Cement board has been suggested for the above application. I plan to finish with ceramic tile. Since I will be attaching to studs at outermost edges only, due to the necessity of a 1 inch air allowance directly behind above and sides of stove, I've been looking for a full sheet (minimum 48" by 48") or 4' by 8', but can only find Wonder Board in 3' by 5' sheets at local home store. I do not want to seam it or add additional blocking as this defeats the purpose of the air space. Thank you in advance for any ideas.