Do you waterproof a brick garden bed?

[Samc1234]

I have built a brick garden bed. I will render the outside, however, do I need to do anything to the inside. I will render the inside only about 5-10cm down due to aesthetics. Do I need to waterproof or prime the inside?

Thanks

[MitchellMc]

Hi @Samc1234,

Yes, it’s a good idea to waterproof the inside of your garden bed with something like Crommelin 4L Blackseal Heavy Duty Bitumen Waterproofing Membrane, as long as you have drainage at the bottom to let water escape. The reason is that soil holds moisture, and this moisture will seep into the back of the brick wall. If the inside isn’t waterproofed, water can travel through the wall and show up on the render, which can discolour it, especially if you’re using a lighter colour.

Additionally, if you plan to paint the wall later, moisture from the soil can push through and cause your paint to peel, flake, or bubble. Waterproofing the rear side of the wall when you have the chance helps prevent these issues.

Just make sure that if you waterproof the inside, you have drainage points at the base of the wall. Without them, water cannot escape, and you will end up with a pond instead of a garden bed. 

If you're going to be planting food crops in the garden bed, we might need to look for a different waterproofing product as bitumen wouldn't be the best.

Please let me know if you have any questions.

Mitchell