# Forum Home Renovation Landscaping, Gardening & Outdoors  Retaining wall built as raised garden bed

## wonderland

Hi everyone, 
I've been looking into landscaping my back yard. I really like the idea of those retaining walls at the back fence to give the garden different height and dimensions. I've read through the retaining wall section of the forum and found out that its not a good idea to build a retaining wall again your fence as the fence isnt strong enough to hold the dirt. Therefore I've decided to build a raised garden bed right next to the fence line so it 'looks' like a retaining wall. Does that sound like a good idea? :Biggrin:  
I want the raised garden bed to be about 0.6m high x 2m wide x 10m long. I am planning on building it out of treated pine, and then putting blueboard on and rendering it. Iwant it to look like something like this: 
I just need to ask a few questions:
1. Do I need to think about drainage for this? I was told by a friend that I dont need  draining as the water will just flow to the earth. But I wanted to make sure.
2. What materials do you suggest I use in terms of what size timber to buy for post and sleeps?
3. Would I need to put any waterproof sheets on the inside of the wall?
4. Would it raised garden bed be strong enough to hold the soil
5. Is there anything else that I should be aware of before I construct it? 
Any help would be greatly appreciated! Thank you thank you!! :2thumbsup:

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## wonderland

Anyone?!
Someone?! 
I really need some advice and guidance.
Thanks

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## Moondog55

Well it depends on how long you want it to last and whether you are going to be eating what you plant. You want to avoid CCA treated pine for edible gardens IMO.
If it is going to be permanent I  would use concrete block, at least 3 course high on all sides.
I have put short walls against fences ( 2 * 200mm redgum ) and filled the gap between the walls with gravel, the post was on the inside, I took the extra weight with star pickets. 
Personally I like the rustic look of weathered redgum, but it has a short life around 20 years. 
I don't think you would need extra drainage if you prepared the base properly by digging down first and maybe adding some coarse bluestone it depends on the soil profile where your raised bed is going to be

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## wonderland

Thanks moondog for your advice. 
I wont be growing any vegetables in the raised garden bed, I will only plant trees and shrubs. I wanted to do the raised garden bed as more of a feature. 
I think 20 years is good enough, but then I would probably want to change the whole design of the backyard again. With regards to drainage, how do I go about preparing the base? What is needed? 
Thanks again, much appreciated.

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## Moondog55

Actually for decoration I would put everything into pots, on a bed of 20mm gravel and fill the space between them with loose and lightweight stuff like broken "Hebel" that way you can re-arrange things quickly and make the best use of suitable screening plants that can take over when planted in the ground, in that case blueboard and render lined with heavy (3mm ) plastic would be what I would do.
Diosma do well in pots and smell beautiful Rosemary/ lemon scented tea-tree/ Lilly-pilly lots of options here

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## Black Cat

Can I also suggest that building it against the base of a timber fence will cause the fence to rot out fairly rapidly due to moisture build-up between the timber and the impervious surface of the raised bed. Better to build it right on the boundary (pending your neighbour's permission) and then install the fence above it, so you don't run into problems down the track when it is less acessible and repairs to the fence will cause damage to your plants ...

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## wonderland

Thanks Moondog. Hrmz not sure about putting them into pots, I would rather prefer to just plant them into the ground. 
Black cat, will the timber fence rot if i build a planter box near the fence? How far do i need to build the raised garden bed without the fence rotting. I've seen alot of display homes where they build these planter boxes right next to the fence, have they done the wrong thing also? Or is there a method to avoid the fence from rotting and still build the planter box right next to the fence line? 
thanks everyone for your advice!

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## Moondog55

That depends on which side the rails and palings are, if the palings are on your side, maybe  just put the blueboard straight up and seal it, that would stop the water from getting through.
Good idea to paint the fence with a preservative beforehand or use H4 palings???

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## wonderland

The pailing is on the other side, not on my side? I thought it was the post which is in the ground that will rot? I dont quite understand. Which part of the fence will rot if i build a raised garden bed near it? I was planing on building the raised garden bed about 150-200mm from the fence. Is that enough distance without causing any structural damage to the fence in the long run

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## Moondog55

My misunderstanding, I thought you wanted to build right up against the fence, if you have clearance then I think you can just go for it and use weed killer to keep things neat behind the garden

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## cherub65

Masonry best option.   

> Hi everyone,
>  I want the raised garden bed to be about 0.6m high x 2m wide x 10m long. I am planning on building it out of treated pine, and then putting blueboard on and rendering it. I want it to look like something like this: 
> I just need to ask a few questions:
> 1. Do I need to think about drainage for this? I was told by a friend that I dont need  draining as the water will just flow to the earth. But I wanted to make sure. Drainage is essential behind any retaining wall
> 2. What materials do you suggest I use in terms of what size timber to buy for post and sleeps? Would build from  masonry not timber as shrinkage will be a major factor.
> 3. Would I need to put any waterproof sheets on the inside of the wall? Water proof masonry wall with min gripset 51
> 4. Would it raised garden bed be strong enough to hold the soil If constructed correctly.
> 5. Is there anything else that I should be aware of before I construct it? You wont get the look your after from doing it the way your considering. Masonry is the the only option. 
> Any help would be greatly appreciated! Thank you thank you!!

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## Black Cat

Mine too Moondog - I also assumed the intention was to build right on the boundary line. If you have a clearance you will be fine. As to your question about what goes on in display homes - well they are there to sell a lifestyle, so yes, things are often not quite what they seem and what looks good with regular maintenance from a garden design firm will not necessarily look that good after 18 months in your own back yard ...

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