The majority of overruns on a maintenance project is usually a result of under estimating the condition of the job site. An example is surface texture. A rough, rocky surface will require more seal coat, slurry seal and crack sealing. Seal coat material, when squeegee applied will require more material to fill in the voids around the surface rocks. The same applies to type II slurry seal. More type II slurry seal is required if a surface is rough or even very rough. If an contractor miss quotes the amount of material required on rough surfaces, a costly overrun can develop. The same goes for crack seal. When the crack is banded during squeeging, the amount of material required to band on a rough surface can lead to high cost overruns on material. Also, should the cracks end up wider after cleaning, more cost overruns can develop. Taking care or doing your due diligence when inspecting the job site to bid, check out the surface texture and where needed, clean a crack with a screw driver to check the width of the larger cracks. If bidding the project right to reduce material overruns will cost you the job, it is better than being upside down at the end of job due to material overruns.
Tom M