How to insulate a metal roof?

Welcome to the Bunnings Workshop community @bowmatty. It's sensational to have you join us, and many thanks for your question about insulating a roof.

That's pretty typical for metal ceilings, and I have a similar issue with mine.

Here are some similar discussions that you might like to check out:

How to insulate Colorbond patio? by @tanmaried

How to stop condensation on a patio roof? by @condruss

How to add insulation to a sunroom with Colorbond roof by @GaryWeiley

How to insulate a patio roof? by @dingo22

The issue is really two-fold and has to do with how cold the roof is getting and the contact with air that's full of moisture. It would be best to insulate the seal and then clad over the insulation. Insulation panels would be easier to install than batts, as you can cut them to size and wedge/sandwich them between timbers. You'll need to install additional purlins that you can screw your roof cladding into before you start with the insulation. There will be different installation techniques involved depending on the type you select. I'd be happy to provide more information once you decide.

By insulating and cladding, you'll stop the underside of the sheets from getting as cold and exclude the moisture-laden air from reaching it. The added bonus of insulating is that it will help reduce radiant heat in summer.

Please let me know if you have any questions.

Mitchell

https://www.workshop.bunnings.com.au/discussion/comment/27966#Comment_27966

Thanks Michell.

Yep I’ve looked at the links you provided and have taken down some ideas.

Option 1: Textured paint the whole underside including the beams. Dont know how affective that will be when finished.

Option 2: Take off the whole roof sheeting and then lay sarking. This is the product im thinking to use- Ametalin 1350mm x 22.25m ThermalBreak Roof and Wall Home Insulation. Once sarking has been covered i will then relay the sheets.

Option 3: Between the underside beams ill measure and cut foil board product ill use- Foilboard 10mm x 2400mm x 1200mm Standard 10 Insulation. Which ill attach the Purlin Brackets for adding the cladding later. I wouldn’t have to take the sheeting off for this right? I have attached a picture of my design thought.

My preferred choice would be option 3 if i don’t have to remove metal sheeting.

Also, i have noticed the condensation only drips from the beams, causing drip lines under the beams onto the floor in the morning. Don’t know if this is just the sheeting trickling down onto beams and then dripping off the beams onto the floor.

please let me know your thoughts on the options?

many thanks

https://www.workshop.bunnings.com.au/discussion/comment/76549#Comment_76549

My preference would also be option three, @bowmatty. You won't need to take the sheeting off for this, but you might need to screw through the sheeting in places to fix the additional purlins/batons in place.

Textured paint might work, as it shouldn't allow the moisture to run and bead into larger droplets before falling off. I was going to mention sarking, but I'm not entirely convinced that it wouldn't also suffer the same effect as the sheeting.

I suspect the water is running down the sheets, hitting the purlins/beams and dripping off them. As it's running down the sheets, it picks up additional water particles on the surface and forms larger droplets. That's why you're getting such distinctive drip lines under the beams. If you get out there early morning with a torch, you'd likely be able to check if there are run lines down the sheets to the beams.

Let me mention a couple of our knowledgeable members, @Dave-1 and @MrSober, to see if they have any thoughts.

Please let me know if you have further questions.

Mitchell

https://www.workshop.bunnings.com.au/discussion/comment/102223#Comment_102223

Thanks Mitchell.

Would this foilboard product be significant enough for my issue? Foilboard 10mm x 2400mm x 1200mm Standard 10 Insulation - Bunnings Australia. Does this product need to have a gap between metal sheeting like sarking?

Thanks again!

https://www.workshop.bunnings.com.au/discussion/comment/118124#Comment_118124

It's certainly going to add a buffer and prevent the moisture-laden air from coming in contact with the cold sheeting @bowmatty. Plaster sheeting over the foil board will add an additional layer of protection. The main issue here is the metal roof sheeting temperature versus the surrounding air. When the air hits the dew point, moisture droplets occur on the surfaces that it comes in contact with. Cold steel sheeting is typically more susceptible to this than other mediums.

