Spray you fescue grass with herbicide that contains glyphosate sometime between March through September, which is the best time to seed cool season grass, according to Colorado State University Extension. Wait a few days and reapply the herbicide to kill off the remaining fescue grass.
Irrigate the lawn for 10 days to promote growth. Fescue grass that is actively growing will die off better than dried out grass. Spot treat any areas that look green with the herbicide.
Mow the lawn to 1/2 inch in height. Rake up dead fescue grass. Dig up areas where fescue's roots are stubbornly refusing to budge from the soil. Fescue is a shallow rooted grass; therefore, digging up roots may not be difficult.
Till the first 6 inches of topsoil. Apply a starter fertilizer that has an NPK amount of 5-10-5. Broadcast 20 lbs. of fertilizer per 1,000 square feet. Work the fertilizer into the first 4 to 6 inches of topsoil.
Use a rake to grade your soil, so that it slopes slightly away from the house to prevent your new lawn from sitting in standing water. Water the lawn to moisten the soil. Lay down sod from the perimeters or broadcast your new grass seed over the lawn area.