Dissolve yeast and sugar in warm water in a large bowl; let stand 5 minutes. Lightly spoon flours into dry measuring cups; level with a knife. Add 3 1/2 cups bread flour, wheat flour, semolina, and salt to yeast mixture; stir with a whisk until well blended.
Turn the dough out onto a lightly floured surface. Knead until smooth and elastic (about 10 minutes); add enough of remaining bread flour, 1 tablespoon at a time, to prevent dough from sticking to hands (dough will feel tacky).
Place dough in a large bowl coated with cooking spray, turning to coat top. Cover and let rise in a warm place (85°), free from drafts, 45 minutes or until doubled in size. (Gently press two fingers into dough. If indentation remains, the dough has risen enough.) Punch dough down; cover and let rest 5 minutes. Divide into thirds. Working with one portion at a time (cover remaining dough to prevent drying), roll each portion into a 16-inch rope on a floured surface. Place ropes on a large baking sheet sprinkled with cornmeal. Cover and let rise 40 minutes or until ropes are doubled in size. Uncover dough. Cut 3 slits in top of each rope.
Preheat oven to 425°.
Throw water onto floor of oven (avoiding heating element). Place baking sheet in oven. Quickly close oven door. Bake at 425° for 30 minutes or until loaves are golden brown and sound hollow when tapped. Remove from pan, and cool on wire racks. Cut each loaf into 12 slices.