If you are NOT going to apply a veneer to your stucco finish - but want to seal the stucco from the elements, you have 2 options.
3 or 4 layers of EXTERIOR LATEX paint (psst - the eggshell finish looks best) is a better sealer than an organic masonry sealer. And every spring, you can scrub the exterior of your oven and apply a fresh coat of paint - it not only makes your oven look spring-fresh clean, but each coat provides an additional layer of protection.
ORGANIC MASONRY SEALER is great for sealing your oven from snow and rain. While the manufacturer recommends a reapplication every 5 years - I would do it every 2.
NEVER USE a sealer that is not ORGANIC as it may contain chemicals that can be toxic when subjected to heat from your oven.
Anyone have thoughts on a product called LastiSeal? It’s an eco friendly sealer with a 15 year life, seems much better than the eco advance siloxane product. The siloxane is organic which seems a step better than just eco friendly, but considering the outside of the oven is so far removed from the food inside, it may be a better and longer lasting choice. It also strengthens the shell not just seals it. Would love a more expert opinion. Hope to spray the entire oven and outer brick hearth and never think about water intrusion again!
Update: spoke to a lastiseal rep and explained the use case. Said it would work perfect. Even around the chimney where it can get hotter on the outside shouldn’t be a problem as the product is rated to 285° and the insulated chimney doesn’t get anywhere near that hot. I sprayed the oven today. Takes 1 coat, absorbs in, and is invisible. Makes the oven waterproof, no water seeping or soaking in through thin parts or mortar or cracks between layers. This stuff turned the oven and outer hearth into kryptonite for water. Water barely even has a chance to bead up before it pops right off the oven. It’s now virtually impossible to get this rig wet. I’m impressed. I also tried eco advance on some other bricks I have and worked really well too. The lesson here was really that stucco is a great finish for the oven and if you use a good sealer, it might as be made out of a wetsuit for all that water’s concerned.