How to stop condensation on patio roof?

Welcome to the Bunnings Workshop community Shane (@condruss). It's sensational that you've joined us, and many thanks for the question about enclosing your patio.

It sounds like the temperature and humidity conditions are reaching dew point as moisture will then condense on the underside of the metal roofing. When warm air comes in contact with the cooled sheeting, the drips form. Do you experience this issue mainly in the mornings?

To stop these drips from falling within the newly enclosed area, you can install a vapour barrier under the sheeting to prevent contact between moist air and the sheets. Any drips that do still form will be directed down the sarking and out of the area. This type of installation would be most effective if you removed the sheeting before installing the sarking. Insulation batts can be used between the rafters and then cladded over with HardieFlex sheeting to complement the sarkings installation.

If you post some images of the area, it will give our helpful members an idea of what you're working with, and they might have some other solutions for you.

Please let me know if you have any questions.

Mitchell

https://www.workshop.bunnings.com.au/discussion/comment/15077#Comment_15077

Hi Mitchell,

Thanks for the response. The problem occurs mainly in the mornings. I’m not sure how to go about installing any product as it is a single sheet. I’ve included some photos. Your advice and help is appreciated

https://www.workshop.bunnings.com.au/discussion/comment/70101#Comment_70101

Thanks for the images, @condruss.

OK, that's a bit different. I presumed there would be some structural elements (rafters) supporting a roof over that distance. Since this isn't sheeting on rafters, it negates my previous suggestion.

If it is a single sheet, it limits your ability to fix anything to it as well. You couldn't really baton out the roof and install sarking or fibre cement sheeting, as the screws would penetrate the roofing sheets, leading to all sorts of headaches.

Let me mention @TedBear, @Brad and @tom_builds to see if they have any thoughts. My colleague @EricL might also like to join the conversation.

Mitchell

TedBear

https://www.workshop.bunnings.com.au/discussion/comment/98124#Comment_98124

That's a tricky one @condruss. You are fighting the forces of nature outside, where nature usually wins.

Options will depend on how far you are going with your alterations.

I'd suggest that you either try to insulate the bottom of the metal somehow, such as stick on rubber strip https://www.bunnings.com.au/moroday-750-x-10mm-x-1-8m-adhesive-foam-roll_p4000005, or

prevent the condensation from forming into drops by applying a textured paint. It needs to be rollered on, or dabbed. You could even try gluing on rubber backed tiles.

If you are enclosing a section, could you design that section to have its own ceiling? Then you could put insulation in that area at least.

https://www.workshop.bunnings.com.au/discussion/comment/115766#Comment_115766

Thanks for your comments. All great ideas. We are thinking about turning a section into a room that would have insulation and a false ceiling but would like to treat whole area first. I’m curious about the textured paint. How would this work? Does it have sand or grit in it? What qty would I need for a 10x3.5 area? How many coats? What would I clean and prep roof with? Here is another picture from this morning. Although not beads you can see moisture. Thanks Shane

TedBear

https://www.workshop.bunnings.com.au/discussion/comment/125816#Comment_125816

Hi @condruss , Yes, textured paint has grit in it. It should give some insulation from the cold metal and also the rough surface will make it harder for any moisture to form into drops, so it can then just evaporate away with air flow.

Another option would be to mount some fans on the wall and have them blow air across the ceiling, but the passive ideas don't require any management by you, once installed. You could just use the fans before you intend using the outside space.

Quantities and prep for your situation would be best discussed with the paint department, but it tends to be sold in large tins and is reasonably priced. I used some on a sunroom wall to hide the many patches from alterations and applied with a fluffy roller. Maybe @EricL can also add something there, he seems pretty good on products.

https://www.workshop.bunnings.com.au/discussion/comment/132552#Comment_132552

That’s great news for the textured paint. Can I get this to match the colour of the patio roof? What quantity will I require for a 10x3.5 area, what equipment and materials and what to use to clean and prep the area? Roll on sounds best application. I’ll have to order online and arrange pickup. Thank you all

https://www.workshop.bunnings.com.au/discussion/comment/136668#Comment_136668

@condruss,

@EricL will be back on the site after the weekend and will share his expertise with us. However, you'll find that most commonly available textured paints are compatible with brick, cement render, fibre cement, and masonry surfaces. I haven't personally heard of any that will adhere to a powder-coated surface. We might need to investigate with our suppliers to see if there is a primer that you could use that would allow the paint to adhere in this particular application.

