How to repair render on garden wall?

[DIYKeith]

Hi all, looking to refresh my worn down rendered garden wall without having to re-render the whole thing (total wall is approx 12 metres). Some sections just need a new coat of paint, whereas others (image attached) need some larger patching due to the paint easily pealing off. If I had loads of money, I’d of course get the whole thing re rendered however looking to save some money and learn, so I’ve done some research and am looking to use Exterior Masonry Poly Filla for the patches and then 1-2 coats of Dulux Weathershield Render Refresh Crack Bridging Paint Low Sheen. My question is: will this suffice? Do I need to apply a render compound as well and or/ should I apply any water proofing membrane first? It’s an old wall and some moisture has come through causing some calcium buildup up and the paint to peel over 20-30 years. (Not sure if it was ever internally waterproofed, unlikely!) Hoping my plan above will work to make it look “refreshed” but welcome any tips if I’m dreaming or if there is anything else I should be aware of or consider. Thanks in advance! Pic attached. 

[MitchellMc]

Welcome to the Bunnings Workshop community @DIYKeith. It's wonderful to have you join us, and many thanks for your question about repainting an external wall.

From this image, your render doesn't look bad; it's the paint peeling off. I can't see any reason why you'd need to re-render this wall.

If you have a high-pressure sprayer, it would be a good idea to run it over the wall to see if you can blow any more loose paint off it. It's best to get it off now before you re-coat the wall. After you've done that, take a scraper and chase the loose paint back to see if you can reach an area where it is still bonded well to the underlying layer.

What you've suggested sounds quite reasonable. You'd only need to use a rendering compound if sections of the wall need to be resurfaced or chunks of cement were falling off. If you are patching with the Masonry Poly Filla, there is no real need for render. However, before applying your top coat, I recommend using Dulux 1step Prep over the paint and your patch work. Also, make sure to clean the existing paint down thoroughly with Sugar Soap.

If the wall has lasted 20-30 years, I'd be inclined to just paint it and hope for another couple of decades. You could dig out behind the wall and add a waterproofing layer there, but it needs to be on the backside of the wall to stop water from entering it. It looks like accessing that area will be quite difficult.

Please let me know if you have any questions.

Mitchell
 

[DIYKeith]

Hi, @MitchellMc, legend, thanks for the quick reply! All that sounds good and yes, will get the pressure sprayer on it. Any recommendations on how long I should wait after spraying for the wall to be dry enough?  Does it need to be 100% dry? I’ve found that after already stripping some of the paint the wall can still be “moist” in some sections (no thanks to Sydney rain and shade) as well.  I’m sure completely dry is ideal but with moisture behind, not sure if that will ever be perfect, should I just make sure to apply the Polly filla to any stubborn moist areas before Dulux 1step prep. Thanks again, Happy Easter! 

[MitchellMc]

Happy Easter to you, too, @DIYKeith. Ideally, it would be best to work with a completely dry wall. I'm in Sydney as well, and everything is wet.

Given the 1-step and topcoat are water-based, I would believe you'd be fine applying it to a slightly damp wall. It's obviously going to take longer to dry, though. You can only really just give it a go and hope for the best. Without waterproofing the back of the wall, it's always going to be slightly damp. If you pressure spray and clean the wall down now, I'd wait until tomorrow to paint. If there is full sun on the wall today, you might be right by this afternoon.

Poly filler isn't going to do anything for the moist areas. In fact, I'd recommend using it sparingly on those areas to fill any damage and go straight on with the primer.

Mitchell

[DIYKeith]

Thanks again @MitchellMc