Outdoor newly rendered wall showing signs rustings on the edges

Question

Hi there

As part of landscaping project, we had new raised plant beds built using grey blocks which were rendered using sand and cement with appropriate additives. We painted it once rendering completed.The edges of these beds where beads were put are now showing sign of rustings that are gradually appearing and growing through the whole length of the beads. The landscaper says it may be paint reacting and we can use stain blocker paint to prevent.

Can you advise probable cause and potential remediations for the same please?

Craig · Accepted Answer

Hi, I think the metal beads they have used maybe damaged or scratched which as a result they have rusted which unfortunately can’t be treated and will continue to rust, I would have personally used pvc beads which are used for most modern rendering and had a silicone render application as you don’t have to paint it

Luke · Answer

Hi I'm sorry to say they have used the wrong beads by the sounds of things they have used galvanised steel beads not stainless steel or plastic so u are always going to have that problem unless you change them cheers lb plastering

Paul · Answer

I would of used plastic external beads for rendering

Kalin · Answer

Only one reason he used galvanised beading used which rust in a matter of months.   As only stainless steel or pvc.   On external.  What some you not trust worthy   Tradesman to put it politely.  Charge for stainless. And use galvanised as they are. Far far cheaper.    You can’t do anything other then remove and replace.     There is a anti rust paint but it’s to late for that sorry to say

Paul · Answer

The plasterer has used internal metal beads which can rust instead of using the proper pvc exterior beads which should be used on any external plastering as they don't rust.

Mark · Answer

It’s the beads that are rusting they are not stainless steel, I would remove beads and fit plastic ones then rerender

Sam · Answer

Hi it sounds to me that they have used galvanised beads which are prone to rust, should have used stainless steel/plastic unfortunately the more rain and wet they get the worse the rust will get☹️

Louis · Answer

Sounds more like he has used the wrong beads. Easy mistake to make but proper external render beads will not rust. I see this all the time. I stick to plastic now to avoid this situation l.

Jason · Answer

Sounds like the beads used are no good. I'm quite confident it won't be painful reacting

Sam · Answer

Should used plastic or stainless steel beads, I think might be best painting them with oil based gloss or something similar

Outdoor newly rendered wall showing signs rustings on the edges

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