I am repainting the cedar siding on my house. Since I have a sprayer, I'm hoping to save time by spraying. The question I have is:

How best to prepare the "channel" component of the siding? The channel is a 1" wide smooth slot, about 1/4" deep, not unlike a dado.The raised surface of the siding is about 4" wide.

I'm not having much in the way of peeling with the existing paint.

My plan at the moment is to scrape the rough portions, power wash, spray paint and then backroll the rough raised sections of the cedar. My theory is that there is not much point to back rolling or brushing the 1" wide channel.

Does that make sense? Am I making a mistake?

  • Hello, and welcome to Home Improvement. A picture of your siding might help; would you edit it into your question? And, you should probably take our tour so you'll know how best to participate here. Aug 21, 2019 at 16:27

2 Answers 2


If the channel of the siding has already been painted, and the paint seems to be adhering well, then you might be able to get away with just spraying over it after a good power wash. It has been my experience that paint in small channels binds better to the bottoms and sides than the surface, compared to a smooth flat surface. However, I'm a big proponent of excessive preparation. If you're going to take the time to paint, the last thing you want is peeling or flaking. It will add some extra work to your project, but I'd take a semi-stiff wirebrush and run through the channels quickly but thoroughly to put some extra teeth into the paint, particularly if the top coat is very smooth. Another option would be to construct a small sanding block, maybe with a 7/8" by 6" face and wrap a 120 grit or similar sized paper around it securing it on the other surfaces with staples. Then you can move the brush or block through the channels quickly scuffing enough to remove any signs of gloss.

Ultimately the decision may be a function of time, whether or not you have assistance, the type of paint on the exterior, the quality of the primer for the undercoat, etc.

  • 1
    A little extra prep is always a good idea.+
    – Ed Beal
    Aug 21, 2019 at 18:41

Do you know what Tannic Acid is in Cedar?

It’s a brownish acid that will bleed through paint and stain if not prepared properly.

Here’s a website that explains it and how to deal with it: https://www.franklinpainting.com/blog/home/tannin-staining-on-cedar-siding/

The stain will affect the groove portion and the face of the siding. Use the proper primer / paint.

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