Mitchell

https://www.workshop.bunnings.com.au/discussion/comment/139502#Comment_139502

Thanks Mitchell. I hope the paint will adhere. I’ll wait a response. Ta

https://www.workshop.bunnings.com.au/discussion/comment/141418#Comment_141418

Hello @condruss

It's great that you've received excellent suggestions from @TedBear and @MitchellMc. If you are going to paint your powder-coated ceiling, I suggest using the Dulux 4L PRECISION Maximum Strength Adhesion Primer White. This would be the ideal primer to use as it is formulated to work on difficult surfaces to paint. However, I suggest speaking to your local store's paint specialist about the textured paint and see which one will be ideal for your situation.

I recommend using the Dulux 4L Medium Texture Exterior Paint. Your goal is to create a surface with the maximum amount of hills and valleys in your texture. This will prevent the moisture from joining together to form condensation. Please keep us updated, we look forward to seeing your ceiling textured and moisture-free.

If you need further assistance, please let us know.

Eric

https://www.workshop.bunnings.com.au/discussion/comment/142859#Comment_142859

Thanks Eric. I’ll try and chat to my local paint specialist though a little hard with lockdown. Can you advise best materials to clean roof with to make sure paint adheres well? Thanks

https://www.workshop.bunnings.com.au/discussion/comment/143870#Comment_143870

Hi @condruss,

A scrub down with a broom and SugarSoap would be sufficient to clean the area prior to priming. Make sure you rinse the SugarSoap off with fresh water. You might also like to use a pressure washer to speed the process along or if there is a heavy buildup of grime.

I'm sure @EricL will get back to us if there is anything else to add.

Feel free to call your local store, I'm sure their Paint Specialist would be more than happy to discuss this over the phone. Dulux also has an amazing Live Chat on their website for technical assistance. I often find myself taking advantage of it.

Mitchell

shawmat

https://www.workshop.bunnings.com.au/discussion/comment/15077#Comment_15077

Hi @MitchellMc

Could you please elaborate on this more?

I have a truss like patio setup which has condensation and what appears to be white salt buildup all along the beams. I have been told I can just clean this although Id prefer to head down a less maintenance heavy setup if possible.

Thanks in advance

Matt

https://www.workshop.bunnings.com.au/discussion/comment/71128#Comment_71128

Welcome to the Bunnings Workshop community, Matt @shawmat. It's fantastic to have you join us, and many thanks for jumping into the conversation.

I'm happy to elaborate. What did you require more information about? The process I explained above involves having insulation placed against the underside of the sheets and enclosing the roof structure. This reduces the extreme temperature difference the sheet experience going from frigid nights to sun-warmed mornings. The setup is more similar to what you'd see inside a house's roof instead of a patio.

I'm keen to hear more about this white salt-like buildup and see some images of what you're working with.

Mitchell

shawmat

https://www.workshop.bunnings.com.au/discussion/comment/98784#Comment_98784

Hi Mitchell

Have attached photos above of existing setup. Hope this helps to portray issue a bit better.

Cheers

Matt

https://www.workshop.bunnings.com.au/discussion/comment/116164#Comment_116164

Hello @shawmat

Thank you for posting the photos of your patio. I suspect that these are mineral deposits left by the water condensation on your patio frame. Have you tried to brush them off or are they difficult to remove? If enough minerals are deposited, they will become very difficult to remove as they will start to attach themselves more permanently to the frame.

Earlier in the discussion, we were exploring possible methods of preventing condensation from forming on the underside of the patio roof. Some of the suggestions offered are below.

Install sarking or Insulation batts to be cladded over with HardieFlex.
Use Moroday 750 x 10mm x 1.8m Adhesive Foam Roll.
Apply Textured Paint to prevent the condensation from joining together, creating water droplets.
Build a proper ceiling enclosure.
Use Bristol 750mm Wall Industrial Wall Fan to increase wind flow, and dry off the condensation before it forms.

If you have any other questions, please don't hesitate to post them. Our members will be more than happy to provide advice and information.

If you need further assistance, please let us know.

Eric

shawmat

https://www.workshop.bunnings.com.au/discussion/comment/126094#Comment_126094

Thanks for this information Eric.

It is quite a large area so definitely wanted to do something more permanent rather than having to wash it off yearly.

In terms if the options ..

1. Would the structure generally be designed to handle additional weight of hardieflex

2. Adhesive foam roll - would this be purely just applied around the beams?

3. Textured paint - is this quite successful

4. What does a ceiling enclosure build entail? Excuse my ignorance.

5. Area bit too large to be covered by the fan

Thanks in advance

Matt

https://www.workshop.bunnings.com.au/discussion/comment/17085#Comment_17085

Hi @shawmat

You'll have to speak to your local builder to know if any extra support framing needs to be built to hold the HardieFlex weight. The Adhesive foam roll can be applied to the beams, but if your getting condensation on the ceiling panels You'll probably have to put some of the rubber there as well.

