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How to fill gap in roofing to prevent leaks?

I got a lean to built to provide some cover over my clothes drying area so I don’t have to bring the clothes in when it rains. However this gap in the roofing is letting water in especially during heavy downpours . The gaps are quite large at some locations up to 25mm. The gap is not even across the length of the lean to roofline, in most places it butts right up to the rubber seal.

What’s the best solution here? Additional flashing between the gutter and the lean to roof or some water proof outdoor seal?

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MitchellMc

Hi @rajenzed,

It would helpful to see the end profile of the roof sheeting, because the fix you choose depends a lot on the shape of the sheet and how it meets the existing gutter line. Normally, metal sheet sits hard up against the rubber gutter gasket, that gasket creates a reasonably reliable seal. In your case the gap shows there is a bit of an angle or alignment issue, so the sheet never properly compresses against the rubber. That is why water is getting in during heavy downpours.

One option is to install a foam sealing strip along the top edge of the roofing sheet where it meets the support structure. These foam infills are profiled to match common roof sheet patterns and act as a physical barrier, stopping water before it even reaches the rubber gasket. If there is a suitable foam infill for your sheet profile, this can be a simple and effective fix. If no matching foam exists or the gap varies too much in size, an additional piece of flashing can be installed between the mount and the lean to roof to bridge the gap and push water outward. That creates a controlled path for water to run off instead of forcing its way back inside. Once we see the roof profile, it will be easier to suggest the most suitable option for your setup.

Please let me know if you have any questions.

Mitchell

rajenzed

https://www.workshop.bunnings.com.au/discussion/comment/59911#Comment_59911

Thanks Mitchell.

its a Stratcp Prodek profile.

Would the foam filler go between the roofing sheet and the top flange of the C channel as marked in blue? Any sealant required?

EricL

https://www.workshop.bunnings.com.au/discussion/comment/92401#Comment_92401

Hello @rajenzed

Thank you for sharing those extra photos of your roof. Yes, the sealer will go into that gap where you have marked blue. I propose measuring the width of the rise and fall of the valleys on your roofing sheet and comparing it to the Crommelin 940mm Trimdeck Ridge Superseal to see if it is compatible. You can also try using a flat generic sealer such as the Crommelin 30 x 30mm x 2m Superseal, it comes in a thicker size should you need it. The flat generic sealer does not come with any cuts and is simply pushed into the gap. It does not require any sealant.

Please note that if you are using a ladder, I suggest having a quick look at this safety guide - How to use ladder safely by @Adam_W.

If you need further assistance, please let us know.

Eric

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