Painting & Wallpapering/Sanding Preparation of Clapboard Siding with Peeling Paint
I am currently preparing the clapboard siding on my garage to repaint with two coats of the same color. This siding faces the South, and the location of the job is New Jersey. Two pictures of the siding are attached.
The last time this siding was painted was ten years ago, and as far as I know, even though the paint was peeling at that time, the surface was barely prepped prior to painting. I would guess that painting job lasted almost five years before the new paint began to peel. As can be seen in the pictures, the paint applied ten years ago was excessively peeling. I was concerned that simply scraping off the peeling paint and painting over the bare wood as seen would cause the new paint to not hold. In fact, at times while using the flat scraper, I noticed that any incidental scratching upon most of this bare weathered-appearing wood caused surface indentations, and the siding itself felt moist.
My question concerns sanding.
I scraped off most of the peeling paint using a flat scraper. Then, using a random-orbit electric sander, I used 80-grit sandpaper to smooth the surface. I was dissatisfied at the results in that only minimal edges of the remaining paint were removed by this process. I really want a good paint job, and I am concerned that painting over splotches of old paint would be sloppy and ultimately unsightly. I then used 60-grit. The results were somewhat better, but again I was left with areas of paint that were resistant and my concerns regarding remaining paint were unabated. I then switched to 150-grit intending to smooth out the surface in preparation for the paint, and hoping that any remaining areas would dislodge. While the surface was indeed smoother, and some small loosened chips dislodged, many of these areas remained intact.
Then I tried 40-grit. This really worked to remove the remaining areas. But during sanding, I noticed that the weathered rough surfaces of the siding seemed to be smoothing out more than I expected. While I am glad that just about all of these stubborn areas of paint have been removed, I am concerned that I may have been too aggressive using the 40-grit, thus damaging and/or weakening some of the rough-side properties of the clapboard.
My ultimate attempt here has been to remove as much of the existing paint as possible so as to have the evenest and flattest surface upon which to apply the new paint. This endeavor has been to achieve the highest quality paint job that will be as durable and long-lasting as possible.
Given the original condition of the siding, as seen in the pictures, should I have sanded as much as I did and used the 40-grit sandpaper even in some areas where the paint was not as badly peeling up near the roofline? And would a final sanding with 150-grit be warranted prior to painting?
I should advise that this is my first attempt at exterior painting. Thank you so much for any guidance you can provide.
Alex, please forgive my delay, but I've been working 90 hrs/wk for the last few months, so everything is at least a few days behind. I read your post three times. Before I get to my answers, let me just say thank you for giving such a clear, concise description of the scope-of-work, your methodology, and the concerns you have.
For this being your first attempt at exterior painting, I'm quite impressed with your level of preparation. You were correct to assume that painting over abrupt edges without sanding would have resulted in yet another premature failure. Sometimes it's a learning process on each home as to which abrasive will be most successful. There was nothing wrong about using 40-grit, but it should be followed by using either 80-grit or 100-grit to help smooth out any waves or grooves caused by the 40-grit, and then finished with 150-grit or 220-grit.
As far as whether or not you needed to be as thorough on the areas near the roof-line where it wasn't peeling as badly, I can only guess, since I don't know what those areas looked like before. I WILL say that it is wise to err on the safe side and remove any questionable areas, since even the areas left in-tact would have likely begun to fail soon, so your decision was correct to remove as much as you did.
If you use a high-build primer, it will help to smooth out some of the imperfections left behind from scraping or sanding. I'd advise using an oil-based primer. You'll need the tannin-blocking powers that only an oil can provide, (the brown oil-stains which seep through latex primers are the tannin).
If you still have quite a bit more paint removal to do on other sides of the home, you might want to consider investing in a PaintShaver Pro. They aren't cheap, but they make very quick work of stripping clapboards. Here's a link:
Also, if your home was built before 1978, there's a good chance you're dealing with lead paint. If that's the case, I hope you're being responsible with all of paint chips and debris, since it's highly toxic. Even the sanding dust on your clothes is enough to cause serious harm to you, your animals, and especially children. If you can afford to purchase a sander/vac combo from Festool, you won't be disappointed. The dust collection systems on them are the best in the world. If you DO consider getting anything from them, please contact me and I'll give you my insights on which sanders are best for the money. Here's a link to their site:
Please keep me posted regarding the process and let me know if you have any further questions/comments. The work you're doing on this home is exactly what I do for a living, so I'm sure I can provide assistance if more is needed. Good luck and keep in touch.