Mitchell

https://www.workshop.bunnings.com.au/discussion/comment/127420#Comment_127420

Morning all.

I'm going to go with the Foilboard setup.

My plan is to fit them into the gaps between Purlins (space is 2400mm x 1005mm) and cut them to size.
I will secure them to the purlins with the Flexifast clips.
I will then tape up the exposed edges which should be hidden behind the purlins.
How much space should i leave behind the Foilboard and the metal sheeting?
What shall i do with the exposed roof purlins, as these will still be metal?

Order so far:
24 panels of Foilboard Standard 10mm
Silver tape
Flexifast Clips.
Anything else required?

Many thanks

Dave-1

Morning @bowmatty

Sorry had a flexi yesterday and was stripping old paint off a doorframe. I dont have a lot of ideas about how to fix the condensation but here are a few thoughts.

If there is any air gap between the underside of the sheeting and the tin would condenstaion form?

If you put up insulation and then sheeting to cover it all will the existing trusses you have support it?

Would it be cheaper or possible to install channels on the underside of the trusses/ribs to catch the condensation? As in a small U shapped chanel?

If you take the option 3 with the foilboard foam I hope you post some pics 🙂

Dave

https://www.workshop.bunnings.com.au/discussion/comment/28006#Comment_28006

If there is any air gap between the underside of the sheeting and the tin would condenstaion form? - This is a question i don't know, do i need spacers in-between?

Im happy to just install the insulation at the moment, once satisfied with the condensation issue i will consider cladding over.

Yep, will provide pictures once the job is complete 🙂

https://www.workshop.bunnings.com.au/discussion/comment/76572#Comment_76572

The condensation is formed by moisture-laden air coming in contact with the roof sheeting @bowmatty. If you exclude the air from reaching the sheeting, it can not deposit moisture onto it. By adding the foam board and taping to seal, no air can access the underside of the sheeting. Due to this, I don't believe having a gap between the foam boards and roof sheeting will matter, though the manufacturer encourages you to do so to improve the insulating values of the product. The air gap stops heat/cold from transferring from the sheeting to the foil board and radiating it on the underside.

It appears you've listed everything you need. Perhaps a couple of tubes of polyurethane adhesive would be useful if you need to glue the board to the roof in difficult-to-fix locations.

Mitchell

https://www.workshop.bunnings.com.au/discussion/comment/102233#Comment_102233

Thanks for all your help Mitch! i knew i could count on you guys!

Ill post some pictures with the project to show you always.... 🙂

https://www.workshop.bunnings.com.au/discussion/comment/102233#Comment_102233

I've had a change of plan.

I dont really want to drill into purlins, so ill glue the panels using the Polyurethane Adhesive. DO you think the one you recommended will be enough to hold it permanently in place?

https://www.workshop.bunnings.com.au/discussion/comment/118140#Comment_118140

That's a bit hard to give you an answer on @bowmatty.

According to the manufacturer, they require mechanical fixing. I would presume that if adhesive were enough, they'd have it as a recommended installation method. I am relatively confident that the Sikaflex 11FC would permanently fix them in place, but due to there not being any testing for me to reference, I can't really give you a definitive answer.

Mitchell

https://www.workshop.bunnings.com.au/discussion/comment/127432#Comment_127432

Hello,

I have insulated the underside of my roof with Foilboard 10mm panels.The boards were cut to size and snug fitted. Sikaflex 11FC Has been used to secure in place.

Condensation forms however it evaporates very quick. The dripping as also stopped.

The project was successfully , costing around under $900 for a 60m2 space.

https://www.workshop.bunnings.com.au/discussion/comment/133566#Comment_133566

Winning @bowmatty! What a sensational job you've done there!

That's not a bad cost to solve the dripping problem and add a layer of insulation to the roof that will help prevent heat from radiating down underneath.

Full marks from me as your insulation looks impeccable!

Well done and many thanks for sharing your results.

Mitchell

Dave-1

https://www.workshop.bunnings.com.au/discussion/comment/133566#Comment_133566

@bowmatty

Nice work! That has come up really nice and you have done a professional job on the sheets!

