Raised bed question

[sweet-pea]

Hi all

Has anyone ever used fence posts to construct a raised bed?  I'm talking about fence posts that are around 10-15cm in diameter, and used vertically.  For a design I'm working on I want to continue a theme that is used in an existing bed to create another, but I'm wondering whether fence posts would hold the soil in, what the best way of doing it would be.
The photo below shows the existing raised bed the posts I'm talking about can be seen on the right hand side of the bed.   The new bed will need to be of a similar height as it is for wheelchair users, or possibly a little lower.
Any advice on construction would be gratefully received as I've never constructed a raised bed before.  Also wondering whether using thicker posts would be better, would we need to line them with something, use something like wire to help keep them from splaying out to the sides.  Would it be better to construct the bed using something else and then just fixing half posts around it to achieve the same effect?  What would you use to construct a circular raised bed?

Many thanks

SP x

[sweet-pea]

[Oldmanofthewoods]

4-6" dameter fence posts would be enough to construct a raised bed 3'-3'6" high.  To keep the posts true, fasten pairs of posts together both inside 1+2, 3+4, 5+6 etc, and again outside 2+3, 4+5, 5+6 ad nauseum.

1 2 34 56 78 9
OOOOOOOOO

If the posts don't fit closely, shave a slice off each as you make it.

The bed will have to sit on soil so that the earth doesn't get sour and our friendly wrigglers can get in.

Depending on how wide the bed will be, you might not be able to reach the middle!

(I didn't realise how bad my drawing was!)

Jack

[sweet-pea]

Thanks Jack, how deep would the posts need to be sunk into the ground?

SP

[Oldmanofthewoods]

Conisdering that over time the wood will rot and that if the soil doesn't always drain effectively (like over the last few weeks) making the strain heavy; I would suggest 40% of the post in the soil.  Don't concrete them in though as when the wood rots you'll end up with a glut of concrete in yer nice soil.

Filling it up will take a lot of effort, so complete 75%+ of the circle of posts, then use wheelbarrows to pile up as much soil as you can before driving the last posts in.  After that it would be scaffolding planks to make a ramp or good shovel work!

Don't try on yer own you will definitely bugger yer back.

[sweet-pea]

Thanks again, don't worry, it's a community project so there will be plenty of strong men to help I hope!

[Oldmanofthewoods]

Make sure that us strong men aren't asked to do any thinking!  We find it all too taxing according to my good lady.

[cambourne7]

and you will need a hammer at least 6lb

[Oldmanofthewoods]

No, not a hammer for wood, it will split.  Use a fencing Mell (or Maul if yer from SWest) which has a cast iron head, or a post driver.  A beetle wouldn't do it unless it was half a tree!

[cambourne7]

ah, i just bash them :)

Its great for getting flustrations out just imaging its someones head  and swing!

[Oldmanofthewoods]

Well, I can imagine letting go of one's frustration with a hammer but I would be a tad less than pleased if I wasted anything (as i am a complete tight wad!)

[Eristic]

for long-term stability the posts should be a minimum of 2ft below ground level and the easiest way of installing them is to dig a trench. This allows posts to be maneuvered into precise position with minimum of effort. If creating circular or rounded features, fitting a steel band round the outside will prevent splaying.

Personally, I would use a heavier gauge of timber of the ilk of railway sleepers or telegraph poles but you need to consider the budget, life expectancy and availability of materials.

[cambourne7]

I get my posts from the local wildlife trust for free ( although used ) condition. Usualy they have wire attached which needs to be removed, so try your local trust and see if they have any free posts.

[Oldmanofthewoods]

What an absolutely brilliant idea!  I never thought of asking the local Wildlife peeps.  Thanks for that.  I will tell you how I get on as due to the weather I am thinking of building a dam just over a mile long.

[sweet-pea]

Gosh, I would never have thought of asking the Wildlife Trust, shall get onto it now.

[cambourne7]

I also get the old tree guards off them.

I am currently cable tieing them to the fence around my plot as the weeds are growing though.

Cable ties cost 60pence for 100 from screwfix.

When your on the phone to them re your project you might find that they can also help you with adding bird boxes, a wildlife hotel etc