Like walls there is a minimum u value that must be met.
Pitched garage roof insulation.
They are in fact defined as any roof having less than 10 degrees of pitch and need some angle in order to funnel away rain water.
Poor ventilation which can lead to water vapour permeating the internal finishes and insulation is a cause of many garage problems.
If the existing roof of the garage is pitched or if you are intending to build a space above the garage with a pitched roof then we suggest you look at our page on pitched roof insulation which covers this area in a bit more detail.
For pitched roofs i always stick with my old faithful combination of kingsspan kooltherm k107 pitched roof board between the rafters and kooltherm k118 insulated plasterboard for the inside faces.
If the garage is open to the rafters the boards that support the roof use r 38 insulation between the rafters at the roof if they are 10 inches deep.
Before doing anything else take into consideration the type of roof your garage has and plan out your insulation accordingly.
Kingspan with a flat roof this issue does not arise but the u value constraint and the amount of insulation needed is just the same.
Pitched roof insulation between and under rafters arguably the most popular pitched roof solution installing insulation between and under the rafters uses the depth of the structural timbers to best effect.
To get more insulation in the garage install a ceiling and provide access to the space between the ceiling and the roof.
As this requires fitting insulation above the rafters the roof covering will have to be removed in order to fit the insulation.
A full guide on how to do this yourself can be found here.
Before fitting any insulation to the sides of a pitched roof space any repairs to the roof should be completed once the insulation is in place it will be harder to spot any leaks inside the roof and any leaks will soak the insulation itself.
The space created above the garage would also have to be fully insulated in a similar fashion to the garage.
This will allow you to add the needed insulation.
Most garages have flat roofs and despite the name none of them are perfectly flat.
Pitched roofs are fairly simple to insulate and involve the same process as insulating the loft in your main house.
Pitched roofs are a common sight in the uk owing to their versatility and typical low maintenance requirements when compared to other forms of roof construction.
On new build or replacement pitched roofs the ideal build up would be insulation fitted over and then between the rafters giving a big boost for airtightness image credit.
To ensure that i leave sufficient ventilation space i often nail timber stop battens to the side of the rafters.
If it is a pitched roof or if you plan to build a room above the garage with a pitched roof in the future the requirements will be different than if you are dealing with a flat roof with less than 10 degrees of pitch.