Dave

https://www.workshop.bunnings.com.au/discussion/comment/133566#Comment_133566

Hi there,

I am looking at doing the same. Just want to know how is it working now? Is foilboard still in good condition?

My decking roof is polycarbonate so not sure if can use foilboard.

Cheers,

Handy

https://www.workshop.bunnings.com.au/discussion/comment/137910#Comment_137910

Morning Handy,

Still working and no sign of condensation build up or drips.

I will have to reapply some more adhesive on a couple of the panels as parts have come unstuck (may not have applied much glue in those areas). Other than that, the panels are holding very well.

https://www.workshop.bunnings.com.au/discussion/comment/137910#Comment_137910

Welcome to the Bunnings Workshop community @hank12. It's fantastic to have you join us, and great to see that @bowmatty has answered your question.

Do you have timber rafters to install the boards between? If so, how far apart are they installed. If you don't have rafter spaced conveniently, then the option option might be to adhere the Foilboard to the sheeting. However, Foilboard using gutter silicone for adhesion has only been tested on steel roofing. You might need to do a test to discover whether adhering the boards is a viable solution for polycarbonate.

The other option is to install timber purlins between the rafters, to physically screw the sheets into.

Please let me know if you have any questions.

Mitchell

https://www.workshop.bunnings.com.au/discussion/comment/140309#Comment_140309

Hi bowmatty,

Thanks for letting me know. Good to know it is working fine.

I might use a bracket to keep it in place if I can find something quick and cheap to use.

https://www.workshop.bunnings.com.au/discussion/comment/140310#Comment_140310

Hi Mitch,

I do have rafters, they are 900mm apart. I am for leaning to use a simple plastic bracket that I can nail/screw on so will need 4x per panel.

Is there anything in bunnings that I can use?

https://www.workshop.bunnings.com.au/discussion/comment/142042#Comment_142042

Hi @hank12,

Foilboard Insulation Flexi-fast Fasteners or Foilboard Ultra Insulation Steel Fasteners can be used to fix the boards between your rafters.

Mitchell

https://www.workshop.bunnings.com.au/discussion/comment/143292#Comment_143292

Hi Mitch,

Thanks for letting me know, those items are hard to get in Melbourne apparently. Only few stores have them and they are quite far from me.

https://www.workshop.bunnings.com.au/discussion/comment/144216#Comment_144216

Will you be sheeting the underside of the roof with plasterboard or anything after the Foilboard has been installed, @hank12?

How deep are the rafters?

Mitchell

https://www.workshop.bunnings.com.au/discussion/comment/144898#Comment_144898

I was thinking of adding plasterboard after the foilboard but unsure at this stage. Any moisture damage will cause issue to fix after.

The rafter is 190mm deep.

Cheers,

Handy

jeff-nuancelab

https://www.workshop.bunnings.com.au/discussion/comment/133566#Comment_133566

HI @bowmatty

It is an impressive job on the insulation project! I'm curious about your process. How did you hold and secure the panels in place while waiting for the Sikaflex 11FC adhesive to cure? Did you use any temporary supports or a particular method to ensure everything stayed in place during the curing process?

Thanks for sharing your experience!
Jeff

JacobZ

https://www.workshop.bunnings.com.au/discussion/comment/137919#Comment_137919

Hi @hank12,

The insulation would certainly do a lot to reduce the amount of condensation and potential for water damage, but if you are concerned, I'd advise using Gyprock Aquachek Plasterboard as it is designed to be moisture resistant.

If you didn't want to use plasterboard, the brackets @MitchellMc has mentioned can be ordered very easily through your local store's Special Orders desk. They are a great option that would make installation of the foil board a breeze.

Let me know if you have any further questions.

Jacob

JacobZ

https://www.workshop.bunnings.com.au/discussion/comment/137919#Comment_137919

Hi @jeff-nuancelab,

I just wanted to extend a warm welcome to the Bunnings Workshop community and say how wonderful it is to have you join us.

I am sure @bowmatty will get back to you shortly with an answer to your questions.

Jacob