Let me tag @condruss to see if they went ahead with the textured paint. A Gazebo ceiling enclosure is similar to your house's. enclosure. A timber frame is made, insulation is placed, and viola! Your patio now has a proper ceiling. This structure will now protect the area from getting too much condensation.

If you need further assistance, please us know.

Eric

Rohan123

Hi Eric, What type of brush and technique to apply the Dulux 4L Medium Texture Exterior Paint.

It is being applied to corrugated colorbond in a patio with the objective of reducing or eliminating condensation.

As you have siad , the goal is to create a surface with the maximum amount of hills and valleys in your texture.

Thanks

https://www.workshop.bunnings.com.au/discussion/comment/76800#Comment_76800

Hi @Rohan123

Welcome to the Bunnings Workshop community. It's wonderful to have you join us, and thank you for sharing your question about what brush to use for Dulux Textured Paint.

The recommended applicator is a UNi-PRO Sheepskin Bag And Render Mitt. To paint or cut in the sides, you can use an ordinary paint brush to apply the textured paint. However, allow me to double check with Dulux if it's possible to use any other applicators. As soon as I have more information, I'll get back to you.

Thank you for your patience.

Eric

https://www.workshop.bunnings.com.au/discussion/comment/76800#Comment_76800

Hello @Rohan123

I've contacted the Dulux technical department regarding the textured paint, and they've informed me that they don't recommend using the textured paint on a flat Colorbond surface. Unfortunately, it is only compatible with rough masonry surfaces such as brick and rendered walls. My apologies if you've already settled on this solution.

I can only recommend the other solutions suggested as the textured paint won't work on a Colorbond surface.

Install sarking or Insulation batts to be cladded over with HardieFlex.
Use Moroday 750 x 10mm x 1.8m Adhesive Foam Roll.
Build a proper ceiling enclosure.
Use Bristol 750mm Wall Industrial Wall Fan to increase wind flow, and dry off the condensation before it forms.

If I think of other possible solutions for your condensation issue, I'll post it here.

If you need further assistance, please let me know.

Eric

Veggiemate

https://www.workshop.bunnings.com.au/discussion/comment/102372#Comment_102372

Hello Eric
I have an enclosed outdoor patio approx 5m x 4m (brick walls and glass windows) and am also experiencing condensation under my Trimdeck roof despite the patio being reasonably weatherproof. Didn't really wish to build a structure to accommodate insulation due to the low roof height. So the Moroday adhesive foam roll sounds like a good idea to try out. However, the black colour would really darken the area and Moroday doesn't appear to make a white coloured roll. So I'm now thinking of using an adhesive foam roll with aluminium foil on the underside. However, would I simply be transferring the condensation from the underside of the roof to the underside of the foil by using this method?
Thanks
Cameron

https://www.workshop.bunnings.com.au/discussion/comment/122053#Comment_122053

Welcome to the Bunnings Workshop community @Veggiemate. It's terrific to have you join us, and many thanks for your question about patio insulation.

The core issue here is that condensation occurs when warm, moisture-laden air comes into contact with a cold surface—like the underside of your Trimdek roofing. Once that surface drops below the dew point, the moisture in the air condenses into water droplets, which is what’s causing the drips.

The purpose of insulation—like the Moroday foam roll—is to isolate that cold metal surface from the moist air below. It acts as a thermal break, reducing the temperature difference that causes condensation in the first place. By covering the cold metal with an insulating layer, you're essentially preventing the air from touching a surface cold enough to reach dew point.

Now, switching to a foam with an aluminium foil backing can be a bit of a trade-off. The aluminium surface itself can get quite cold, especially if it’s exposed and facing down into your patio area. So while it might stop condensation forming on the roof sheet directly, you might just shift the problem to the underside of the foil if it cools enough and comes into contact with humid air. This is particularly true if the foil isn’t insulated well enough from the roof sheet above.

To minimise this, it’s important to make sure the foil-faced insulation has enough foam thickness to properly isolate that foil from the cold roof metal. A tight bond and good coverage also help prevent air pockets and thermal bridging, which can make condensation worse.

Please let me know if you have any questions.

Mitchell

Veggiemate

https://www.workshop.bunnings.com.au/discussion/comment/130095#Comment_130095

Hi Mitchell
Thanks so much for your prompt response. So it looks like I won't be using a foil backed insulation roll 🙂 Likewise with the Foilboards.
So the thought now is to using some large foam sheets and glue to the underside of the Trimdeck. Discovered some closed cell foam sheets made from Polyethylene and blended copolymers by MSTOR in Melbourne. They come in a few different colours/sizes including white. Plus there is the option of a self-adhesive backing - https://mstor.com.au/products/pe-foam-sheet-2400mm-x-1200mm?variant=46680252907827
Has Bunnings dealt with this company before and is it possible to place a special order via one of your stores?
Cheers
Cameron