This may have been discussed here before. Is the tape good? What about motor oil or a tar type sealer? To seal top of joists?
Just throwing out ideas. PT wood i know will rot over time no matter what you do.
Im having to replace my entire deck except for foundation posts. Just trying to buy a little more time down the road after I replace it.

Sarge

Sgt.,
I used the butyl tape on the last deck I built (about 3 years ago).....but have no history on protection/durability.

Get the greenish color PT wood for the joists and posts, it won't rot in your lifetime.

My joist have rotted about 2 inches of the top and the deck boards are standard deck boards. Im going to 2x6 decking. Even though it would be time consuming. Im thinking about Thompson waterproofing everything top/ bottom before installing.
I bought several gallons of the stuff off marketplace a year ago at a cheap price. Good way to use it up. Time consuming for sure.
I guess all we can do is the best we can and regular maintenance. But wood is wood. Doesn't last forever.

Sarge

Creosote treated if you can get it in your area for everything except the top boards. The green treated boards are a joke of what they used to be….

Everything is made to be replaced. Nothing lasts. No money in it for the manufacturer.

Sarge

Redwood or cedar

I paint my deck every couple years with REZ.Its15 years old now and I only had to change one deckboard and one railing board so far. They were defective (pitch pocket) when installed.
The rest is still good as new.I also shovel snow off the deck all winter so the surface takes a bit of a beating-why it gets a new coat of REZ every couple years.
I think like everything else,regular mtc goes a long way.
Pressure treated wood is often used where it is not needed.
Pressure treated wood is for wood that comes in contact with the ground.

I bought my current house in 2018. It has a 12 X 16 deck constructed with conventionally treated pine. After the first year I washed it and treated it with Flood CWF (clear wood finish). The second year the same thing. I let it go 2 more years and repeated. I haven't had to retreat for the last 3 years, but will probably do again next year. The Flood leaves the wood with a clear, natural looking appearance. Its usually available at the big box stores.

I first read about it on the Wilderness forum on this site. The guys in Alaska were recommending it. Its probably not as durable as a solid latex stain, but I get to maintain the natural wood appearance vs. a painted appearance with the latex stain. I also used the solid latex stain on a previous house. It's probably more durable than the Flood CWF, but it looks just like paint.

One thing I heard and recommend, don't try to do any finish, regardless of which one you choose, until the pressure treated wood has been in place for one year. That's about how long it takes for the wood to dry from the preservatives in order to get penetration from your finish.

Thompsons Water Sealer is JUNK! It is basically kerosene and will evaporate in one summer. The butyl tape, (it's like rubber and is the same stuff now used to seal windows and doors. It is absolutely waterproof.
Benjamin Moore makes good deck sealers and stains, with Sherwin-Williams running a decent second.

Yup, have to agree with alaska viking, Thompson water sealer is junk.

Flood makes a decent CWF that'll last you two seasons but I find Olympic gives you another year or two on horizontal surfaces.

Solid latex stain looks great and it hides wood that may have deep stains from flower pots and other stuff that a power washer won't remove but unlike your CWFs, it will peel after a couple of years. Then you'll be out there scraping and restaining it every couple of years. With CWF you can pre soak with a pump sprayer filled 1/3 with bleach, 2/3s with water, wait ten minutes, hit it with the power washer and it will look like new again. No scraping or sanding and it costs less than solid latex stain.

Look at the PT retention # on the grade stamp.
Folks think they are saving $ at 30 cents less per.
Or juds keep going to cheapo.