What determines if you need primer before you paint interior walls of a house?

Primer is for surfaces that have never been painted before. Very few exceptions, you will not run into any when painting drywall, plaster or wood. Never primer over existing paint.





Stain block or stain sealer should be used if there are water or smoke stains that may bleed through a new coat of paint. Stain block may be used to cover deeply contrasting colors, but most of the time two coats of paint will do the trick. With a quality paint applied properly, one coat will cover all but the most extreme contrasts.





Many people will tell you to use primer to block contrasting colors, but this it not technically correct. Primer is designed to seal porous surfaces and depends upon the porous surface to grip. Often times it will work, but it is better to use the proper procedure than take a chance.





People will also tell you to use a stain block product as a primer for bare surfaces. In fact, some stain block products are labeled for this use. While these products will work as a primer for bare surfaces, a good latex wall primer will work a bit better for filling minor imperfections in the wall and does just as well at sealing the surface. As an added bonus, the latex wall primer is less expensive, easier to apply and easier to clean up.





Wall primer for bare walls, stain block for bleeding stains, paint for previously painted surfaces. Always clean well and you will be fine.What determines if you need primer before you paint interior walls of a house?
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What determines if you need primer before you paint interior walls of a house?
I guess if the old color is darker than the new color. Also if the wall has never been painted, or the old paint is peeling, bubbling, or flaking (I would scrape that off though).
If you are changing color, there are patches or you are changing the finish.
If ur using a darker color then ur need to prime ex.cranberry,dark blue,greens. Hope that helps.
i think if a house has raw drywall (new) then primer is recommended. also if you want to repaint a light color over an existing dark color
I would use it regardless. It's a safeguard against so many possible outcomes....bleeding, color stay etc. Take the extra time and prime the walls.
If you have sheetrock or not. or if you go over spackle