Timber Retaining wall construction help please!

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dougens

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Timber Retaining wall construction help please!
« on: May 01, 2013, 23:07 »
Hello

I bought a terraced house and have a small plot of steep land out the back of the house.
I would like to build a one step retaining timber wall to plant my vegetables in and need some help.

The layout is a pretty steep with a breeze block wall at the foot of the hill and a fence at the top.  There is a smaller bed held on the top left hand corner above a raised concrete plinth. Please see attached picture for layout.  The width of the plot is roughly 2-2.5m wide by 3-3.5m deep (or high!)

I plan to build a retaining wall half way up (or more or less) the main plot on the right and leave the smaller plot on the top left as a smaller bed.  The idea being to use the three plots, two larger and one smaller for rotation etc.

I've had advice from a local friend of mine on building the retaining wall and his instructions are this:
It is worth noting I'm not going to spend alot of money on this and I was quoted £1500 for the work and materials.  I have been quoted for the materials I need as per following instructions at roughly £200-300 and that's fine by me.

Dig a trench the width of the sleepers and below them on the hill dig out 4/5 holes for my pegs or stakes to go in.  Use postcrete to set these posts and fix the sleepers behind the posts and attach with galvanised nails.  Move the soil from the lower level and place on the higher level.  the bottom level will be roughly level and in line with the breeze block wall whereas the top level will be more of a slight upward slope as I'm wary of digging into the slope too much with the top fence there.

I do not know the quality of the undersoil but will find out more as I dig down to fix the supporting posts.  I'm not going to spend a fortune on sorting out the soil and re-laying etc)
I plan on using 47x50x1000mm posts (thinner than usual 4"x4" - hence using 4/5 posts rather than three, which the neighbour has!)  and sleepers the width of the plot x 200mm high and 47mm deep.  All timber used will be treated.


I'm not sure how far in the ground my pegs need to be for fixing so am not using the standard 600mm high posts as would rather get as far into the earth as possible. 

I know to seasoned landscapers this may sound a bit unplanned and haphazard so please let me know if this is the case and advise.

I'm not one for the polished look and more down with if it works and serves it's purpose great.
Regarding getting soil in and out of the plot it is a nightmare as everything has to go through the house so the less of this the better.  Hence using the soil from the bottom level for the top level as much as possible and fill the rest in with sacks of soil. 

When I bought the house there was turf on the slope and I have removed this but want to make sure I kill all roots etc so prior to doing the work I plan on rotivating the whole plot and was told best option is the to use rootkiller solution (roundup).  Can anyone advise on this?


Does this sound like I'm on the right lines for the construction?
Finally, should I be digging out the bottom level flat first and getting as much soil up top or wait till I've made the structure then move up?

Many thanks for any replies in advance.






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« Last Edit: May 01, 2013, 23:16 by dougens »

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arugula

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Re: Timber Retaining wall construction help please!
« Reply #1 on: May 10, 2013, 07:29 »
Perhaps anyone who has read your post didn't feel they could offer sound advice, but perhaps someone who can, still will read it and reply.

Also, it's considered bad form on this forum to bump your post. ;)

Why not go into the Welcome board and introduce yourself. :)

"They say a snow year's a good year" -- Rutherford.

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sunshineband

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Re: Timber Retaining wall construction help please!
« Reply #2 on: May 10, 2013, 07:33 »
I thought your friend's advice was sound and so have none further to give.

As arugula said, please do introduce yourself, and also can you add your locality into your profile as well

Thank you
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snowdrops

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Re: Timber Retaining wall construction help please!
« Reply #3 on: May 12, 2013, 21:52 »
I think you might like to get hold of some books to see if they have pictures to further check that you are on the right lines or google it.
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Trillium

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Re: Timber Retaining wall construction help please!
« Reply #4 on: May 13, 2013, 02:04 »
I'm not qualified to give you expert advice, but regarding Roundup type products, they will work but plants or sod must be left for about 3 weeks for the product to kill the roots. Not sure how much of a hurry you're in, but it appears the sod is gone and it's virtually impossible to spray roots without tops to direct the weed killer to them. If any tops appear you'll have to dig them completely out for best control.

For 'nailing' the sleepers in place, I've done about 6-8" into the soil and found that works provided there is a sleeper step below to brace the weight of all the soil. So, a number of gradual steps can be done.

If possible, get your friend to give you a hand as it's really a 2 person job and between you, you can adapt as needed.

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Stree

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Re: Timber Retaining wall construction help please!
« Reply #5 on: May 14, 2013, 17:00 »
2"X2" posts are way undersized for the potential loading.
Hard to judge scale from the photo, but lets say 1 ton of soil plus a good overnight soaking plus gravity versus 4 posts not much thicker than a piece of kindling made from low grade softwood........
You need minimum 3"x3" preferably 4"x4" of the same number you propose, and if digging out then set the ends in an old bucket full of post mix and backfill the rest with hard tamped rubble. Ideally buttressed as well, but that takes up space. You need a post wrap as well for just above soil level and a foot or so below. This is where even treated posts rot. Post wrap slides on and shrinks to fit with a hot air gun or similar.

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arugula

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Re: Timber Retaining wall construction help please!
« Reply #6 on: May 17, 2013, 15:37 »
We look forward to your progress report(s). :D Glad someone could help. ;)



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