doing this again 1.8m long with 50% in the ground.

The comment on posts sunk how deep would these need to be? Would a 100x200 sleeper 1.2m long sink 50% be enough if i put them every 2m? Would this also mean i could then stand them on the smaller 100mm side or would they still need to be on the 200mm thick side?

The motarless dry stack i did consider but couldnt find anyone in the uk? Do you have a link to the civil engineer type you mention?

 

[r896neo]

Concrete in posts/ sleepers about 18''-24'' deep. You want a post every 1.2m (assuming your sleepers are 2.4m length) to line up with the joints in your sleepers which should be laid in a stretcher bond like bricks with staggered joins.

I would happily use the smaller face of the sleeper as your post. The whole thing will last longer if you can have the posts out in the air beside the fence rather than buried behind the wall.
You may be able to bury the trees about a foot as they are mature-ish but 2 feet might kill them.

Tobermore make secura retaining walls but you'll only get their stuff in northern eng and scotland i think.