Do I need external rendering to protect my brick wall?
No, brick &amp; its mortar will be fine for 100-years in the weather. You can absolutely Stucco it as well &amp; that will last almost the same amount of time. But, unless the Stucco would be done to match the rest of the exterior, then don't bother. It's just another potential future problem.

However, you can treat the brickwork with a clear Masonry Sealer, only if the brick appears to be wet a day after being rained upon. I say that because the sealer would need to be re-painted every 5-years &amp; you really don't want to add that constant maintenance unless &amp; until you need to.