My first post. Forgive if this is answered already. No time to read though all 1'000s of Render subject posts. I'm a total novice but have done some rendering. I wish to make a cement/sand rendered arch (external) on side of garden hut. Roughly about gap would be 8ft high, 3 feet wide. The existing framework is wood on top of blocks (2 high). I was thinking to make plywood 'box' arch, nail chicken wire to it and the wood frame then render over all, say about 1/2 inch, scratch it, then final coat around 1/2 inch again, paint over (masonry paint). I've tried a small area, the render seems to stick ok but don't want to continue with me guesswork though and later it crumbles off. Won't be much traffic. Any advice welcome. Could post pix if required.Ta.