Where do you live? 20 gals of 12.5 and 40 gal of water will give you a nice low 3% mix which is what most asphalt shingles will need. Add about $8 of snotmenade, how do you figure your costs at $260. I figure my mix runs just under $1 per gallon ready to go. Snotmenade is .15/gal of mix, so even if you were paying $5/gal for SH you’d still be under $2/gal for your mix.
So even at my price for 1 story roofs of $.20/ft - each gal of mix should cover 50 sq ft, maybe more if shallow pitch, which we rarely have,- you do the math.
