Another raised bed question

[werth]

Hi!

I'm planning to build a raised bed for some shrubs in this area using 200 x 100 mm treated softwood sleepers.
It will be roughly 3.5 by 0.5 metres and two courses high.

Would it be ok to build the bed against the brick wall, or would it be better to leave a gap and build all four sides out of sleepers?
If I build it against the wall, what is the best way to damp-proof the wall?
Would this be suitable: https://www.screwfix.com/p/thompsons-water-seal-clear-5ltr/52043?

For the foundation, I was planning to dig a small trench, fill it with gravel and then place the sleepers on top.
I'm not sure if cement is needed at all.

Also, based on the approximate plan I've got, there's a buried power cable that should just barely miss the bed.
For this reason, I was going to leave that corner alone, but use a few sleeper spikes everywhere else to secure it.

Am I missing anything? It's my first time doing this, so any advice would be much appreciated!

 

[StephenStephen]

It's worth bearing in mind that the sleepers won't last a very long time, but you'll get a few years out of them, especially if you line the inside with old compost sacks or other plastic.

Is that the wall of a building or a garden wall? (Makes a difference to whether or not you need to keep it dry).

Out of curiosity as much as anything - why not plant the shrubs in the ground? They'll struggle not to dry out in a raised bed.

You don't need a foundation for a wooden raised bed - they're often just fixed together and sat on the ground. Gravel could add to the problem of the shrubs drying out.

 

[werth]

Is that the wall of a building or a garden wall? (Makes a difference to whether or not you need to keep it dry).

A garden wall

Out of curiosity as much as anything - why not plant the shrubs in the ground? They'll struggle not to dry out in a raised bed.

Oh I didn't think of that, plants drying out.
My thinking for using raised bed was that the soil is very bad with lots of stones, pieces of bricks and rubbish, so I was going to fill the bed with topsoil/compost.

 

[werth]

Also, I'm wary of digging on the right-hand side of the photo because of the power line I mentioned.

 

[elisa123]

I agree with #2. You will also need an awful lot of topsoil/compost to fill the bed.