Good evening,
we are currently building and I have a question regarding our garage.
A brief background:
Garage dimensions are 9 x 5 x 3 meters (30 x 16 x 10 feet), attached to the house (fire door), flat roof made of wooden construction (bitumen on OSB board), 180mm (7 inches) rafters spaced about 60cm (24 inches) apart, exterior with 40mm (1.5 inches) plaster base board plus plaster, interior with lime-cement lightweight plaster.
There is a car lift in the garage, and the plan is to heat the garage with an infrared heater for cold temperatures (above the work area).
Does it make sense to insulate the garage ceiling with 180mm (7 inches) insulation, a vapor retarder with taped seams, counter battens, and Fermacell boards?
I have heard mixed opinions so far and would appreciate your feedback. Some say it makes sense because the garage will be heated somewhat, while others warn that the OSB boards might start to rot (although I do not fully understand where moisture would come from; maybe someone can clarify this for me).
My main idea is to simply conceal the beam structure and install spotlights. I want to finish the garage ceiling inside with a nice, preferably sturdy finish. What would you recommend? I’m open to suggestions.
I hope this wasn’t too much text. If needed, I can gladly share some pictures.
Thank you very much for your help.
Best regards,
Kevin Ritter
we are currently building and I have a question regarding our garage.
A brief background:
Garage dimensions are 9 x 5 x 3 meters (30 x 16 x 10 feet), attached to the house (fire door), flat roof made of wooden construction (bitumen on OSB board), 180mm (7 inches) rafters spaced about 60cm (24 inches) apart, exterior with 40mm (1.5 inches) plaster base board plus plaster, interior with lime-cement lightweight plaster.
There is a car lift in the garage, and the plan is to heat the garage with an infrared heater for cold temperatures (above the work area).
Does it make sense to insulate the garage ceiling with 180mm (7 inches) insulation, a vapor retarder with taped seams, counter battens, and Fermacell boards?
I have heard mixed opinions so far and would appreciate your feedback. Some say it makes sense because the garage will be heated somewhat, while others warn that the OSB boards might start to rot (although I do not fully understand where moisture would come from; maybe someone can clarify this for me).
My main idea is to simply conceal the beam structure and install spotlights. I want to finish the garage ceiling inside with a nice, preferably sturdy finish. What would you recommend? I’m open to suggestions.
I hope this wasn’t too much text. If needed, I can gladly share some pictures.
Thank you very much for your help.
Best regards,
Kevin Ritter
It is important to have an air gap with circulation between the roof covering and the insulation; otherwise, the insulation can become wet during the summer. (Outside air warm, garage interior cool → condensation on the vapor barrier on the insulation side)
Additionally, do not use a vapor barrier, but rather a vapor retarder with variable permeability. Simply put, this type of vapor retarder opens its pores on the warm side (roof) during summer and allows moisture to pass through to the cooler side, the garage interior. There are even products specifically approved for flat roofs. Using these should keep you on the safe side.
Additionally, do not use a vapor barrier, but rather a vapor retarder with variable permeability. Simply put, this type of vapor retarder opens its pores on the warm side (roof) during summer and allows moisture to pass through to the cooler side, the garage interior. There are even products specifically approved for flat roofs. Using these should keep you on the safe side.
Hello Evo89
What you can do to be absolutely sure is to hire a professional to give you a quote for the work (you don’t have to accept this offer), then purchase the materials yourself and do it on your own. Be careful: there is no warranty on work done by yourself.
Mold develops when there is a thermal bridge and ventilation is inadequate. That’s why insulation is generally recommended from the outside (for walls). When insulating from the inside, for example the roof, it must be ensured that the interior area is completely separated from the outside—meaning the insulation must isolate the heated area so that moisture does not enter the insulation and cause mold.
Whether it makes sense to insulate there always depends on how often and how long you use that space. If you only use it to park your car, or work there occasionally. If you are not in the space frequently, it is enough to suspend the ceiling and install two ventilation slots (opposite each other to allow cross-ventilation) with manual shutters that you can open and close. If you plan to use the rooms more intensively, for example for gatherings or working on your car, insulation definitely makes sense (provided that walls, windows, and doors are also insulated). For larger events like gatherings, you can also add a portable heater that also warms the pavilion in front of the garage (just to cover every possible aspect).
If you have any further questions, I am happy to assist you.
Kind regards, Ricco Neugebauer
What you can do to be absolutely sure is to hire a professional to give you a quote for the work (you don’t have to accept this offer), then purchase the materials yourself and do it on your own. Be careful: there is no warranty on work done by yourself.
Mold develops when there is a thermal bridge and ventilation is inadequate. That’s why insulation is generally recommended from the outside (for walls). When insulating from the inside, for example the roof, it must be ensured that the interior area is completely separated from the outside—meaning the insulation must isolate the heated area so that moisture does not enter the insulation and cause mold.
Whether it makes sense to insulate there always depends on how often and how long you use that space. If you only use it to park your car, or work there occasionally. If you are not in the space frequently, it is enough to suspend the ceiling and install two ventilation slots (opposite each other to allow cross-ventilation) with manual shutters that you can open and close. If you plan to use the rooms more intensively, for example for gatherings or working on your car, insulation definitely makes sense (provided that walls, windows, and doors are also insulated). For larger events like gatherings, you can also add a portable heater that also warms the pavilion in front of the garage (just to cover every possible aspect).
If you have any further questions, I am happy to assist you.
Kind regards, Ricco Neugebauer
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