Waterproofing a roof from the inside?

I’ve inherited a garage which is great except it’s got a leaky corrugated steel roof

For various reasons I’m not allowed to do any repairs on the roof itself

What would be the best thing for me to put on the inside of the roof to at least stop some of the water getting thru to the floor? I’m thinking some kind of heavy duty plastic sheeting tacked from corner to corner

Are you allowed to stick patches on the underneath? Flashband would work.

You need to stop the water getting inside the garage unless you have some sort of internal drainage system as any repair method that is positioned below the existing structure will just collect water.
Assuming that the corrugated steel roof has holes in it, I would attempt to patch those from the inside with sections of sheet, mastic and maybe fibre glass patches etc.

Yes I can do anything on the inside – needs to be cheap/temporary as the whole set of garages will be re-roofed in 2021

Poke umbrella through hole.

Deploy umbrella.

if its localised and you know where its coming in.

flash band + flashband primer

if its all over and you can leave the garage open to the air for a few days – and its just for storage rather than actually for say turbo training.

Fixrcryl it.

Flexacryl or Acropol will seal 10mm gaps
Good stuff

I used to work at a train depot with a leaky roof above an expensive electrical machine, the repair was clear polythene sheet spread out as an “under roof” with a hose fitting at the low point with a hose going to the drain nearby. It was awful but it worked.

There is a picture on “on the tools” I think

Used some of this recently.
Really good stuff.
https://www.screwfix.com/p/cementone-flexacryl-roof-repair-compound-grey-5kg/46079

Positive pressure. Blow it out…