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How to install Foilboard to steel shed tophats at ceiling?

Appreciate any insights on retrofitting

foil board to shed ceiling. There are surprisingly few reputable sources of information on this and the foil board illustrations leave much to be desired.
From the description the https://www.bunnings.com.au/foilboard-flexifast-fasteners-400-pack_p0131086 are what I need for attaching to the top hats - but I just don’t see how this would work, as the top hats have a lip on them for strength, which will make installing these clips a real challenge.

I’m just not seeing how this works without installing some other kind of bracket - but then that presents a challenge in itself, on what is needed there to attach to the top hats.

Any suggestions on what is needed here? Keen for help with steel shed insulation board retrofit instructions, photos or alternatives.
Sincere thanks for the help!

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EricL

Hello @alld01

Thanks for sharing your question about installing Foilboard. If the Foilboard Flexifast Fasteners are not applicable to your situation, I suggest installing light weight pine timber strips on the top hats. I then recommend fixing onto these timber strips using the Foilboard Blank Plates - 250 Pack and your choice of appropriate timber screws.

Here are some of the guides on the Foilboard website:

Here are some discussions about Foilboard installation:

Let me call on our experienced members @Nailbag, @Dave-1 and @AlanM52 for their recommendations.

Just a friendly reminder for our New Zealand members, please note that the use of foil insulation products is prohibited.

If you need further assistance, please let us know.

Eric

alld01

Thanks so much @EricL appreciate the help. With attaching the timber strips, do you mean drilling them onto one of the two thin edges of the top hat?

I suppose too I’m not saying they don’t work just more wondering how those fixings are supposed to work with top hats as the description says they can - I just don’t see how as yet!

EricL

Hello @alld01

I propose drilling them into the side of the top hat not the thin edge. The timber strip must be secure so that they don't move and can hold the Foilboard steady. If the top hat was in reverse with the wide flat end exposed, you could drill into it. If the edge of the top hat was wide enough and strong enough you might be able to screw into it. However, if it is not secure enough it might just split the edge of the top hat edge rendering the fitting useless.

If you can access the top hat or have a sample piece you can look at, you'll be able to tell straight away if the edge can be drilled into and if it will be secure enough.

Eric

Dave-1

Good Afternoon @alld01

I was thinking along the extra timber supports for the foilboard that @EricL has mentioned. Always conscious of the overall weight that is added to a roof structure I would go for a smaller ssized timber and pine at that.

Otherwise the information that @EricL has supplied is what I would be following.

Dave

AlanM52

Hi @alld01,

Like @EricL I also went to the Foilboard website and would simply follow the installation guide.

Screenshot 2025-12-19 232558.jpg

This guide demonstrates how Foilboard panels are installed to the underside of roof purlins or top hats using the appropriate Foilboard fasteners.

https://c33776cf-a0b1-4dec-be28-046a49f15966.usrfiles.com/ugd/c33776_a1fe2d0a4de64f67a876993d3fa9d3a9.pdf

Cheers

alld01

So is the only solution here, to add timber strips to the metal shed? Surprised there isn’t another way to do it - especially as the foil board site and their pretty minimal illustrations don’t help much at all.
But is there nothing else out there, made for retrofitting a metal shed roof (where the wide side of the top hats are used to affix the roof)? Thanks in advance all

JacobZ

Hi @alld01,

Having a look at the Large Shed Structure Installation Guide, as long as your top hat battens are no more than 1200mm apart, then there shouldn't be any need to install anything additional.

You'd just need to use the Foilboard Ultra Steel Fasteners and screw them to the small legs on the underside of the top hat battens. These legs can be a bit difficult to screw to, but I have done plenty of work with steel battens and can tell you that it will work. Once you've installed one or two screws, you'll get the technique.

After screwing them in place, you would use Foilboard 48mm x 50m Silver Tape to tape the seams. The butt joins do not need to happen directly over a batten, which makes things much easier.

This information is all provided in the large, shed installation guide, so you will be fine on Foilboard's end, but you may want to check with the manufacturer of your shed as a precaution. The load applied to the structure would be minimal, but it is always best to be safe and check first.

Let me know if you have any further questions.

Jacob

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