Garden wall rendering

[NotYourFather]

Hi all - I think I'm a fairly competent DIYer, but find that there is no substitute for advice provided from experts and those that have tackled the same jobs before me!

I'm just building a seating area in my garden and then laying slabs inside the area once complete. The seating area is about 3/4 foot higher than another area I plan to slab meaning that one of the walls is slightly retaining.

I plan on laying concrete foundations and building the wall with concrete blocks. My initial plan is to lay a single course of blocks and then paint a bitchumen paint of some sort to prevent the water raising from the ground (which is incidentally clay). Then complete the wall in blocks and render the whole lot. Finally finishing everything off with a decent breathable paint. I'm also planning on capping the tops with some hardwood that should help with any water running directly down the walls

Given that both new patio areas will be sloped slightly so that water should run away from the walls and given I've reduced the amount of water that should seep from ground level, would a decent waterproof render mix be suitable for the render in order to avoid frost damage and water damage? I don't really want to install a bellcast or anything that would remove the clean lines I'm after?


All advice much appreciated

 

[tony1851]

Rendering garden walls is not usually a good idea, particularly if they are retaining walls.

 

[NotYourFather]

That's what I read - but I've also read that it's ok if done properly. The retaining aspect is less than a foot and as I'm laying slabs on boths sides, I'm planning on dropping 80mm of hardcore below the bedding mortar which will almost entirely remove any water from actually sitting directly on the wall.

That was my reasoning for the bitchumen. The actually ground water (in my opinion) shouldn't be too much of a problem. The only real water ingress I feel is that which will travel up the render from the slabs (and only in rain and settled water on the slabs). With a decent render, shouldn't I be able to prevent this as well?

 

[r896neo]

I have learnt my lesson regarding garden rendered walls retaining or not. Use a dpc at ground level then paint synthapruf on to the wall for a foot above that. Then dont render down into the ground and butt your paving against it but instead put a stop bead about 25mm above your paved surface. This will stop water tracking up through the render which has happened to me on a free standing wall on free draining ground!!

 

[NotYourFather]

So basically just a stop bead just above the paving just to prevent water ingress from contact? Would you run your paving under the stop bead or shingle under the bead and run the paving against the point that the render would have ended?

 

[r896neo]

Run the paving under the stop bead. Its just to create a break so your render cant transfer water up the wall. You either need to be super accurate with your positioning of the bead or render after the paving is done

 

[NotYourFather]

Really appreciate the advice - I'll post the results in a few weeks so others can see an example of what you've suggested