My garage is attached to the side of my house the access is all external and no rooms above it. The eaves of the garage are against the outside wall of the house. Fireproof plasterboard or not for the garage ceiling? I am using the garage as a gym.
Normally two layers of plasterboard with a skim will give the required fire resistance. If you are not involving planning or building control due to a change of use, then it's up to you, any plasterboard is better than no plasterboard and as their is no room above the garage their is no additional fire spread risk.
A garage is required to have 30 minutes separation from the main dwelling. If I understand correctly, you have a masonry wall separating the garage from the main dwelling, this more than achieves this requirement, there is no requirement to protect the roof/ceiling in this instance. Converting to a gym would actually negate the requirement to have a fire resistant wall. For information all plasterboard is fire resistant, however the likes of fireline etc have a higher fire resistance than wallboard etc, however you may require more or thicker layers of "ordinary" plasterboard to achieve a specific fire resistance. There seems to a mistaken belief in this forum that only boards with fire resistant additives are suitable when there is a requirement for fire resistance, Building Regs only states a period of fire resistance.
30 minutes only if required, a single layer of 12.5mm plasterboard with taped joints achieves this in most situations,
Cheers for the replies, I do have a brick and block wall with cavity separating the two. Roof is pitched and tiled. The garage remains a garage on the front with a stud wall halving it. So no change of use its still a garage if you take the wall down. By sounds of it I could use 12.5mm plasterboard for the ceiling or a single sheet of fireboard if I wanted the extra protection. It had 2x 9.5mm boards skimmed on it but they had bowed as fitted poorly so ripped it all out.
In that case there should be fire seperation between the new gym area and garage, this can be done either by extending the wall between the two rooms into the roofspace or by boarding the ceiling to the garage, 30 minutes fire resistance is only required on the garage side so you are only required to board the garage side. This work does not fall within the legal definition of a change of use, contrary to the other poster's advice.