I have a low deck across the front of my house with 2" x 6" x 4' deck boards perpendicular to the house, resting on the 4" edge of 2 redwood beams about 14" high and 22' long. When I removed some of the deck boards, I noticed the lower edge of the siding (texture 1-11) was rotted in a couple of places. What is the best way to repair the rot and protect the wood from further decay? The problem areas don't show when the deck boards are installed, so appearance of the repair isn't a huge issue. The redwood beams restrict access to the damage since the one closest to the house is about 6" from it. Replacing the siding is not an option. Thank you for any suggestions.

Is getting carpenter ants an option? They LOVE rotting wood and WILL find it and set up house... and eat yours. This goes way beyond the visual esthetics.

As difficult as it might be...you really do need to address it.

This particular fir siding, which came in 4' x 8' panels, is no longer made. Among other things, the deck would have to be disassembled to replace any of them. The 2 or 3 rotted areas at the bottom of the siding panels are a few inches wide each and the worst is maybe 2" high, still well below the bottom of the deck boards. I'd appreciate suggestions for treating the damaged wood after removing the rotted areas.

You can actually repair rot once it started. You should scrape and remove as much as you can and then try something like this SYSTEM THREE Wood Restoration EndRot Kit-207166 - The Home Depot

Thank you, ballengerb1, for the suggestion. This is a good possibility. I've used a similar process with Minwax products on window sills, but want to be sure to use the best possible solution because of the access problems (and I'd like the best result, too, of course).

If it is out of sight I would cut off everything out of sight and sister in PT lumber. There is likely no drip edge so water on the deck can sit against the siding. Try to slip some flashing on the siding so it reaches just above the deck

It would be impossible for me to cut off everything out of sight without disassembling the deck since the damaged areas are about 7" below the deck boards behind one of the redwood support beams with a narrow 6" wide "tunnel" to work in. There's no drip edge, but the deck boards aren't in contact with the siding. There's a range of 1/8-1/2" gap from the edges of the boards to the siding above the damaged areas. The siding has vertical grooves in it every 4", maybe making caulking necessary to seal the top of flashing. Sounds ugly. That's why I hoped to repair only the damaged areas. It will still be difficult to reach them in the available space and I'm concerned about the same thing happening again.

You are trying to cut corners and do the job the cheapest way possible, which is not the cheapest way. Smoothy had a good point about the carpenter ants, and I did too have a problem with them. I took down the whole deck and replaced after having someone out to deal with the carpenter ants. More difficult for me surely, as I am a woman and learned the hard way. I spent money to save money !

Fortunately, my house is well maintained and I don't have a problem with carpenter ants. The wood restoration kit suggested by ballengerb1 sounds like the way to go. The rotted areas total less than 12 square inches all together so a more drastic approach is unwarranted. I appreciate getting suggestions from people who are knowledgeable on the subject I needed help with.

Houses that are "in good repair" get carpenter ants and termites all the time. And usually by the time you notice them they have already done a lot of damage. They don't do it where its easily visible. Carpenter ants prefer moist soft wood... Termites prefer dry solid wood.

Without a professionals inspection... its an assumption you don't want to make. It's good policy to have inspections every few years.

Incidentally... there is nothing in or on a house I can not do, HVAC, plumbing, electrical, sheetrock, Masonry, framing, roofing, tile or paint. As can a number of others, some more than others.

An expert already examined the rotted area for invaders and it's fine. I just wanted suggestions on what to use to repair and preserve the wood so it stays that way.

OK... good some people never think about that important thing and end up with tens of thousands of dollars in damage. After all, all we have to go on is a verbal description... sometimes things are worse than they appear on the surface. Hopefully yours IS only superficial because it was caught early.