advice requested re the setting up of a raised metal bed

REMF33

OK possible over-thinking alert here but...
I have just constructed a smallish metal raised bed (see below) and the manufactuers advise you to put it on gravel to protect the walls and also to improve drainage. I am a little nervous about putting gravel down. I spent several weeks trying to dig out slate that a previous owner had put down around shrubs, in order to create a new flower bed last spring (elsewhere in the garden). I don't know if they kept applying it but it had worked its way down by about a foot into the ground. It was a sisyphean task. So there is a chance that if I put gravel down, then I will similarly create problems in the future, should I or future owners want to do something else with that bit of ground...? However, the ground is very soggy where the raised bed is to go, at the moment, so drainage would be good and without something solidish, there is a danger that the bed frame, with it's thin, sharp edges will sink into the ground...?
The area where it is to go has some grass on it, but some of it will be bare soil (once I have lifted up the couple of paving stones my husband laid down there last year for some reason not revealed to me...!)
Any advice? I'd like to get going with the bed asap as I have things that need planting out.

I know ground prone to sogginess is not ideal full stop, but I have no choice, previous owner but one did successfully grow in raised beds in this location, acccording to my neighbour and I am willing to take my chances.

This is the frame (not in situ).

Fairygirl

You would use gravel no bigger than pea gravel, which is as the name suggests. It would just work into the soil over time and would never be a problem.  However, on wet ground, gravel of any kind can act like a sump, which isn't helpful. I always prefer to mix gravel into the growing medium if I use it, rather than having a layer of it on the bottom, but it can also depend on the depth of bed. Yours isn't terribly deep, so a mix might be better. 
I can't see that the bed would necessarily sink onto the ground though, unless you were putting pressure on it. Perhaps you could have a layer of brick or similar to sit it on, to mitigate that.  

BobTheGardener

I'd simply place it where you want, put a couple of inches of pea gravel inside, cover than with a layer of permeable membrane (to prevent the soil from the container clogging up the shingle, and to help mitigate tree roots growing upwards), then a mix of topsoil and well-rotted manure to fill it.

REMF33

Ok thanks, both! I probably should have done something with the other (much larger, wooden) beds next to where it will go  when I set them up last year... ah well. The reason I am keen to get this one up and running is that I fear those beds have soaked up the rain. (There is 6 inches in some bits of this part of the garden at the moment ) Should be ok by the time I come to plant them up, but I want to plant out those broad beans I keep going on about asap...
This metal bed kit has been sitting in my shed for two years.


(No, FG it's just over a big cat's height's depth - 40cm )

Fairygirl

Once you have planting in them it also helps with water uptake.
I have lots of raised beds - of varying heights. It's an easier option in my climate, especially on compacted clay. I've always done it, and it means I can grow plants which prefer better drainage, a lot more easily.
I can't change what falls out the sky, but I can mitigate the soil condition a little bit   

REMF33

My new(ish) raised beds were fine last year, but this is their first winter. I think they will be ok. Just not sure about planting in them right now, and since I have this (old) new raised bed, it makes sense to put the beans in that... maybe! 
Will go and stick my hygrometer in the wooden beds this weekend.
The bottom of the garden usually floods in the winter. The raised beds are not located in the worst areas, but it's quite bad at the moment.

floralies

I would also be aware that as it is all metal the soil inside it will warm up quickly. You will need to water it quite a lot in the summer!