Is @pigletjohn or other decking expert around ?

[Tigertigertigertiger]

I've bought a house with a deck.
The wood is dry and mostly sound but with a few bits of rot starting.

It looks completely untreated - almost grey in colour.

Previous owner says it doesn't need treated but I'm not sure if that's correct.

Googling seems to suggest I need preservative and then a top coat but online advice is inconsistent. Can
@pigletjohn or other experts advise please ?

I’m not an expert. Recently had decking fitted and the guys said to Ronseal it once a year. Apparently not necessary but helps.

Main thing is keep it clean and dry, in terms of no leaf build up etc. If there's rot then dig it out and there are loads of decking oils to choose from.
You can find a video on YouTube comparing the different oils but whatever you use you'll have to scrub it and redo it every spring.

If you've got rotting bits, have a look at the sub-frame. We thought we just had a couple of rotting planks and when we looked underneath the frame was really badly rotted. We had to rip the whole lot out (it's a big space) and we patioed it instead.

I thought @pigletjohn was a plumber?

personally I’d always treat decking yearly, give it a good scrub and then wood treatment like a good decking oil. It does rot quickly if not looked after.
I replaced mine with composite. Much easier.

We have wooden decking and use decking stain once every 1-2 years. Its been in about 8 years now and although the decking boards were pressure treated before we bought them, a couple have rotted so I will be replacing them this year. Its also due to be restained this year.

My friend bought pressure treated deck boards and didnt do anything with them. They have lasted ok but look a bit grubby now so he will stain them now as well.

Longevity will depend on if it's hardwood or softwood I think. Composite is easier

Thanks everyone
@ReviewingTheSituation , exactly this is happening re the subframe.

@PocketfulOfMiracles , @pigletjohn is an all round diy expert !