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I'm repainting my house and everything I've read on the subject suggests scraping the old paint before applying new, but it isn't clear if you're only supposed to scrape just the peeling parts or the entire house. My wife thinks I'm crazy for planning to scrape and sand the entire house, and after more than 6 hours of work and probably less than 1/3 of the house scraped and sanded, I'm starting to think she might be right.

On the one hand, there are some areas where the paint looked more or less okay but it's coming off, but on the other hand, not much paint is coming off in most areas. Do I really need to scrape the entire house, or just the areas which are peeling?

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In my experience in painting my own house over 50 years I only sand when necessary, that is when the paint is loose, or, the surface is glossy. I just repainted some trim on my house that has Semi-Gloss paint. And, I sanded it first. I did this to improve the adhesion of the new paint. But, most of my house has flat paint, and I never sand it unless I'm blending an area where I had to remove some loose paint.

Update, 11/14/13: I re-read this today, including all the posts. It's interesting to see the different opinions about this subject. No wonder you had a question after searching the net.

My take on this is that if you are a perfectionist, you'll decide to remove it all. If you're just painting to resell, you'll scrape the loose off and paint. If you're going to keep it and use common sense, you'll scrape, sand where you need to feather edges for aesthetics, and paint. That's assuming its flat paint. For glossy finishes, you really better sand it to ensure the new paint sticks permanently. Incidentally, I always clean before scraping with Tide and bleach solution and brush hooked to expandable pole, and sometimes with a power washer to quickly knock off loose paint. Also, after sanding, I blow off the sanded surfaces with a blower, or brush it with a big paintbrush, or wipe it with rubbing alcohol or water.

Recently I used the tool below to "sand" the loose paint off my deck before repainting and was very impressed with it's efficiency. I like how it gets down into the cracks between the paint and wood and smooths out the ridges, as well as how quickly its use is. You might want to pick one of these up and give it a try.

Finally, one last tip. You can always do a test by painting a small area, waiting several days, then trying to scrape it off. That's how I learned how important sanding is for glossy paint.enter image description here

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I've never heard of scraping paint that is well adhered. Loose and almost-loose paint ought to be removed one way or another down to a layer that is well adhered, or to the substrate. The cause of peeling paint ought to be determined and remedied before repainting.

The remaining good paint ought to be cleaned first, then toothed with either TSP or sand paper or ....

Nowadays, if one of the existing layers of paint contains lead, then special health/environmental safety precautions need to be taken per laws/wisdom.

http://www2.epa.gov/lead

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Thanks for the quick answer. What does it mean to "tooth" the clean paint? Is that just roughing it up? Does it make sense to do the cleaning as the last step so all the sawdust from sanding is gone? –  rob Oct 12 '13 at 1:39
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Yes, toothing is just roughing it up by sanding/TSP/etc... As you say, removing the sanding dust is important. Cleaning as a first step will keep the grim out of the tooth during sanding. Take your time to do a good job. For example, prep all the trim on one side, then paint trim. Prep the siding, then paint it. Rest up for a couple weeks to recover your motivation then do another side. Well, that's my 2-cents fwiw. –  mike Oct 12 '13 at 2:18
    
If you dont scrape off all the paint it will show when you repaint it. Its more for looks than longevity. By your entrances and patio areas take the extra time to sand the paint to bare wood transition. –  Justin K Oct 12 '13 at 4:03
    
requires feathering the transition. –  mike Oct 12 '13 at 4:09
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Just repaint it and any parts that are peeling just scrape those. Paint over the rest.

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You want to remove any paint that is loose. It's not practical to remove all the paint. If you see dirt or wipe your hand across the suface and see /feel dirt or powder, you're best served by washing the house. TSP is the best, but can kill some plants. Liquid dish soap works well, too, just make sure to rinse it well. If you have a pressure washer, a careful pressure washing is usually enough, but there is no substitute for a little elbow grease.

Prime those bare spots with a good primer and paint away! Use quality paint, not the $19.99 per gallon special. If you know a business owner or contractor, you can often buy your paint through their account, paying for it yourself at the paint store. The discounts can be significant.

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