Best insulation strategy for a skillion roof?

[DiMcAleer]

Hi I'm getting a bit confused as to what would be the best approach to insulation for a tiny house with a skillion roof. I am in S.E Qld and am very concerned about moisture and mold. I was under the impression that a breathable membrane would be that way to go. But a little unsure of the exact layering strategy. Tin, battens/airgap?, membrane, rafters, rockwool, vapour barrier, fibreboard. Will that work or do I need to add anything else included in this ? Tia

[Jason]

Welcome to the Bunnings Workshop community @DiMcAleer.

One of our resident Bunnings D.I.Y. experts will be happy to assist as soon as possible.

In the meantime, let me tag some other helpful community members who might like to share their opinions: @Nailbag, @TedBear, @JDE.

Jason

[Nailbag]

Sorry @DiMcAleer not may area of expertise. I would probably start getting quotes from professional companies on what they suggest. Then based on their expert recommendations decide whether ist something you want to do yourself.

Nailbag

[EricL]

Hello @DiMcAleer 

You're definitely thinking along the right lines by planning for proper insulation and moisture management. This is especially important for a tiny house with a skillion roof in humid South East Queensland. Here's some general recommendations to help you plan your insulation strategy, with an emphasis on managing condensation and mould risk. Always check with a qualified insulation installer or building professional before you begin, as local codes and conditions may require specific solutions.

You generally start with your metal roof sheeting, then install a breathable membrane directly underneath. This membrane helps moisture escape from the inside while protecting against water from above. Beneath that, roof battens will create an air gap, promoting ventilation and helping to prevent condensation build-up. This gap is especially important in skillion roofs where airflow is limited.

Between the rafters, fit moisture-resistant insulation batts. 

These should sit snugly without gaps or compression. On the inside of the insulation, use a vapour-permeable control layer, never a full plastic vapour barrier in this climate as it lets the structure breathe without trapping moisture. Finally, install your internal cladding like plasterboard or plywood.

Make sure to install all layers in dry conditions and take care to seal around penetrations like lights or wiring. Good airflow through vents or even small fans can help keep the roof space dry. Done right, this setup keeps heat out, moisture moving in the right direction, and your home healthy year-round.

If you need further assistance, please let us know.

Eric