Raised Bed - Treated Sleepers against Concrete Gravel Boards

phillip.austin.26B1YcJxqi

Apologies if this is in the wrong section, I'm a first time poster.

I'm planning on creating a raised bed along a fence using treated sleepers, but am seeking some advice as to whether this is a good idea or not.

The fence in question has concrete posts and gravel boards, with actual wooden fencing panels slotted between the posts and sitting on top of the concrete gravel boards.

The sleepers would therefore use the concrete gravel boards as the back section, and go no higher than the gravel boards (thus not affecting the fence panels).

Is this a good or bad idea?  Will the concrete gravel boards be affected by water retention, weakened for example, over time?

Any advice would be gratefully appreciated, many thanks.

Phil 

Fairygirl

Hi @phillip.austin.26B1YcJxqi - I've never used concrete gravel boards, so I can't vouch for those, but I'd have thought if they were good quality, they'd be ok. 
However, the size of your beds will be a factor - the volume, and therefore the weight, of soil may be a problem, and if you add in the planting [depending on what that is] that could also add to the amount pushing against them. 

Hopefully someone who uses them might be able to advise though. Worst case scenario, you'll need to use more sleepers along the back instead  

phillip.austin.26B1YcJxqi

Fairygirl said:

Hi @phillip.austin.26B1YcJxqi - I've never used concrete gravel boards, so I can't vouch for those, but I'd have thought if they were good quality, they'd be ok. 
However, the size of your beds will be a factor - the volume, and therefore the weight, of soil may be a problem, and if you add in the planting [depending on what that is] that could also add to the amount pushing against them. 

Hopefully someone who uses them might be able to advise though. Worst case scenario, you'll need to use more sleepers along the back instead  

Many thanks :-)

I should've added that detail...  The plan is to use the raised beds for produce; tomatoes, runner beans, mangetout - using supports against the fence.  With additional crop in the ground, such at beetroots, carrots, herbs, parsnips, onions and possibly potatoes.

Rather than one giant raised bed, 2ft wide and 26ft long, I would partition it every 5/6ft.

Fairygirl

I'd say probably ok - but, as I also said, I've never used them  
You wouldn't have as much pressure on them with what you've described. Especially if you're partitioning them. 
You'll have to decide though!

scooty883

The gravel board will have a steel or mesh frame within it.

nick615

If it's any help, these 'boards' have been holding back the contents of this bed (2 High), supported by stout angle iron, for 14 years now without any problem.  I wouldn't think your fence would suffer, but you may consider using suitably faced concrete boards for the whole job?

Fairygirl

scooty883 said:

The gravel board will have a steel or mesh frame within it.

That's what I didn't know. Never used them, so it's good to have that input for @phillip.austin.26B1YcJxqi. Desperately ugly things though. 

Nanny Beach

Hubby says sleepers are a good bet,we have concrete gravel boards on our fence,they are hellishly heavy and expensive. Depends on your budget of course. He says of you go the timber route,make sure the wood is pressure treated,line with damp proof membrane used under house Foundations,don't let any soil touch it. He's also coated every surface with special water repellent seal (Wicks) if you want looking "pretty" you can get stone "fake" sleepers. This isn't our veg plot it's a raised bed for our Ericacious plants. Then you have the cost of soil and compost to fact in. Our veg raised beds are scaffold boards

Loxley

<300mm of soil against the concrete gravel boards would be fine. You might find the fence panels are slightly quicker to rot from the bottom, as they will be much nearer soil level. The biggest risk is wet ground freezing (expanding) and thawing (contracting) in winter. If you're a belt and braces sort of person you could mortar in a row of breeze blocks against the gravel board to give it a bit more mass, and/or provide a gravel strip to help drain water away.