So we are changing the separate double garage at the end of the garden into workshop/Hobby room/home office. As you can see the majority of the works been done we are currently taking down the false ceiling that's been up donkeys years (we bought the house last summer) as after putting in a suspended floor and lining the walls ( Celotex) is behind both we found a lot of dirt was coming down from above.
After taking down the ceiling and removing the old insulation we have found mice have been living a happy life above the ceiling and coming and going through the gaps at the end of the corrugated roof. Not to mention HUGE spiders 
. I have suggested to my other half that we block these holes up to stop the mice returning. He says no as we need airflow into the space above the new ceiling ( lined with Celotex ) to stop condensation, now I can't find anything online saying Yay or Nay.
Do any of you have a similar roof on outbuildings that are used daily and need to be rodent free.....I do a sewing as a hobby and don't need mice nesting in by fabric stash, let alone eating the tax returns. What have you done to stop this problem or can you suggest where I might be able to find more information?
Thanks