HELP! Rendered garden planter walls

[mattypants]

Hi all,

I am extremely worried:

A 'builder' friend of mine has built me 2 walls that join at the ends to use as a planter -rendered with scatch and top coat with a 3-1 mix. The blocks used are 'klinkers' 3 blocks high with no damp course of any type.

I have given this 3 coats of exterior masonry paint which now, after 3 months, has started to bubble vey slightly in very small areas.

The walls are 8" apart on seperate footings and have 12" of dust-free hardcore in the bottom to act as a mini soak away for rainwater. The remaining 20"is partly filled with soil ready to be topped up and planted in the spring.

Will this suffice or should I empty the planter and line the internal sides with say heavy plastic or paintable substance to stop damp coming through the blocks and attacking the exterior render.

They look absolutely superb so I am terrified of them deteriorating over winter to end up having to completey re-render them.

HELP -WHAT SHOULD I DO?

 

[roughcaster]

heavy plastic or paintable substance to stop damp coming through the blocks and attacking the exterior render.

Or the paintable substance, in conjunction with a membrane that can be stuck to the inside of each planter, with a top flap, neatly overlapping onto the top of the blocks, to stop moisture/rain etc getting between the membrane and the blocks.

Roughcaster.

 

[mattypants]

Couldn't overlap at the top as it would be visible and would look awful.

These white, modernist, rendered planter walls can be seen in any upmarket contemporary garden design website . There must be a documented correct way of constructing them........

 

[roughcaster]

Quite right then Matt,,,, you don't want to spoil the overall look. Painting/sealing the insides sounds the best bet.

Roughcaster.

 

[gday2uk]

Did you wait for the render to dry out properly before painting? Sounds like you have sealed some moisture in that has tried to get out after painting hence the small bubbles.

 

[mattypants]

I gave them a week of dry weather.

I have an idea;

Build a marine plywood box that fits snuggly inside the planter walls sat on blocks. The gap can be sealed with exterior silicone to stop water running down the inside of the walls.

I can drill air holes at the base of the walls. This would mean that the inside of the planter would always be surrounded by air and any water draining from the plywood box would drip into the central soak away between the block wall footings.

I have thought of this today. Are there any issues I have overlooked ?