I am after advice on how to fix my rendered fence, over time it has cracked and has lots of marks.
Possibly water damage, i am not sure.
Welcome to the Bunnings Workshop community. It's great to have you join us, and thank you for sharing your question about fixing your cracked rendered fence.
Before you attempt any repairs, I suggest waiting for the render to dry off. If you proceed to repair this now the trapped moisture will push right through the repairs and the cracks will be visible again. When the fence is totally dry, I suggest using Selleys 430g White No More Gaps Exterior Gap Filler in combination with a Monarch 50mm Scraper. The general steps are to cut the tip of the applicator at a 45-degree angle, but only big enough to allow a small stream to come out.
Apply the gap filler directly onto the surface of the crack making sure that the gap filler is forced into the crack itself. The technique to remove the excess filler is to scoop upwards in a pick-up motion. Don't be tempted to spread the gap filler as it will be very noticeable when you repaint the fence. Your objective is to scoop away the excess without spreading the gap filler.
The next step is to find a paint brush with very stiff bristles. Dip the brush in water and whisk away the excess water, brush the surface of the gap filler so that it removes the hard edge and marries into the finish of the render. Once you've covered all the cracks make sure to provide enough time for the gap filler to cure before you repaint the fence.
However, for large, damaged areas it will be necessary to use mortar to fix the damage. I suggest having a look at this discussion if you have bigger cracks to repair - How to fix cracks in render? by @kantoon
Please make sure to wear gloves and safety goggles when reparing your fence.
If you need further assistance, please let us know.