Flowerbed against house wall

[Fixxxer]

Hi everyone,

I've seen some similar posts, and still thought I'd reach out for some advice. We purchased our house 3 years ago, and the previous owner had literally just finished building a flower bed against the wall. He put all the soil and flowers in a pondlinder, in the flowerbed. The liner is to keep moisture away from the wall, but it is simply retaining all the water and drowning the flowers. The soil is consistently waterlogged.

I want to redo this, and wanted to check the best way to go about it.

The ground underneath the beds/liner is just earth.

I was thinking of taking all the soil and liner out; put a white liquid DPM on the wall of the house, just above where the soil line goes to, and put the soil back in place. The water should soak down into the earth then (theoretically and hopefully ☺).

I had thought about putting a butyl tape on the wall, belts and braces. I didn't want to hang a "loose" membrane, as the rain may get behind it, and not be able to get away. Liquid DPM/tape would be tight to the wall for the water to run down.


Keen to hear any advice, and sorry if these suggestions are just nuts lol.

 

[big-all]

no expert but a fork into the bottom in many places as the idea should be to keep earth and fluids below the damp proof course assuming base well below dpm

 

[Odds]

Take the whole thing out and reline the beds, using a mixture of gravel and vermiculite. Use a light soil and avoid plastic liners so you don't puncture holes in it when turning the soil. Leave a drain hole in each end of the wall to allow excess rain to flow away.

 

[Why Not Indeed]

It seems obvious to me that the liner should only be between the bed and the wall, and not all the way under the bed, otherwise the thing that has already happened would inevitably happen. Your predecessor has basically built a soil-filled pond!
There is probably a better type of membrane to use in this scenario, something that doesn't necessarily need the weight of the soil to hold it in place, eg you can get self-adhesive flashing in 300mm widths ["Flashband"].

Having said all of that...have you considered working with what you have? I.e., planting things in there that like/require a damp environment. I'm sure there are some interesting things you could grow that wouldn't grow elsewhere.

 

[JohnD]

Look at your house and identify where the DPC is. This is very important. It may be easier to see beside or under a doorstep. Once you have found it, it is pretty sure to be at the same height all round the house.

The ground, paving and flowerbeds should be at least six inches below the DPC, usually two or three brick courses, and the house will have been built like that. The DPC must not be bridged by render or plaster or soil or paving.

Unfortunately there are quite a lot of numbskulls who cause damp in houses, usually by laying paving that comes too high, but a flowerbed will also do it.

 

[Odds]

Putting a plastic liner between the wall and soil bed is not a good idea: better off using wood.

 

[Drillbit]

It's better not to have any raised ground against a wall (above dpc); even with a waterproof butyl barrier I would worry about moisture working its way between the wall and the membrane, and just sitting there. If you want to keep a raised bed, I would reconstruct it with a clear air gap between it and the wall. Or have the wall properly tanked. But probably best to avoid altogether.

 

[Fixxxer]

It's better not to have any raised ground against a wall (above dpc); even with a waterproof butyl barrier I would worry about moisture working its way between the wall and the membrane, and just sitting there. If you want to keep a raised bed, I would reconstruct it with a clear air gap between it and the wall. Or have the wall properly tanked. But probably best to avoid altogether.

I had thought about this. How big would the gap have to be? The bed is only about 400mm depth off the wall; 100mm gap would be pretty obvious with only 400mm overall.

 

[Drillbit]

100mm would be too narrow in any case, I think. Stuff would get trapped in there and it would always be a bit damp.

 

[Fixxxer]

100mm would be too narrow in any case, I think. Stuff would get trapped in there and it would always be a bit damp.

So, you think it's doomed? Lol

 

[JohnD]

Dig it out and buy some tubs

 

[scbk]

Get shot of the raised bed against the house, if there's enough dpc clearance you could still have the bed there, just not raised.