Block work flower bed questions

[Craig24]

Hi all,

I’ve read lots of conflicting information so I’m not sure what to do with my new flower beds.

They’ve been built on my old lawn with a concrete footing and are now in between my new lawn and patio. I will be having them rendered. The lawn at the rear of the flower bed is about 15cm higher than the patio height.

I am unsure as to what I should line them with, if I need drainage holes and do I need to fill them with stone at the bottom?

Any advice much appreciated.

 

[sodthisforfun]

If they're built on the lawn and not a solid concrete base then no, I'd say you don't need drainage because the water should go through your old lawn. If they've a solid base with nowhere for the water to go then yes, you need drainage holes. Stones, that's up to you. Personally I'd not bother unless you are only going to grow seasonal summer flowers with short roots - mainly because you won't need soil that deep for them and good quality soil gets expensive!

 

[Craig24]

Thanks, no not solid base, just a footing.

I think I will be planting some sort of perennials.

Will I need to line it at all? Just worried about the render.

 

[sodthisforfun]

Yeah, I'd line it
Just one thing, is your old lawn good with drainage? If it's heavy clay, then perhaps stones at the bottom would stop your plant roots sitting for months in water. If drains well, then I'd not worry. Was just thinking of my own lawn, it slightly slopes and at the bottom it gets quite bad in the winter for drainage.

 

[Craig24]

Thanks

Would you suggest DPM sheet type stuff or some sort of paint to line it?

Yes in winter it did tend to hold quite a bit of water. I was thinking 150mm of stone or is that over the top?

 

[Craig24]

Something like this

https://www.toolstation.com/bostik-...MIhtqbo9TS6gIVEO3tCh3vMAGSEAQYAiABEgLZCfD_BwE

?

or sheeting I was thinking?

 

[Craig24]

Can anyone advise if BlackJack 901 or 908 would be best?

 

[conny]

908 seems to be the best if you want to avoid poisoning aquatic organisms as it is water based.
901 is solvent based and has a few risks with it including harmful to aquatic organisms and prolonged exposure can be carcinogenic.
Here are the MSDS sheets for each product;

https://www.arconsupplies.co.uk/uploads/pdfs/black-jack-dpm.pdf (908 water based)

https://www.arconsupplies.co.uk/uploads/Blackjack BBP sds.pdf (901 solvent based)

Even though you are not using it to line a pond there is a slight, and I suggest slight, possibility of some leaching into the ground and finding it's way to a nearby water course.
Have a read of both sheets and decide which you prefer to use.