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How to fix roof overhang that is too short?

ethanc

Hello,

I have a situation where capillary action might be happening underneath my roof sheets due to the roof overhang being too short over the gutter. I was wondering what your input was to fix this as I have read online that it involves fitting another sheet over or installing a drip edge. A plumber quoted me about 7k to replace the flashings but it is too expensive as I think there is a cheaper alternative to extend the overhang. Thank you.

Kind regards,

Ethan

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MitchellMc

Welcome to the Bunnings Workshop community @ethanc. It's wonderful to have you join us and many thanks for your question on roofing.

Ideally, whether the roof overhang is shorter like yours (which, from the photo, doesn't actually look excessively short) or much longer, water droplets shouldn't be able to cling to the underside of the roof sheeting and travel back into the roof by capillary action.

One possibility is that the ends of the roof sheets simply need to be crimped down slightly more. This creates a more pronounced drip edge, encouraging water to fall cleanly into the gutter rather than tracking back underneath the sheeting.

Water can't run uphill under normal circumstances, so it's a little unusual that this is happening. If the roof has been constructed with the correct fall in accordance with the manufacturer's specifications and building requirements, it should be difficult for water to track back beneath the sheets unless it's being driven by strong winds.

Extending the roof sheets is another option, but I'm not convinced it would necessarily solve the problem. If water is able to cling to the underside of the sheeting in its current configuration, it could potentially continue doing the same even with a longer overhang.

Do you know the pitch of the roof, or have you noticed whether this only occurs during heavy rain or windy conditions? That information would help narrow down the cause.

If the sheeting itself is the issue, I'd be more inclined to look at fitting a drip edge or having the sheet ends crimped further to improve the water break before considering more extensive work such as replacing flashings. Regarding the flashings, if the plumber was going to replace them, it sounds as if they believe they are the issue and not the overhang of the sheet.

Let me tag @Nailbag to see if he has any thoughts.

Please let me know if you have any questions.

Mitchell

ethanc

Hi Mitch,

Thanks for having me. The plumber initially said that the roof sheets needed to be replaced because of capillary action which I don't think substantiates complete removal of the entire roof as the roof sheets are in good condition. I have been thinking of doing the drip edge or crimping it down. It leaks into my garage a bit during windy/rainy conditions but not a huge leak, just a few drops and it stops. I am not too sure of the pitch but it is generally straight just above my garage.

Kind regards,

Ethan

EricL

Hi @ethanc

Just to double check on the fall of the roof, I propose placing a long spirit level on the surface to confirm that there is a proper fall in the roof. I agree with my teammates analysis that capillary action should not be happening unless the fall is very shallow.

Please let us know what you find out once you've done the checking the fall.

Eric

Nailbag

Hi @ethanc

I agree that replacing the roof sheets at $4K is out of the question as I don't believe like @MitchellMc thats the issue. The end crimps look fine too. So, potentially whats left is that the fall of the roofline is possibly too shallow as that would definitely cause a back flow under the sheets.

I've had to deal with a similar issue myself on my last house due to the sheets running very short. I'm no plumber so it wasn't probably what a plumber would do to resolve the issue. But what I did worked perfectly and for around $50. My roof was corrugated so, I needed to first remove the last row of screws. Then I used adhesives backed flashing that I had ripped about a 1/3rd off and stuck that to the underside of the profile. I angled the end downward quite steeply. This prevented water from any underflow and direct it all well into the gutter. It might be worth a crack?

Nailbag

ethanc

Thanks Eric and Nailbag for your suggestions.

As you can tell, I am not an expert nor a handyman so all these terms or tools are a bit confusing. For what it's worth, do you think I should try and bend the crimps to an angle first to test whether it will still leak? The plumber recently installed a PVC pipe spreader because I had a downpipe that was discharging water which he thinks is the cause of the leak into garage.

Kind regards

Ethan

EricL

Hello @ethanc

Personally, I don't think the crimps are the cause of the leak. I suggest having a good look at @Nailbag's suggestion of adding flashing under your roof. I believe this will catch any catch any errant raindrops that are travelling backwards. But as I mentioned its best to check with a https://www.bunnings.com.au/stanley-1200mm-high-impact-abs-resin-spirit-level_p5660383 to see if the roof has a proper fall.

Eric

ethanc

hi guys,

it’s a 1 degree pitch

Kind regards

Ethan

EricL

Hello @ethanc

For a 1-degree pitch, you will need approximately a 35 mm total drop across a two-meter run. Corrugated roofing requires a minimum of 5 degrees, if the total drop is too shallow, then water will not flow properly to the gutter.

Eric

MikeTNZ

Hey Folks,

I may have come into this a bit late, but, here are what little thoughts I have on this.

There is moss on the end of the sheeting, that would suggest that there is either water pooling there or that part of the roof doesn't get a great deal of sunlight?

That down-pipe transition, where it changes from rectangular/square to the PVC pipe, the pipe that comes out of that should be rotated so that it flows into the ducting below, not onto the roof, I suspect that this water comes from a roof above the one we see?, I also have no idea why there seems to be a cap over the end of the pipe, maybe this is to slow down the flow, but this can cause issues with the pipe being flooded and air-locking during heavy rainfall, causing heavy flow once air eventually gets into the pipe from above, you could also extend that and put an elbow on the end to get it in the centre of the ducting below, so that the roof only drains the run-off that it has by itself.

Is it just me or are there no fasteners holding the roofing profiles down to the timber underneath?, I understand that there are clip systems for this sort of profile, but in wet and windy weather, this could be compounding the problem, possibly, I don't know.

If any one of them clips have become compromised, you can end up with a gap that will let wind-driven rain in, which could look the same as Capillary effect, the best way to check this would be to walk over the edge of that roof and see if any of the profiles move more that you would expect them to.

With respect to Capillary effect, for those that don't know about this, it is where water/moisture will find any gap between building members and will travel in the opposite direction to gravity, getting into places where you wouldn't think it would.

New Zealand had this issue a couple of decades ago with the "Leaky Homes" debacle, where poorly trained builders/apprentices never sealed things adequately and a lot of building materials got wet and mouldy where they should not have done.

I hope that these thoughts have been of use to someone.

Cheers,

Mike T.