Scrape off the old paint I'm pretty sure they had wall painting in mind when they said it. Do you need to scrape off all old paint before painting? The universal answer is No, it's not necessary. You just need to remove all the paint that has failed. Most often, the newly selected problem areas, where the paint has been compromised, must be removed.
Another reason to strip paint is to correct a previous poor paint job. If the paint was applied unevenly, if it faded over time, or if there is a lot of wear and tear, removing the old paint first will make the new coat last much better and will give a more even, polished and finished appearance. If a very thick layer of old paint requires more removal work, less abrasive scraping, than a thin layer of old, peeling paint. Many think that removing paint yourself will save time and money, but this is not always the case.
A new coat of paint from a professional paint contractor gives the property an improved appearance and the walls a new lifespan at an affordable cost. The best way to scrape off old paint on wood siding is to have an organized pattern to check and then remove. It's worth removing layers of old, shiny paint on wooden surfaces, such as railings, windows and doors (especially if another coat of paint means the door doesn't close properly). New paint will generally not adhere better to bare wood than to an old coat of paint.
Some people choose to skip this important step, but are missing out on some of the benefits of pickling. Painting on walls painted many years ago may not seem uniform and pleasant, leading to a waste of time, money, efforts and resources. With either, all cracked, bubbling, blistered, or peeling paint will come off much more easily than old paint that still sticks. Before painting on old paint on wood, all loose, cracked, chipped or peeling paint must be abrasively removed.
I have always been surprised to see workers sanding all the paint on the outside of a house just because some of the paint is peeling off. It is also necessary to remove the old coating if the old paint has cracked, peeled, flaked, chalked, blistered and developed other paint defects, such as pitting, saponification and algae or fungus growth. You should check every area, every sector of the exterior paint to scrape it off, hoping to find it, instead of painting over it. Removing old layers of paint takes years, so a painter may not do that work unless you specify it.