Sisalation

[keithvan]

Hello all,

Another newby, first time, boy am I glad I found this site.
I am doing some renovations, and I wonder if any one can tell me, when you put the Sisalation (the shiny paper) on, does it go over the top of or underneath the battens? This is going under Colorbond sheets, and I've got some paperwork that says under, and some that says over.
I'm stumped.
Thanking you in advance,

Keith

[womble]

ours went on top of the battens. I imagine if you put them under there would be greater risk of putting holes in it when you did further work.

[OBBob]

For tiles it goes under the battens. I would have expected the same for tin, because you would come into problems trying to screw into the battens ... the insualtion would want to get caught up on the screw.

Possibly also depends on what sort of roof blanket you are using. Some can be 50mm thick for tin and some are just like silver paper.

Just looked at the pics of my last place and they did go over the battens, however that may just have been becasue the exting battens weren't being replaced.

[DJ’s Timber]

For tiles it goes under and tin it goes over

[silentC]

It can go over or under. Some people prefer it under because the battens hold it in place. However, this can interfere with water (condensation) running down the sisalation. You can also get into arguments about whether it should go shiny side up or down.

One argument for putting it over the battens is that you don't have to roll it all out first, you roll it out as you install the tin. That gives you access to the roof space underneath, which is handy to stand on, pass things up through etc.

I've done three tin roofs now and have always put the wool over the battens, shiny side down.

[keithvan]

Thank you for those replies, it seems to me that as it is to act as a vapour barrier, the water collected has to have somewhere to run to, and as such,it should run towards the gutter, so, Under the battens?
Never to old to learn....

[silentC]

Yes it needs to lap over the gutter, but that doesn't imply that it needs to go under the battens.

I have one builder friend who will not put it under the battens because he believes that any moisture condensing on the paper will run to the nearest batten, then run along the batten to the nearest join in the paper and then into your roof.

[Deanom]

For tiles, yes I do believe you should put the stuff under the battens. The tiles need to be fixed down intermittently with clips nailed to the battens and if the battens are under the foil, this will be more difficult.
For condensation and leakage purposes, if the sisilation is just a foil sheet, putting it under the battens makes further sense on a tiled roof as this should avoid ponding at each batten although this might not ordinarly happen.

I have no idea about steel roofs, but if the sisilation had insulation wool attached, over the battens might be a good idea..

[Deanom]

Another thought on that tile one, if the sisilation is placed over the batten, the tile may not be stable as the lip on the tile needs to get a grip on the edge of the batten. If the sisilation is taught, a firm grip on the batten would be difficult.

[silentC]

I'm pretty sure it's standard practice to put it under the battens on a tiled roof.