Sisalation paper, also known as roof sarking, should be installed under all metal roofs to prevent damage caused by condensation. It’s a protective barrier that allows moisture to escape while preventing water entering your roof space.
Several of our inspectors have recently observed metal roofs without sarking on quite a few newly constructed properties. This concerns us.
You should know how important roof sarking is so you’re able to make an informed decision when signing the building contract for your new home.
So what causes condensation?
Condensation is moisture that has been depressed from air inside the roof cavity. It typically occurs in the cooler months of the year when warm air inside the roof space comes into contact with the cold metal roof sheeting.
This moisture can either drip directly from the roof sheeting onto the structural timbers, or onto the ceiling below – this usually occurs in flat roofs.
On steeper pitched roofs, moisture will typically run down to the batten, leaching into it (if it is timber); or it drips onto other structural parts and the ceiling.
On very steep roofs, droplets run along the entire length of the sheeting and discharge directly into the gutter; this typically occurs only on roof pitches greater than 25 degrees.
What we recommend:
We strongly advise all our clients to have sarking installed under metal roofs. Excessive moisture is often not identified for long periods of time and can cause costly structural damage to your property.
Sarking also has the added benefit of providing an extra layer of insulation to your home, typically at an R value of .7, which can really aid in the energy efficiency of your property.
Excessive moisture can lead to more than just structural damage. Condensation aids in timber pest activity, this includes fungal decay and termite action as they just love to chew on some damp timber. This is another reason we recommend taking all steps to prevent as much water entry into your building as possible.