My house is 50+ yrs old; through the years various owners have painted over old peeling/cracked paint. It looks horrid. The siding is soft redwood. I have had up to 10 painters/contractors/questioned paint stores about what to do/use to prep/paint–as I am planning to sale in about a year.
Most have said “pressure wash” to remove as much peeling paint as possible. (I’m having GREAT difficulty finding someone just for that), then most said to scrap the remaining peeling paint.
Question: I’ve scraped some of what I can reach.. saying the pressure washing doesn’t remove those edges– do those edges need sanding to make everything smooth? Then, here’s where I get conflicting advise. 1-2 say “use oil based primer, then water based paint”, 1 said “no, use water based primer & paint”, another said “can ONLY stain that soft wood”; then all variations on these advises. I am stumped and afraid to move forward. I hate to sell my home and the owners find it peeling in a couple yrs.
* note* my 88yo neighbors told me 45 years ago those owners “didn’t prime, so it has always peeled within a couple yrs”. I bought it 5 yrs ago. She had had it painted 1 year prior to that. It looked HORRID up close, peeling all over.
Pressure washing is the first step. It might remove some loose paint but don't try to force the removal. Pressure washing can easily damage wood. Scraping is your best bet to remove the loose paint. To make the rough edges smooth after scraping will require sanding. This is especially difficult with redwood.
You could try using a random orbital sander with 60-80 grit discs. Be careful, it will be easy to remove wood and not do much to the rough edges. If this is the case, simply do a good job scraping and leave the rough edges.
O.K., the primer. A stain blocking oil base primer is needed. Redwood has tannins and this will bleed through the acrylic primer, even when they state 'Stain Blocking'. The great thing about primer is you can use any kind of paint over it. For a good result and better experience painting use a good 100% acrylic paint. Using a stain now won't work. You would have to strip the entire house, not economically feasible.
I think that peeling will always be an issue with your house. The lack of primer, when needed, and proper prep has doomed future paint jobs. Do the best you can or hire a good painter to do the work. Not cutting corners now is the only way to get more than a couple years out of the paint job.