How to replace roof sarking and reduce heat on metal roof?

Sunda

Hi,

The roof sarking of our roof is falling apart.

We are thinking of removing them all, as it is getting very unsightly.

Did some research and apparently to replace them, we have to lift the metal roof to insert new sarking onto it.

Some parts of our roof is quite steep and far from the ground, so we are looking at other safer options that reduce heat of the roof.

The one option we are investigating is to paint the underside of the roof. 

I like to check that it would work?

If it does, what colour is best to reduce heat?

I assume dark colour will not do?

Thank you advance for your advise.

MitchellMc

Hi @Sunda,

You're right that replacing roof sarking involves lifting the metal sheets, which can be costly and difficult—especially on steep or elevated roofs. If the sarking is deteriorating but you're mainly concerned about heat reduction rather than waterproofing or dust control, then there are alternative approaches worth considering.

Painting the underside of the metal roof won’t significantly reduce heat transfer into the area beneath because heat from the sun passes through the metal sheets before reaching the underside. The thermal paint coatings I'm familiar with need to be applied on the top side of the roofing to effectively reflect solar radiation and reduce heat absorption. Instead of painting the underside, focusing on proper insulation installed beneath the roof or using internal ceiling insulation will provide much better results.

Some options include installing foil-backed roof insulation panels or insulation batts beneath the roof. These can help significantly with both radiant and conductive heat. With the insulation batts, you would also then install plasterboard or cement sheeting over the area to neaten the look.

Please let me know if you have any questions.

Mitchell

A note to our New Zealand members: The use of foil-based insulation products is prohibited.