ICF garage ventilation

[RedRhino]

We are about to sell our ICF house after 7 years, ready to do our next self-build. 

Our buyer's surveyor noted that there was damp in the OSB ceiling (flat roof) of the garage and suggested there was rain water ingress caused by blocked gutters. 

We looked at the gutters and nothing was blocked. We had the roofer back (20 year guarantee) and he was adamant that it wasn't his felt roofing that had failed. Maybe the lead flashing? Maybe the corner where an ICF raised ledge meets the intersection of the garage with the house?
After all the head scratching we realise the damp was caused by a lack of ventilation. The garage door seals shut and is kept shut unless we are outside. The door to the house is a fire door with tight seals. There is no air movement at all and with warm walls any moisture is finding the coldest surface, i.e. the ceiling. 
So that is my lesson for anyone building an ICF garage. You need to consider how the space will be ventilated. 

Edited May 18, 2024 by RedRhino

[JohnMo]

Building regs have specific ventilation requirements for garages - so your first port to take a look into.