Insulation, Radiant and Vapor Barriers - siding and tyvek

I have to cut a 9 inch thick by 40 foot slot across the back of my house.
The top header is going to fit in to it for an addition.The other side of the house has one and this one is going to be identical.Its basically a shed roof addition about 20 by 40 ft.
I was concerned about cutting through the Tyvek under the siding when I
run the skil saw all the way across the building. About 40 ft.
I dont see how I am going to avoid cutting into the Tyvek.I thought I had heard that you shouldnt cut the wrap or it loses its efficiency.
Any contractors know what the story is here???thanks

If you have to cut the Tyvek, so be it. That's why they make Tyvek tape. You can reconstruct your wrap after your surgery is through by taping additional tyvek into the opening and taping it securely.

I'd be a little more concerned about cutting all the shear walls out, by adding that header! How long is the house? That will be some beam, holding the roof and the addition roof up.
I'm really waiting for the pictures. Be safe, GBAR

Shed roof addition. Unless this is just a porch roof, the picture I have in my head is that all the Tyvek on the walls below this cut will eventually either be interior walls, or walls that will be removed. And your Tyvek will end at the roof line, which will actually be probably 1 1/2" above the cut by the time you put on sheathing and shingles.

So, no, you don't have to worry about cutting the Tyvek. You will obviously have to protect this area from leaks until the work is complete.

yes all below the header will be interior when its done. but not taking anything out.its a cement block wall 7 ft tall with framing above.The header will sit above about 2 ft of the framing.

If I understand correctly, all the interior wall (formerly exterior) will be left intact.

I would frame studs with 2 top plates above the wall to suport the new rafters, spanning both ways. The new addition rafters, and the new over-frame onto your old roof.

You don't need a header (beam to carry loads above with an opening below). Sorry I may have misunderstood. Be safe, GBAR