Sleeper retaining wall

[r44flyer]

Hello all,

I've agreed to do a garden makeover for some friends of ours. Their neighbour's garden is higher than theirs and the boundary is defined by a large, now nearly dead hedge (neighbour's responsibility). This hedge will come out at some point in the future to be replaced by a fence, but this would be right at the top of the small slope between the gardens. When the roots of the hedge are removed all the soil is going to be disturbed meaning a poor foundation for any fence.

My thinking so far is that a retaining wall will be needed to provide support for the fence foundations, help allow a more definite boundary and maximise lawn and planting space. The wall will be perhaps 700 high, and reduces down the length of the garden to perhaps 200. They like the idea of sleepers, being natural wood etc, and I agree, but I'm worried about longevity.

What sort of lifespan can I realistically expect from sleepers before they are significantly rotten to warrant replacement?

What can I do to stop the rot, if anything?

Will using oak be worth the extra expense over softwood?

Is it best not to bother and go for block and brick?!

Thanks again for your advice.

Jim

[lutonlagerlout]

oak is obviously the best wood, but for 700 high I would go for H blocks
LLL

[r44flyer]

Would there be any issues drilling an H block wall so I can clad it with a thinner sleeper?

[gonchy]

if you do go down the the oak sleeper route a local bm to me sells them at £22 8x4/2.6 and there good quality too not sure how fare they deliver cheaper than softwood and out last them too found there ebay add

http://www.ebay.co.uk/itm....e0b6016

[r44flyer]

Thanks gonchy. I can get them local to me (Brum) for £22 also.

[exoticpete]

Watch out using oak sleepers a lot of the 'Oak' sleepers are 'turkey' oak which does not last long and splits and cracks badly

[r896neo]

Any sort of fill behind a retaining wall is going to be crap for a fence post. I had a job like this recently and used 3m concrete posts dug into the original earth behind the wall.

It will last for a long long time.

The 3m posts were bloody heavy though...

I have roughly worked out from a few jobs that sleepers are around half the total cost of a masonary wall but obviously won't last more than 15 years. Probably look good for 6/7 ok for 10 and hang together til 15 or maybe a lot more if you back fill meticulously

[r44flyer]

Thanks for that advice. If the posts need to go in that deep, so be it. That will be the responsibility of the contractor the neighbour employs to do the fence. They might ask me to do it I suppose, so a deep post is what I'll suggest.

Can I assume the only realistic way to do that is with digger and auger?

[r896neo]

No what i'm trying to say is that you should do the posts at the same time as building the wall. You need to excavate back from the rear face of the wall by at least 6 inches anyway for drainage back fill so its easiest to dig them in now and if you put in concrete boys they won't need done again until past when you've retired.

[r44flyer]

I see, and good idea. It will mean convincing the neighbour to pay up for the job to be done at the same time but that's another matter.

If I buried gravel boards to the bottom of these long posts are they strong enough to act as a retaining wall? meaning any wall made of sleepers in front would be largely decorative. It would reinforce the gravel boards to a certain extent as the sleepers and fill behind them would add mass but not be the only line of defence. I don't want it to fail but don't want to waste material over-engineering what is still only 700mm at its highest point.