What is the easiest and efficent way to smooth a sand textured ceiling? this house is a prebuilt house about 40 yrs old with ceilings 7 1/2' high.
It would depend on how much effort and cost you are willing to invest. Also how large an area is another factor. One way (depending on your DIY skills) is to cover the texture with drywall. Drywall would need to be taped and sanded and primed and painted. I've removed popcorn texture by spraying it with water from a pump sprayer, letting soak-in, and scraping the texture into a plastic bag. I found a scraper made specifically for this work at Lowes. Scraping with water involves plastic drop clothes and afterwards skim coating dents with spackle. I would think both suggestions take about the same time. Drywall might be a bit more costly and labor intensive. Scraping can be accomplished solo with minimum dust produced. But when removing or working with suspicious (or unknown) material that can be inhaled (like 40 year old texture) take precautions by using protective equipment.