While on the topic of TORCH - ON. AFAIC it's the best way to seal any roof permanently!
Case in point:
A few months ago I redid my front garage roof. This roof was a pain in the butt from day 1 when I bought the house. I have replaced the old rusty IBR sheetings a few times since 1995. the gutter was a balls up, always getting blocked & over flowing inside the garage, since it's on the boundary with neighbour property.
years ago when my neighbour moved in and started extending her kitchen I suggested that while builders are on the property we remove the vibrecrete wall and build a proper brick wall between us, she flatly refused.
Having a proper brick wall would have solved a lot of my roof issues - like my leaking inside gutter, rotten barge board, no proper support for the roof between front & back walls except for 2 old wooden poles and I could remove those god awful glass windows above the vibrecrete wall the previous owner installed.
Fortuitously my GF has a friend that does general metal work and I roped him in to design a metal frame "girder" between the front and back walls with 5 galvanized poles cemented in for support. I had 5 spare poles from my backyard project I also completed in November 2022.
I also wanted 18mm shutter board for the roof with torch on, like my other garage at the back of the house. I'm sick of rusty metal roofs. The back garage roof has been maintenance free / leak free for decades now.
old roof & new metal frame in place on the right - frame will act as a parapet wall later on.
old wooden framed glass panels removed -
new support poles in place with temporary rafter supports till cement is dry
metal work completed - roofing guy onsite removed old roof.
shutter boards in place
new storm gutter leads out to the front garden - the metal girder will also be covered with shutter board
torch on in place

I used nutec boards to fill the gap on my neighbours side. I will also use nutec boards on the inside just to hide the old vibrecrete wall.
all parapet walls & gutter sealed with torch on & painted silver for protection - job done
With all the rain we have had this year so far - I can happily & thankfully say - no leaks!!
So why did I do it this way you may ask?
I do have a signed building plan for a brick wall but If I built a wall I would have had to pay for it myself then I still need pay for the roof. Having a friend - who did some metal work in my backyard last year and knowing his skill set, I trusted him to do the metal work & install it just as I wanted and it didn't cost me much either compared to a brick wall.
The roofing guy - the only one that took the challenge, did a great job. he worked from the Thursday through the weekend till Monday afternoon, he knew the rains were coming.
total time for job - 7 days
total cost for job R65k
Now I don't have to worry about a leaking roof for the next few decades and the roof is strong enough to install solar panels on.
let me know if you want roofing guys details - I'll post it here.