Waterproofing a rendered block planter Brickwork, drystone walling, render are a few subjects covered here. Click here to post questions and get answers

[renfrew999]

Hi. I'm building a large rendered planter from concrete blocks and I've read that its advisable to paint the interior with tanking paint. My question is, as the soil will not be to the brim I will need to render the top 10cm or of of the interior. If I paint that section with the waterproof paint will the render adhere to the blockers or should I leave that section free of paint? Thanks in advance

[stoneyboy]

Hi renfrew999
Concrete blocks are porous, if the inside is going to be painted it is impossible to fill all the fissures and stop damp from the soil entering the blocks. With the outside rendered some areas of the rendering will eventually blow by frost action. It will therefore make little difference if you paint to the top but probably better to leave the top few cm unpainted.
Regards S

[renfrew999]

Thanks for the reply. Having read up I think its tanking slurry that'll be using the paint the inside of the planter

[stoneyboy]

Hi renfrew999
If you haven't started building the walls yet it would be wise to consider using 3+ rows of engineering bricks at the base to form a DPC but leave the lowest ones un-rendered.
Regards S

[renfrew999]

Nearly finished it but thanks for the advice! It may help someone in the future.

[renfrew999]

Would it make more sense to line the planter with dpm as opposed to painting it with tanking slurry?

[stoneyboy]

Hi renfrew999
My preference would be to form a mini soakaway in the bottom and use a pond liner but pierce holes in the bottom.
Regards S

[stoneyboy]

Hi renfrew999
My preference would be to form a mini soakaway in the bottom and use a pond liner but pierce holes in the bottom for drainage.
Regards S