In this paper we report the fabrication of hydrophobic hard coatings using sol-gel processing and cured at room temperature by an ammonia-assisted process. The coating thickness can be tuned from several hundreds of nanometer to several microns. These coatings show both high transparency (better than PMMA or glass substrates) and high hardness (pencil hardness 2H-4H on PMMA). The coatings are very smooth with surface roughness Ra less than 2 nm for coatings with different thicknesses from 200 nm to 2 m. The water contact angle (WCA) of the coating is about 115 to 120o and the sliding angle for a 20 l water drop is less than 10o. The advantage of this process is the ease for larger area application and especially suitable for plastic surface treatment due to the low temperature curing process.