clear sealant for external shiplap cladding.

[Stringman_uk]

Hi all
we have a summerhouse finished in shiplap cladding, to this we have clad our little shed as an annex butted up to the summerhouse.
As the shed is smaller than the summerhouse the (pent) roof angles up to the summerhouse side wall. It is covered in roofing felt so looks a bit ugly.
So our idea is to cover the roof with tyvek, add some battens and then clad the roof with the same cladding ( it is all pressure treated) obviously the most practical way would to have the cladding running down the slope of the pent, but to fully blend in with the summerhouse we are going to lay it across. I know this means it wont last as long as the other way.
But to give it as much chance as possible I was thinking of treating it with some sort of water repellent/ sealer along the lines of:

No Nonsense Water Repellent Seal Clear 5Ltr - Screwfix

Order online at Screwfix.com. High performance waterproof treatment for exterior porous surfaces. Repels water on wood, brick, concrete, paving, asbestos and cement. FREE next day delivery available, free collection in 1 minute.

www.screwfix.com

does anyone have any thoughts on this,or other products? Ideally want a clear matt finish so its not obvious its been treated.

Many Thanks in advance